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  • 151.
    Jaros, Adam
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Berglund, Kris
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Acetate adaptation of clostridia tyrobutyricum for improved fermentation production of butyrate2013Inngår i: SpringerPlus, E-ISSN 2193-1801, Vol. 2, nr 1Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Clostridium tyrobutyricum ATCC 25755 is an acidogenic bacterium capable of utilizing xylose for the fermentation production of butyrate. Hot water extraction of hardwood lingocellulose is an efficient method of producing xylose where autohydrolysis of xylan is catalysed by acetate originating from acetyl groups present in hemicellulose. The presence of acetic acid in the hydrolysate might have a severe impact on the subsequent fermentations. In this study the fermentation kinetics of C. tyrobutyricum cultures after being classically adapted for growth at 26.3 g/L acetate equivalents were studied. Analysis of xylose batch fermentations found that even in the presence of high levels of acetate, acetate adapted strains had similar fermentation kinetics as the parental strain cultivated without acetate. The parental strain exposed to acetate at inhibitory conditions demonstrated a pronounced lag phase (over 100 hours) in growth and butyrate production as compared to the adapted strain (25 hour lag) or non-inhibited controls (0 lag). Additional insight into the metabolic pathway of xylose consumption was gained by determining the specific activity of the acetate kinase (AK) enzyme in adapted versus control batches. AK activity was reduced by 63% in the presence of inhibitory levels of acetate, whether or not the culture had been adapted.

  • 152.
    Jaros, Adam
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Berglund, Kris
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Effect of acetate on fermentation production of butyrate2012Inngår i: Cellulose Chemistry and Technology, ISSN 0576-9787, Vol. 46, nr 5-6, s. 341-347Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A carbon source for the fermentation production of butyrate is xylose extracted from ligno-cellulosic material by hot water extraction. Although this auto-hydrolysis of hemicellulose can provide a low-cost source of xylose, the process generates a high level of acetic acid that might inhibit subsequent fermentations. This study focuses on the effects of acetate on the production of butyrate from xylose by batch fermentations with a selected strain Clostridium tyrobutyricum.At initial acetate concentrations of 17.6 g L-1 and 26.3 g L-1 in the media, C. tyrobutyricum cultures exhibited a lag phase (45 and 118 hours, respectively) in terms of sugar consumption, butyrate production and cell biomass growth, lowering the overall production rate. Butyrate fermentations performed with high concentrations of acetate in the media demonstrated a re-uptake of acetate into the butyrate production pathway and after the lag phase, all cultures adapted to the inhibitory acetate, which increased the final butyrate yields by 12.6% (32.6 g L-1 compared to 28.5 g L-1).

  • 153.
    Johansson, Simon
    et al.
    Nestec Ltd, Nestlé Research Center.
    Diehl, Bernd
    Spectral Services AG, Köln.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Austin, Sean
    Nestec Ltd, Nestlé Research Center.
    Vafialdi, Christina
    Nestec Ltd, Nestlé Research Center.
    Oligosaccharide synthesis in Fruit Juice Concentrates using a Glucansucrase from Lactobacillus reuteri 1802016Inngår i: Food and Bioproducts Processing, ISSN 0960-3085, E-ISSN 1744-3571, Vol. 98, s. 201-209Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The application of the glucansucrase GTF180 from Lactobacillus reuteri 180 in fruit juice concentrates for the synthesis of glucooligosaccharides was investigated. Reaction parameters such as temperature, pH, substrate and enzyme loading, Ca+2 addition and incubation time were investigated in high concentration sucrose solutions. The optimum conditions (50 °C, pH 4.5, enzyme loading 14.47 U/gsucrose with 1 mM CaCl2, undiluted fruit juice concentrates) were applied in apple and orange juice concentrates. More than 95% of the intrinsic sucrose was converted to oligosaccharide products after 90 min. The main products were leucrose, isomaltose and isomaltotriose. The enzyme was deactivated during standard fruit juice pasteurization conditions (95 °C, 15 sec). The oligosaccharides were stable during the pasteurization process, showing a good potential for industrial applications. DOSY NMR analysis of the enzymatically modified fruit juice concentrates showed that α1→6 glycosidic linkages are predominant in apple juice, while products in orange juice possess both α1→6 and α1→3 glycosidic linkages. The presence of α1→2 glycosidic linkages were also observed at a lower extent

  • 154.
    Jonfelt, Clara
    et al.
    Uppsala University, Sweden.
    Zambrano, Jesús
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Lindblom, Erik
    Stockholm Vatten, Sweden.
    Nehrenheim, Emma
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Key parameters for modelling Anammox process with N2O emissions2017Inngår i: French Federation of Biotechnology - Bioreactors Symposium 2017: Innovative approaches in bioreactors design and operation, France, 2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, a sensitivity analysis and a calibration were applied to a recent published model used to replicate N2O emissions in an Anammox process of a moving-bed biofilm reactor (MBBR). The model used in this study was designed to replicate a one-stage nitrification-Anammox system in a MBBR at Hammarby-Sjöstad pilot plant (Stockholm, Sweden), whichtreats of anaerobic digestion liquor. The aeration was intermittently (45/15 minutes - on/off). During the aeration, a 1.5 mg/L DO set-point was set. Three main measurements wereobtained: NH4 in water, N2O in both water and gas phase.The sensitivity analysis was done via the one-at-a-time method, where one parameter at a timeis changed (in our case, 10%) from its nominal value and the model output is quantified. Next,the most sensitive parameters were used in the model calibration. Results indicate that the biofilm porosity (η [-]), biofilm density (ρ [gTS/m3]), maximum biofilmthickness (Lmax [mm]) and boundary layer thickness of the biofilm (L0 [μm]) were the mostsensitive parameters of the model. These parameters performed the model calibration.

  • 155.
    Kalogiannis, Konstantinos G
    et al.
    Chemical Process and Energy Resources Institute (CPERI), Centre for Research and Technology Hellas (CERTH), 6th km Harilaou-Thermi Rd, 57001 Thessaloniki, Greece.
    Matsakas, Leonidas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Aspden, James
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Lappas, Angelos A
    Chemical Process and Energy Resources Institute (CPERI), Centre for Research and Technology Hellas (CERTH), 6th km Harilaou-Thermi Rd, 57001 Thessaloniki, Greece.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Acid Assisted Organosolv Delignification of Beechwood and Pulp Conversion towards High Concentrated Cellulosic Ethanol via High Gravity Enzymatic Hydrolysis and Fermentation2018Inngår i: Molecules, ISSN 1420-3049, E-ISSN 1420-3049, Vol. 23, nr 7, artikkel-id 1647Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: Future biorefineries will focus on converting low value waste streams to chemical products that are derived from petroleum or refined sugars. Feedstock pretreatment in a simple, cost effective, agnostic manner is a major challenge.

    Methods: In this work, beechwood sawdust was delignified via an organosolv process, assisted by homogeneous inorganic acid catalysis. Mixtures of water and several organic solvents were evaluated for their performance. Specifically, ethanol (EtOH), acetone (AC), and methyl- isobutyl- ketone (MIBK) were tested with or without the use of homogeneous acid catalysis employing sulfuric, phosphoric, and oxalic acids under relatively mild temperature of 175 °C for one hour.

    Results: Delignification degrees (DD) higher than 90% were achieved, where both AC and EtOH proved to be suitable solvents for this process. Both oxalic and especially phosphoric acid proved to be good alternative catalysts for replacing sulfuric acid. High gravity simultaneous saccharification and fermentation with an enzyme loading of 8.4 mg/gsolids at 20 wt.% initial solids content reached an ethanol yield of 8.0 w/v%.

    Conclusions: Efficient delignification combining common volatile solvents and mild acid catalysis allowed for the production of ethanol at high concentration in an efficient manner

  • 156.
    Kalogiannis, Konstantinos G.
    et al.
    Chemical Process and Energy Resources Institute (CPERI), Centre for Research and Technology Hellas (CERTH), Thessaloniki, Greece.
    Matsakas, Leonidas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Lappas, Angelos A.
    Chemical Process and Energy Resources Institute (CPERI), Centre for Research and Technology Hellas (CERTH), Thessaloniki, Greece.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Aromatics from Beechwood Organosolv Lignin through Thermal and Catalytic Pyrolysis2019Inngår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 12, nr 9, artikkel-id 1606Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Biomass fractionation, as an alternative to biomass pretreatment, has gained increasing research attention over the past few years as it provides separate streams of cellulose, hemicellulose, and lignin. These streams can be used separately and can provide a solution for improving the economics of emerging biorefinery technologies. The sugar streams are commonly used in microbial conversions, whereas during recent years lignin has been recognized as a valuable compound as it is the only renewable and abundant source of aromatic chemicals. Successfully converting lignin into valuable chemicals and products is key in achieving both environmental and economic sustainability of future biorefineries. In this work, lignin retrieved from beechwood sawdust delignification pretreatment via an organosolv process was depolymerized with thermal and catalytic pyrolysis. ZSM-5 commercial catalyst was used in situ to upgrade the lignin bio-oil vapors. Lignins retrieved from different modes of organosolv pretreatment were tested in order to evaluate the effect that upstream pretreatment has on the lignin fraction. Both thermal and catalytic pyrolysis yielded oils rich in phenols and aromatic hydrocarbons. Use of ZSM-5 catalyst assisted in overall deoxygenation of the bio-oils and enhanced aromatic hydrocarbons production. The oxygen content of the bio-oils was reduced at the expense of their yield. Organosolv lignins were successfully depolymerized towards phenols and aromatic hydrocarbons via thermal and catalytic pyrolysis. Hence, lignin pyrolysis can be an effective manner for lignin upgrading towards high added value products

  • 157.
    Kanelli, Maria
    et al.
    Laboratory of Polymer Technology, School of Chemical Engineering, National Technical University of Athens.
    Douka, Aliki
    Laboratory of Polymer Technology, School of Chemical Engineering, National Technical University of Athens.
    Vouyiouka, Stamatina
    Laboratory of Polymer Technology, School of Chemical Engineering, National Technical University of Athens.
    Papaspyrides, Constatine D.
    Laboratory of Polymer Technology, School of Chemical Engineering, National Technical University of Athens.
    Topakas, Evangelos
    BIOtechMASS Unit, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Papaspyridi, Lefki-Maria
    National Technical University of Athens.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Production of biodegradable polyesters via enzymatic polymerization and solid state finishing2014Inngår i: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 131, nr 19, artikkel-id 40820Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The synthesis of aliphatic polyesters (PEs) derived from diols (1,4-butanediol and 1,8-octanediol) and diacids or their derivatives (diethyl succinate, sebacic acid, 1,12-dodecanedioic acid, and 1,14-tetradecanedioic acid) was achieved in order to produce poly(butylene succinate) (PE 4.4), poly(octylene sebacate) (PE 8.10), poly(octylene dodecanate) (PE 8.12), and poly(octylene tetradecanate) (PE 8.14). The herein suggested procedure involved two stages, both sustainable and in accordance with the principles of "green" polymerization. The first comprised an enzymatic prepolymerization under vacuum, in the presence of diphenylether as solvent using Candida antarctica lipase B as biocatalyst, whereas a low-temperature postpolymerization step [solid state polymerization (SSP)] followed in order to upgrade the PEs quality. In the enzymatically synthesized prepolymers, the range of number-average molecular weight attained was from 3700 to 8000 g/mol with yields reaching even 97%. Subsequently, SSP of PE 4.4 and 8.12 took place under vacuum or flowing nitrogen and lasted 10-48 h, at temperatures close to the prepolymer melting point (Tm -  TSSP varied between 4°C and 14°C). The solid state finishing led to increase in the molecular weight depending on the prepolymer type, and it also contributed to improvement of the physical characteristics and the thermal properties of the enzymatically synthesized PEs

  • 158.
    Kanelli, Maria
    et al.
    IndBioCat Group, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Mandic, Mina
    Institute of Molecular Genetics and Genetic Engineering, University of Belgrade.
    Kalakona, Margarita
    IndBioCat Group, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athen.
    Vasilakos, Sozon
    Materials Industrial Research and Technology Center S.A., Athens.
    Kekos, Dimitris
    IndBioCat Group, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Nikodinovic-Runic, Jasmina
    Institute of Molecular Genetics and Genetic Engineering, University of Belgrade.
    Topakas, Evangelos
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. IndBioCat Group, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Microbial Production of Violacein and Process Optimization for Dyeing Polyamide Fabrics With Acquired Antimicrobial Properties2018Inngår i: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 9, artikkel-id 1495Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present study, crude bacterial extract containing violacein is investigated for the preparation of antimicrobial polyamide fabrics. The optimal culture conditions of Janthinobacterium lividum (JL) for maximum biomass and violacein production were found to be 25°C, pH 7.0, while the addition of ampicillin of 0.2 mg mL-1 in the small scale increased violacein production 1.3-fold. In scale-up trials, the addition of 1% (v/v) glycerol in a fed-batch bioreactor, resulted in fivefold extracted crude violacein increase with final concentration of 1.828 g L-1. Polyamide 6.6 fabrics were dyed following three different processes; through simultaneous fermentation and dyeing (SFD), by incubating the fabric in the sonicated bacterial culture after fermentation and by using cell-free extract containing violacein. Maximum color change (ΔE) and color strength (K/S) obtained for SFD fabrics were 74.81 and 22.01, respectively, while no alteration of fastness and staining of dye at acid and alkaline perspiration or at water was indicated. The dyed fabrics presented significant antifungal activity against Candida albicans, C. parapsilosis, and C. krusei, as well as antibacterial properties against Escherichia coli, Staphylococcus aureus, and the S. aureus MRSA. We have shown that J. lividum cultures can be successfully used for violacein production and for simultaneous dying of fabrics resulting in dyed fabrics with antimicrobial properties without utilization of organic solvents.

  • 159.
    Kanelli, Maria
    et al.
    National Technical University of Athens, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Vasilakos, Sozon
    MIRTEC, Materials Industrial Research & Technology Center S.A.
    Ladas, Spyridon
    Surface Science Laboratory, Department of Chemical Engineering, University of Patras.
    Symianikis, Emmanouil
    Surface Science Laboratory, Department of Chemical Engineering, University of Patras.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Topakas, Evangelos
    National Technical University of Athens, School of Chemical Engineering, National Technical University of Athens, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Surface modification of polyamide 6.6 fibers by enzymatic hydrolysis2016Inngår i: Process Biochemistry, ISSN 1359-5113, E-ISSN 1873-3298, Vol. 59 A, s. 97-103Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Synthetic fibers are used extensively in textile industry, however, their high hydrophobicity is a drawback that needs to be considered. The decrease of hydrophobicity can be achieved via a ‘green” root using enzymes as biocatalysts. In this study, the enzymatic surface modification of polyamide (PA) 6.6 fabric was studied with the use of the commercial protease Alcalase 2.4 L at optimal conditions. The modified fabrics were studied via dyeing parameters K/S and ΔΕ values. For treatment at 40–60 °C and pH 8 ΔE was found to be approximately 14 and K/S was 1.24-fold increased. Additionally, the enzymatic surface modification of PA textile was justified using different spectroscopy techniques, such as FTIR-ATR and XPS. FTIR-ATR indicated alterations of Cdouble bond; length as m-dashO and N-H band intensities, while via XPS, there proved to be differences in relative intensities of carbon component peaks. Finally, thermogravimetric and mechanical tests were also conducted to prove the non-degradation of the properties of the bulk material. In conclusion, the investigated enzymatic process increased the hydrophilicity with 2.7-fold increased water absorbency and 1.24-fold enhanced color strength of PA textiles, while maintaining the thermal and mechanical properties of the bulk synthetic material.

  • 160.
    Kanelli, Maria
    et al.
    National Technical University of Athens.
    Vasilakos, Sozon
    MIRTEC, Materials Industrial Research & Technology Center S.A.
    Nikolaivits, Efstratios
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Ladas, Spyridon
    Surface Science Laboratory, Department of Chemical Engineering, University of Patras.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Topakas, Evangelos
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Surface modification of poly(ethylene terephthalate) (PET) fibers by a cutinase from Fusarium oxysporum2015Inngår i: Process Biochemistry, ISSN 1359-5113, E-ISSN 1873-3298, Vol. 50, nr 11, s. 1885-1892Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Synthetic polyester fabrics occupy a great part of the textile industry production satisfying variable ordinary needs. Nonetheless, their high hydrophobicity constitutes an important weakness that impedes process manufacture, as well as permeability and evaporation of sweat when used in clothing industry. The enzymatic treatment of these materials is a modern and eco-friendly procedure that aims at the increase of the hydrophilicity through superficial modification. In this study, the enzymatic surface hydrolysis of poly(ethylene terephthalate) (PET) fabric is succeeded using a recombinant cutinase from Fusarium oxysporum. The effect of various parameters is studied for the enzymatic modification of PET, such as temperature, pH, enzyme loading and reaction time. The optimal parameters are found to be 40 °C, pH 8, and 1.92 mg enzyme loading per gram of fabric. The controlled enzymatic hydrolysis of PET textile is further confirmed and characterized using various spectroscopic and analytical methods, including Fourier Transform Infrared (FT-IR) in the Attenuated Total Reflectance mode (ATR) and X-ray photoelectron spectroscopy (XPS). Tensile test and dyeability analyses were also employed achieving a K/S increase up to 150%, confirming the successful surface modification without degrading the quality of the starting material.

  • 161.
    Karnaouri, Anthi C
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Antonopoulou, Io
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Topakas, Evangelos
    National Technical University of Athens.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Genomic insights into the fungal lignocellulolytic system of Myceliophthora thermophila2014Inngår i: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 5, artikkel-id 5.281Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    he microbial conversion of solid cellulosic biomass to liquid biofuels may provide a renewable energy source for transportation fuels. Cellulolytic fungi represent a promising group of organisms, as they have evolved complex systems for adaptation to their natural habitat. The filamentous fungus Myceliophthora thermophila constitutes an exceptionally powerful cellulolytic microorganism that synthesizes a complete set of enzymes necessary for the breakdown of plant cell wall. The genome of this fungus has been recently sequenced and annotated, allowing systematic examination and identification of enzymes required for the degradation of lignocellulosic biomass. The genomic analysis revealed the existence of an expanded enzymatic repertoire including numerous cellulases, hemicellulases and enzymes with auxiliary activities, covering the most of the recognized CAZy families. Most of them were predicted to possess a secretion signal and undergo through post translational glycosylation modifications. These data offer a better understanding of activities embedded in fungal lignocellulose decomposition mechanisms and suggest that M. thermophila could be made usable as an industrial production host for cellulolytic and hemicellulolytic enzymes

  • 162.
    Karnaouri, Anthi C.
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Antonopoulou, Io
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Zerva, Anastasia
    Biotechnology Laboratory, Department of Synthesis and Development of Industrial Processes, School of Chemical Engineering, National Technical University of Athens, Athens, Greece.
    Dimarogona, Maria
    Section of Process and Environmental Engineering, Department of Chemical Engineering, University of Patras, Patras, Greece.
    Topakas, Evangelos
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Biotechnology Laboratory, Department of Synthesis and Development of Industrial Processes, School of Chemical Engineering, National Technical University of Athens, Athens, Greece.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Thermophilic enzyme systems for efficient conversion of lignocellulose to valuable products: Structural insights and future perspectives for esterases and oxidative catalysts2019Inngår i: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 279, s. 362-372Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thermophilic enzyme systems are of major importance nowadays in all industrial processes due to their great performance at elevated temperatures. In the present review, an overview of the current knowledge on the properties of thermophilic and thermotolerant carbohydrate esterases and oxidative enzymes with great thermostability is provided, with respect to their potential use in biotechnological applications. A special focus is given to the lytic polysaccharide monooxygenases that are able to oxidatively cleave lignocellulose through the use of oxygen or hydrogen peroxide as co-substrate and a reducing agent as electron donor. Structural characteristics of the enzymes, including active site conformation and surface properties are discussed and correlated with their substrate specificity and thermostability properties.

  • 163.
    Karnaouri, Anthi C
    et al.
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Evangelos, Topakas
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Cloning, expression, and characterization of a thermostable GH7 endoglucanase from Myceliophthora thermophila capable of high-consistency enzymatic liquefaction2014Inngår i: Applied Microbiology and Biotechnology, ISSN 0175-7598, E-ISSN 1432-0614, Vol. 98, nr 1, s. 231-242Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An endoglucanase gene from the thermophilic fungus Myceliophthora thermophila, belonging to the glycoside hydrolase family 7, was functionally expressed in methylotrophic yeast Pichia pastoris. The putative endoglucanase from the genomic DNA was successfully cloned in P. pastoris X-33 and the recombinant enzyme was purified to its homogeneity (65 kDa) and subsequently characterized. Substrate specificity analysis revealed that the enzyme exhibits high activity on substrates containing β-1,4-glycosidic bonds such as carboxymethyl cellulose, barley β-glucan, and cello-oligosaccharides, as well as activity on xylan-containing substrates, including arabinoxylan and oat spelt xylan. MtEG7a was proved to liquefy rapidly and efficiently pretreated wheat straw, indicating its key role to the initial step of hydrolysis of high-solids lignocellulose substrates. High thermostability of the endoglucanase reflects potential commercial significance of the enzyme

  • 164.
    Karnaouri, Anthi C
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Department of Chemical Sciences and Technologies, Via della Ricerca Scientifica, University of Rome Tor Vergata.
    Lange, Heikko
    Department of Chemical Sciences and Technologies, Via della Ricerca Scientifica, University of Rome Tor Vergata.
    Crestini, Claudia
    Department of Chemical Sciences and Technologies, Via della Ricerca Scientifica, University of Rome Tor Vergata.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Chemoenzymatic Fractionation and Characterization of Pretreated Birch Outer Bark2016Inngår i: ACS Sustainable Chemistry and Engineering, ISSN 2168-0485, Vol. 4, nr 10, s. 5289-5302Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, the application of different chemical and enzymatic treatment methods for the fractionation of the birch outer bark components was evaluated. More specifically, untreated and steam exploded, hydrothermally and organosolv treated bark samples were incubated with enzyme mixtures that consisted of cellulases, hemicellulases and esterases, and the effect of enzymes was analyzed with 31P NMR and {13C-1H} HSQC. The biocatalysts performed the cleavage of ester bonds resulting in reduction of methoxy and aliphatic groups in the remaining solid fraction, whereas the aromatic fraction remained intact. Moreover, the suberin and lignin fraction were isolated chemically and their properties were characterized by gas chromatography (GC-MS), 31P NMR, {13C-1H} HSQC and gel permeation chromatography (GPC). It was demonstrated that the lignin fraction was enriched in guaiacyl phenolics but still contained some associated aliphatic acids and carbohydrates, whereas the suberin fraction presented a polymodal pattern of structures with different molecular weight distributions. This work will help in getting a deeper fundamental knowledge of the bark structure, the intermolecular connection between lignin and suberin fractions, as well as the potential use of enzymes in order to degrade the recalcitrant bark structure toward its valorization.

  • 165.
    Karnaouri, Anthi C
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Matsakas, Leonidas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Topakas, Evangelos
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Department of Chemical Engineering, Biotechnology Laboratory, National Technical University of Athens.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Development of Thermophilic Tailor-Made Enzyme Mixtures for the Bioconversion of Agricultural and Forest Residues2016Inngår i: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 7, artikkel-id 177Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Even though the main components of all lignocellulosic feedstocks include cellulose, hemicellulose, as well as the protective lignin matrix, there are some differences in structure, such as in hardwoods and softwoods, which may influence the degradability of the materials. Under this view, various types of biomass might require a minimal set of enzymes that has to be tailor-made. Partially defined complex mixtures that are currently commercially used are not adapted to efficiently degrade different materials, so novel enzyme mixtures have to be customized. Development of these cocktails requires better knowledge about the specific activities involved, in order to optimize hydrolysis. The role of filamentous fungus Myceliophthora thermophila and its complete enzymatic repertoire for the bioconversion of complex carbohydrates has been widely proven. In this study, four core cellulases (MtCBH7, MtCBH6, MtEG5, and MtEG7), in the presence of other four “accessory” enzymes (mannanase, lytic polyssacharide monooxygenase MtGH61, xylanase, MtFae1a) and β-glucosidase MtBGL3, were tested as a nine-component cocktail against one model substrate (phosphoric acid swollen cellulose) and four hydrothermally pretreated natural substrates (wheat straw as an agricultural waste, birch, and spruce biomass, as forest residues). Synergistic interactions among different enzymes were determined using a suitable design of experiments methodology. The results suggest that for the hydrolysis of the pure substrate (PASC), high proportions of MtEG7 are needed for efficient yields. MtCBH7 and MtEG7 are enzymes of major importance during the hydrolysis of pretreated wheat straw, while MtCBH7 plays a crucial role in case of spruce. Cellobiohydrolases MtCBH6 and MtCBH7 act in combination and are key enzymes for the hydrolysis of the hardwood (birch). Optimum combinations were predicted from suitable statistical models which were able to further increase hydrolysis yields, suggesting that tailor-made enzyme mixtures targeted toward a particular residual biomass can help maximize hydrolysis yields. The present work demonstrates the change from “one cocktail for all” to “tailor-made cocktails” that are needed for the efficient saccharification of targeted feed stocks prior to the production of biobased products through the biorefinery concept.

  • 166.
    Karnaouri, Anthi C
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Muraleedharan, Madhu Nair
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Dimarogona, Maria
    Biotechnology Laboratory, Department of Synthesis and Development of Industrial Processes, School of Chemical Engineering, National Technical University of Athens.
    Topakas, Evangelos
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Sandgren, Mats
    Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences, Uppsala.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Recombinant expression of thermostable processive MtEG5 endoglucanase and its synergism with MtLPMO from Myceliophthora thermophila during the hydrolysis of lignocellulosic substrates2017Inngår i: Biotechnology for Biofuels, ISSN 1754-6834, E-ISSN 1754-6834, Vol. 10, nr 1, artikkel-id 126Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

     Background

    Filamentous fungi are among the most powerful cellulolytic organisms in terrestrial ecosystems. To perform the degradation of lignocellulosic substrates, these microorganisms employ both hydrolytic and oxidative mechanisms that involve the secretion and synergism of a wide variety of enzymes. Interactions between these enzymes occur on the level of saccharification, i.e., the release of neutral and oxidized products, but sometimes also reflected in the substrate liquefaction. Although the synergism regarding the yield of neutral sugars has been extensively studied, further studies should focus on the oxidized sugars, as well as the effect of enzyme combinations on the viscosity properties of the substrates.

    Results

    In the present study, the heterologous expression of an endoglucanase (EG) and its combined activity together with a lytic polysaccharide monooxygenase (LPMO), both from the thermophilic fungus Myceliophthora thermophila, are described. The EG gene, belonging to the glycoside hydrolase family 5, was functionally expressed in the methylotrophic yeast Pichia pastoris. The produced MtEG5A (75 kDa) featured remarkable thermal stability and showed high specific activity on microcrystalline cellulose compared to CMC, which is indicative of its processivity properties. The enzyme was capable of releasing high amounts of cellobiose from wheat straw, birch, and spruce biomass. Addition of MtLPMO9 together with MtEG5A showed enhanced enzymatic hydrolysis yields against regenerated amorphous cellulose (PASC) by improving the release not only of the neutral but also of the oxidized sugars. Assessment of activity of MtEG5A on the reduction of viscosity of PASC and pretreated wheat straw using dynamic viscosity measurements revealed that the enzyme is able to perform liquefaction of the model substrate and the natural lignocellulosic material, while when added together with MtLPMO9, no further synergistic effect was observed.

    Conclusions

    The endoglucanase MtEG5A from the thermophilic fungus M. thermophila exhibited excellent properties that render it a suitable candidate for use in biotechnological applications. Its strong synergism with LPMO was reflected in sugars release, but not in substrate viscosity reduction. Based on the level of oxidative sugar formation, this is the first indication of synergy between LPMO and EG reported.

  • 167.
    Karnaouri, Anthi C.
    et al.
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Paschos, Thomas
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Topakas, Evangelos
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Taouki, Ioanna
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Cloning, expression and characterization of an ethanol tolerant GH3 β-glucosidase from Myceliophthora thermophile2013Inngår i: PeerJ, ISSN 2167-8359, E-ISSN 2167-8359, artikkel-id 46Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The β-glucosidase gene bgl3a from Myceliophthora thermophila, member of the fungal glycosyl hydrolase (GH) family 3, was cloned and expressed in Pichia pastoris. The mature β-glucosidase gene, which results after the excision of one intron and the secreting signal peptide, was placed under the control of the strong alcohol oxidase promoter (AOX1) in the plasmid pPICZαC. The recombinant enzyme (90 kDa) was purified and characterized in order to evaluate its biotechnological potential. Recombinant P. pastoris efficiently secreted β-glucosidase into the medium and produced high level of enzymatic activity (41 U/ml) after 192 h of growth, under methanol induction. MtBgl3a was able to hydrolyze low molecular weight substrates and polysaccharides containing β-glucosidic residues. The Km was found to be 0.39 mM on p-β-NPG and 2.64 mM on cellobiose. Optimal pH and temperature for the p-β-NPG hydrolysis were 5.0 and 70 °C. The β-glucosidase exhibits a half life of 143 min at 60 °C. Kinetic parameters of inhibition were determined for D-glucose, D-xylose and D-gluconic acid, indicating tolerance of the enzyme for these sugars and oxidized products. The recombinant enzyme was stimulated by short chain alcohols and has been shown to efficiently synthesize methyl-D-glucoside in the presence of methanol due to its transglycosylation activity. The stability of MtBgl3a in ethanol was prominent, and it retained most of its original activity after we exposed it to 50% ethanol for 6 h. The high catalytic performance, good thermal stability and tolerance to elevated concentrations of ethanol, D-xylose and D-glucose qualify this enzyme for use in the hydrolysis of lignocellulosic biomass for biofuel production, as part of an efficient complete multi-enzyme cocktail.

  • 168.
    Karnaouri, Anthi C
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Effect of Different Pretreatment Methods on Birch Outer Bark: New Biorefinery Routes2016Inngår i: Molecules, ISSN 1420-3049, E-ISSN 1420-3049, Vol. 21, nr 4, artikkel-id 427Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A comparative study among different pretreatment methods used for the fractionation of the birch outer bark components, including steam explosion, hydrothermal and organosolv treatments based on the use of ethanol/water media, is reported. The residual solid fractions have been characterized by ATR-FTIR, 13C-solid-state NMR and morphological alterations afterpretreatment were detected by scanning electron microscopy. The general chemical composition of the untreated and treated bark including determination of extractives, suberin, lignin and monosaccharides was also studied. Composition of the residual solid fraction and relative proportions of different components, as a function of the processing conditions, could be established. Organosolv treatment produces a suberin-rich solid fraction, while duringhydrothermal and steam explosion treatment cleavage of polysaccharide bonds occurs. This work will provide a deeper fundamental knowledge of the bark chemical composition, thus increasing the utilization efficiency of birch outer bark and may create possibilities to up-scale the fractionation processes.

  • 169.
    Karnaouri, Anthi C
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Topakas, Evangelos
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. School of Chemical Engineering, National Technical University of Athens.
    Matsakas, Leonidas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Fine-tuned enzymatic hydrolysis of organosolv pretreated forest materials for the efficient production of cellobiose2018Inngår i: Frontiers in Chemistry, E-ISSN 2296-2646, Vol. 6, artikkel-id 128Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Non-digestible oligosaccharides (NDOs) are likely prebiotic candidates that have been related to the prevention of intestinal infections and other disorders for both humans and animals. Lignocellulosic biomass is the largest carbon source in the biosphere, therefore cello-oligosacharides (COS), especially cellobiose, are potentially the most widely available choice of NDOs. Production of COS and cellobiose with enzymes offers numerous benefits over acid-catalyzed processes, as it is milder, environmentally friendly and produces fewer by-products. Cellobiohydrolases (CBHs) and a class of endoglucanases (EGs), namely processive EGs, are key enzymes for the production of COS, as they have higher preference toward glycosidic bonds near the end of cellulose chains and are able to release soluble products. In this work, we describe the heterologous expression and characterization of two CBHs from the filamentous fungus Thermothelomyces thermophila, as well as their synergism with proccessive EGs for cellobiose release from organosolv pretreated spruce and birch. The properties, inhibition kinetics and substrate specific activities for each enzyme are described in detail. The results show that a combination of EGs belonging to Glycosyl hydrolase families 5, 6 and 9, with a CBHI and CBHII in appropriate proportions, can enhance the production of COS from forest materials, underpinning the potential of these biocatalysts in the production of NDOs.

  • 170.
    Katsimpouras, Constantinos
    et al.
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Bénarouche, Anaïs
    INRA, Aix Marseille Université, UMR1163, Polytech Marseille, 13288, Marseille.
    Navarro, David
    INRA, Aix Marseille Université, UMR1163, Polytech Marseille, 13288, Marseille.
    Karpusas, Michael
    Physics Laboratory, Department of Biotechnology, Agricultural University of Athens.
    Dimarogona, Maria
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Berrin, Jean-Guy
    INRA, Aix Marseille Université, UMR1163, Polytech Marseille, 13288, Marseille.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Topakas, Evangelos
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Enzymatic synthesis of model substrates recognized by glucuronoyl esterases from Podospora anserina and Myceliophthora thermophila2014Inngår i: Applied Microbiology and Biotechnology, ISSN 0175-7598, E-ISSN 1432-0614, Vol. 98, nr 12, s. 5507-5516, artikkel-id 10Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Glucuronoyl esterases (GEs) are recently discovered enzymes that are suggested to cleave the ester bond between lignin alcohols and xylan-bound 4-O-methyl-d-glucuronic acid. Although their potential use for enhanced enzymatic biomass degradation and synthesis of valuable chemicals renders them attractive research targets for biotechnological applications, the difficulty to purify natural fractions of lignin-carbohydrate complexes hampers the characterization of fungal GEs. In this work, we report the synthesis of three aryl alkyl or alkenyl d-glucuronate esters using lipase B from Candida antarctica (CALB) and their use to determine the kinetic parameters of two GEs, StGE2 from the thermophilic fungus Myceliophthora thermophila (syn. Sporotrichum thermophile) and PaGE1 from the coprophilous fungus Podospora anserina. PaGE1 was functionally expressed in the methylotrophic yeast Pichia pastoris under the transcriptional control of the alcohol oxidase (AOX1) promoter and purified to its homogeneity (63 kDa). The three d-glucuronate esters contain an aromatic UV-absorbing phenol group that facilitates the quantification of their enzymatic hydrolysis by HPLC. Both enzymes were able to hydrolyze the synthetic esters with a pronounced preference towards the cinnamyl-d-glucuronate ester. The experimental results were corroborated by computational docking of the synthesized substrate analogues. We show that the nature of the alcohol portion of the hydrolyzed ester influences the catalytic efficiency of the two GEs.

  • 171.
    Katsimpouras, Constantinos
    et al.
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Antonopoulou, Io
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Topakas, Evangelos
    National Technical University of Athens, School of Chemical Engineering, National Technical University of Athens, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Role and Applications of Feruloyl Esterases in Biomass Bioconversion2016Inngår i: Microbial Enzymes in Bioconversions of Biomass / [ed] Vijai Kumar Gupta, Springer international , 2016, s. 79-123Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    Ferulic acid esterases (FAEs) act synergistically with xylanases to hydrolyze the feruloylated decorations of the hemicellulosic fraction of cell wall material and therefore play a major role in the degradation of plant biomass. In this review, their role in plant biomass degradation, their production, classification, and structural determination are discussed. In addition, the production, physicochemical properties, and molecular biology of the different type of FAEs are presented, giving emphasis in their potential applications utilizing their hydrolytic and synthetic activity. A detailed map of the reaction systems used to date is demonstrated, underpinning the potential of these enzymes as biosynthetic tools in the synthesis of bioactive compounds for use in food and cosmeceutical industries.

  • 172.
    Katsimpouras, Constantinos
    et al.
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Topakas, Evangelos
    National Technical University of Athens, School of Chemical Engineering, National Technical University of Athens, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Acetic acid-catalyzed hydrothermal pretreatment of corn stover for the production of bioethanol at high-solids content2016Inngår i: Bioprocess and biosystems engineering (Print), ISSN 1615-7591, E-ISSN 1615-7605, Vol. 39, nr 9, s. 1415-1423Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Corn stover (CS) was hydrothermally pretreated using CH3COOH (0.3 %, v/v), and subsequently its ability to be utilized for conversion to ethanol at high-solids content was investigated. Pretreatment conditions were optimized employing a response surface methodology (RSM) with temperature and duration as independent variables. Pretreated CS underwent a liquefaction/saccharification step at a custom designed free-fall mixer at 50 °C for either 12 or 24 h using an enzyme loading of 9 mg/g dry matter (DM) at 24 % (w/w) DM. Simultaneous enzymatic saccharification and fermentation (SSF) of liquefacted corn stover resulted in high ethanol concentration (up to 36.8 g/L), with liquefaction duration having a negligible effect. The threshold of ethanol concentration of 4 % (w/w), which is required to reduce the cost of ethanol distillation, was surpassed by the addition of extra enzymes at the start up of SSF achieving this way ethanol titer of 41.5 g/L.

  • 173.
    Katsimpouras, Constantinos
    et al.
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Topakas, Evangelos
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Fermentation and Enzymes2014Inngår i: Food engineering handbook: Food process engineering, Boca Raton, Fla.: CRC Press, Taylor & Francis Group , 2014, s. 489-511Kapittel i bok, del av antologi (Fagfellevurdert)
  • 174.
    Katsimpouras, Constantinos
    et al.
    Industrial Biotechnology & Biocatalysis Group, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Dedes, Grigorios
    Industrial Biotechnology & Biocatalysis Group, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Bistis, Perrakis
    Industrial Biotechnology & Biocatalysis Group, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Kekos, Dimitrios
    Industrial Biotechnology & Biocatalysis Group, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Kalogiannis, Konstantinos G.
    Chemical Process and Energy Resources Institute (CPERI) .
    Topakas, Evangelos
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Industrial Biotechnology & Biocatalysis Group, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Acetone/water oxidation of corn stover for the production of bioethanol and prebiotic oligosaccharides2018Inngår i: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 270, s. 208-215Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ethanol production at high-gravity promise to achieve concentrations over the threshold for an economical distillation process and concurrently reduce water consumption. However, a persisting limitation is the poor mass transfer conditions resulting in low ethanol yields and concentrations. Hereby, the combination of an acetone/water oxidation pretreatment process (AWO) with a liquefaction/saccharification step, using a free-fall mixer, before simultaneous saccharification and fermentation (SSF) can realize ethanol concentrations of up to ca. 74 g/L at a solids content of 20 wt.%. The free-fall mixer achieved a biomass slurry’s viscosity reduction by 87 % after only 2 h of enzymatic saccharification, indicating the efficiency of the mixing system. Furthermore, the direct enzymatic treatment of AWO pretreated corn stover (CS) by a GH11 recombinant xylanase, led to the production of xylooligosaccharides (XOS) with prebiotic potential and the removal of insoluble fibers of hemicellulose improved the glucose release of AWOCS by 22 %.

  • 175.
    Katsimpouras, Constantinos
    et al.
    Industrial Biotechnology & Biocatalysis Group, School of Chemical Engineering, National Technical University of Athens, 9 Iroon Polytechniou Str., Zografou Campus, Athens, Greece.
    Dedes, Grigorios
    Industrial Biotechnology & Biocatalysis Group, School of Chemical Engineering, National Technical University of Athens, 9 Iroon Polytechniou Str., Zografou Campus, Athens, Greece.
    Thomaidis, Nikolaos S.
    Laboratory of Analytical Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimioupolis Zografou, Athens, Greece.
    Topakas, Evangelos
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Industrial Biotechnology & Biocatalysis Group, School of Chemical Engineering, National Technical University of Athens, 9 Iroon Polytechniou Str., Zografou Campus, Athens, Greece.
    A novel fungal GH30 xylanase with xylobiohydrolase auxiliary activity2019Inngår i: Biotechnology for Biofuels, ISSN 1754-6834, E-ISSN 1754-6834, Vol. 12, artikkel-id 120Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background:

    The main representatives of hemicellulose are xylans, usually decorated β-1,4-linked d-xylose polymers, which are hydrolyzed by xylanases. The efficient utilization and complete hydrolysis of xylans necessitate the understanding of the mode of action of xylan degrading enzymes. The glycoside hydrolase family 30 (GH30) xylanases comprise a less studied group of such enzymes, and differences regarding the substrate recognition have been reported between fungal and bacterial GH30 xylanases. Besides their role in the utilization of lignocellulosic biomass for bioenergy, such enzymes could be used for the tailored production of prebiotic xylooligosaccharides (XOS) due to their substrate specificity.

    Results:

    The expression of a putative GH30_7 xylanase from the fungus Thermothelomyces thermophila (synonyms Myceliophthora thermophila, Sporotrichum thermophile) in Pichia pastoris resulted in the production and isolation of a novel xylanase with unique catalytic properties. The novel enzyme designated TtXyn30A, exhibited an endo- mode of action similar to that of bacterial GH30 xylanases that require 4-O-methyl-d-glucuronic acid (MeGlcA) decorations, in contrast to most characterized fungal ones. However, TtXyn30A also exhibited an exo-acting catalytic behavior by releasing the disaccharide xylobiose from the non-reducing end of XOS. The hydrolysis products from beechwood glucuronoxylan were MeGlcA substituted XOS, and xylobiose. The major uronic XOS (UXOS) were the aldotriuronic and aldotetrauronic acid after longer incubation indicating the ability of TtXyn30A to cleave linear parts of xylan and UXOS as well.

    Conclusions:

    Hereby, we reported the heterologous production and biochemical characterization of a novel fungal GH30 xylanase exhibiting endo- and exo-xylanase activity. To date, considering its novel catalytic properties, TtXyn30A shows differences with most characterized fungal and bacterial GH30 xylanases. The discovered xylobiohydrolase mode of action offers new insights into fungal enzymatic systems that are employed for the utilization of lignocellulosic biomass. The recombinant xylanase could be used for the production of X2 and UXOS from glucuronoxylan, which in turn would be utilized as prebiotics carrying manifold health benefits.

  • 176.
    Katsimpouras, Constantinos
    et al.
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Dimarogona, Maria
    National Technical University of Athens, Institute of Organic and Pharmaceutical Chemistry, National Hellenic Research Foundation, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Petropoulos, Pericles
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Topakas, Evangelos
    National Technical University of Athens, School of Chemical Engineering, National Technical University of Athens, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    A thermostable GH26 endo-β-mannanase from Myceliophthora thermophila capable of enhancing lignocellulose degradation2016Inngår i: Applied Microbiology and Biotechnology, ISSN 0175-7598, E-ISSN 1432-0614, Vol. 100, nr 19, s. 8385-8397Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The endomannanase gene em26a from the thermophilic fungus Myceliophthora thermophila, belonging to the glycoside hydrolase family 26, was functionally expressed in the methylotrophic yeast Pichia pastoris. The putative endomannanase, dubbed MtMan26A, was purified to homogeneity (60 kDa) and subsequently characterized. The optimum pH and temperature for the enzymatic activity of MtMan26A were 6.0 and 60 °C, respectively. MtMan26A showed high specific activity against konjac glucomannan and carob galactomannan, while it also exhibited high thermal stability with a half-life of 14.4 h at 60 °C. Thermostability is of great importance, especially in industrial processes where harsh conditions are employed. With the aim of better understanding its structure–function relationships, a homology model of MtMan26A was constructed, based on the crystallographic structure of a close homologue. Finally, the addition of MtMan26A as a supplement to the commercial enzyme mixture Celluclast® 1.5 L and Novozyme® 188 resulted in enhanced enzymatic hydrolysis of pretreated beechwood sawdust, improving the release of total reducing sugars and glucose by 13 and 12 %, respectively.

  • 177.
    Katsimpouras, Constantinos
    et al.
    Industrial Biotechnology & Biocatalysis Group, School of Chemical Engineering, National Technical University of Athens.
    Zacharopoulou, Maria
    Industrial Biotechnology & Biocatalysis Group, School of Chemical Engineering, National Technical University of Athens.
    Matsakas, Leonidas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Topakas, Evangelos
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Industrial Biotechnology & Biocatalysis Group, School of Chemical Engineering, National Technical University of Athens.
    Sequential high gravity ethanol fermentation and anaerobic digestion of steam explosion and organosolv pretreated corn stover2017Inngår i: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 244:1, s. 1129-1136Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The present work investigates the suitability of pretreated corn stover (CS) to serve as feedstock for high gravity (HG) ethanol production at solids-content of 24 wt%. Steam explosion, with and without the addition of H2SO4, and organosolv pretreated CS samples underwent a liquefaction/saccharification step followed by simultaneous saccharification and fermentation (SSF). Maximum ethanol concentration of ca. 76 g/L (78.3% ethanol yield) was obtained from steam exploded CS (SECS) with 0.2% H2SO4. Organosolv pretreated CS (OCS) also resulted in high ethanol concentration of ca. 65 g/L (62.3% ethanol yield). Moreover, methane production through anaerobic digestion (AD) was conducted from fermentation residues and resulted in maximum methane yields of ca. 120 and 69 mL/g volatile solids (VS) for SECS and OCS samples, respectively. The results indicated that the implementation of a liquefaction/saccharification step before SSF employing a liquefaction reactor seemed to handle HG conditions adequately.

  • 178.
    Kenny, Diarmuid T.
    et al.
    School of Chemistry and Medical Biochemistry, National University Ireland Galway.
    Gaunitz, Stefan
    Division of Clinical Immunology and Transfusion Medicine, Karolinska Institute.
    Hayes, Catherine A.
    Medical Biochemistry, University of Gothenburg.
    Gustafsson, Anki
    Recopharma AB, Stockholm.
    Sjöblom, Magnus
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Holgersson, Jan
    Absorber AB, Stockholm.
    Karlsson, Niclas G.
    Medical Biochemistry, University of Gothenburg.
    Mass Spectrometric Analysis of O-Linked Oligosaccharides from Various Recombinant Expression Systems2013Inngår i: Glycosylation Engineering of Biopharmaceuticals: Methods and Protocols, New York: Humana Press, 2013, s. 145-167Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    Analysis of O-linked glycosylation is one of the main challenges during structural validation of recombinant glycoproteins. With methods available for N-linked glycosylation in regard to oligosaccharide analysis as well as glycopeptide mapping, there are still challenges for O-linked glycan analysis. Here, we present mass spectrometric methodology for O-linked oligosaccharides released by reductive β-elimination. Using LC-MS and LC-MS2 with graphitized carbon columns, oligosaccharides are analyzed without derivatization. This approach provides a high-throughput method for screening during clonal selection, as well as product structure verification, without impairing sequencing ability. The protocols are exemplified by analysis of glycoproteins from mammalian cell cultures (CHO cells) as well as insect cells and yeast. The data shows that the method can be successfully applied to both neutral and acidic O-linked oligosaccharides, where sialic acid, hexuronic acid, and sulfate are common substituents. Further characterization of O-glycans can be achieved using permethylation. Permethylation of O-linked oligosaccharides followed by direct infusion into the mass spectrometer provide information about oligosaccharide composition, and subsequent MSn experiments can be carried out to elucidate oligosaccharide structure including linkage information and sequence.

  • 179.
    Kirtania, Kawnish
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Axelsson, Joel
    Luleå University of Technology.
    Matsakas, Leonidas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Furusjö, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Umeki, Kentaro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Alkali catalyzed gasification of solid biomass: influence on fuel conversion and tar/soot reduction2016Inngår i: Proceedings of the 24th European Biomass Conference and Exhibition, Amsterdam: ETA Florence Renewable Energies , 2016, s. 533-536Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Based on char gasification experiments in an isothermal thermogravimetric analyzer, a suitable concentration of alkali salt (K2CO3) was chosen for impregnation due to almost five-fold increase in gasification reactivity and relatively low amount of carbon leaching during impregnation. Furthermore, an optimum method for wet alkali impregnation was proposed based on the several tests performed by varying temperature and time. To study the catalytic effect on tar and soot yield, untreated and impregnated woody biomass were gasified under entrained flow condition between 900 oC and 1200 oC. Impregnation leads to 70% lower tar yield from gasification around 1000 oC and 1100 oC. The lowest amount of soot was detected for the same temperature range whereas the soot yield was one order of magnitude higher for untreated biomass. For tar, this influence became insignificant at a higher temperature (1200 oC). This defines the suitable temperature range for alkali catalyzed gasification without the loss of catalytic activity.

  • 180.
    Kosawang, Chatchai
    et al.
    Umeå university.
    Kudahettige-Nilsson, Rasika
    Resman, Lars
    Umeå university.
    Sellstedt, Anita
    Umeå university.
    Hydrogen yield from a hydrogenase in Frankia R43 at different levels of the carbon source propionate2012Inngår i: Journal of Environmental Management, ISSN 0301-4797, E-ISSN 1095-8630, s. 365-368Artikkel i tidsskrift (Fagfellevurdert)
  • 181.
    Krige, Adolf
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Microbial Fuel cells, applications and biofilm characterization2019Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Since the 1900’s it has been known that microorganisms are capable of generating electrical power through extracellular electron transfer by converting the energy found organic compounds (Potter, 1911). Microbial fuel cells (MFCs) has garnered more attention recently, and have shown promise in several applications, including wastewater treatment (Yakar et al., 2018), bioremediation (Rosenbaum & Franks, 2014), biosensors (ElMekawy et al., 2018) desalination (Zhang et al., 2018) and as an alternative renewable energy source in remote areas (Castro et al., 2014). In MFCs catalytic reactions of microorganisms oxidize an electron donor through extracellular electron transfer to the anode, under anaerobic conditions, with the cathode exposed to an electron acceptor, facilitating an electrical current (Zhuwei, Haoran & Tingyue, 2007; Lovley, 2006). For energy production in remote areas a low cost and easily accessible feed stock is required for the MFCs. Sweet sorghum is a drought tolerant feedstock with high biomass and sugar yields, good water-use efficiency, established production systems and the potential for genetic improvements. Because of these advantages sweet sorghum stalks were proposed as an attractive feedstock (Rooney et al., 2010; Matsakas & Christakopoulos, 2013). Dried sweet sorghum stalks were, therefore, tested as a raw material for power generation in a MFC, with anaerobic sludge from a biogas plant as inoculum (Sjöblom et al., 2017a).

    Using sorghum stalks the maximum voltage obtained was 546±10 mV, the maximum power and current density of 131±8 mW/m2 and 543±29 mA/m2 respectively and the coulombic efficiency was 2.2±0.5%. The Ohmic resistances were dominant, at an internal resistance of 182±17 Ω, calculated from polarization data. Furthermore, hydrolysis of the dried sorghum stalks did not improve the performance of the MFC but slightly increased the total energy per gram of substrate. During the MFC operation, the sugars were quickly fermented to formate, acetate, butyrate, lactate and propionate with acetate and butyrate being the key acids during electricity generation.

    Efficient electron transfer between the microorganisms and the electrodes is an essential aspect of bio-electrochemical systems such as microbial fuel cells. In order to design more efficient reactors and to modify microorganisms, for enhanced electricity production, understanding the mechanisms and dynamics of the electron transport chain is important. It has been found that outer membrane C-type cytochromes (OMCs) (including omcS and omcZ discussed in this study) play a key role in the electron transport chain of Geobacter sulfurreducens, a well-known, biofilm forming, electro-active microorganism  (Millo et al., 2011; Lovley, 2008). It was found that Raman microscopy is capable of providing biochemical information, i.e., the redox state of c-type cytochromes (cyt-C) without damaging the microbial biofilm, allowing for in-situ observation.

    Raman microscopy was used to observe the oxidation state of OMCs in a suspended culture, as well as in a biofilm of an MFC. First, the oxidation state of the OMCs of suspended cultures from three G. sulfurreducens strains (PCA, KN400 and ΔpilA) was analyzed. It was found that the oxidation state can also be used as an indicator of the metabolic state of the cells, and it was confirmed that PilA, a structural pilin protein essential for long range electron transfer, is not required for external electron transfer. Furthermore, we designed a continuous, anaerobic MFC enabling in-situ Raman measurements of G. sulfurreducens biofilms during electricity generation, while poised using a potentiostat, in order to monitor and characterize the biofilm. Two strains were used, a wild strain, PCA, and a mutant, ΔOmcS. The cytochrome redox state, observed through the Raman spectra, could be altered by applying different poise voltages to the electrodes. This change was indirectly proportional to the modulation of current transferred from the cytochromes to the electrode. This change in Raman peak area was reproducible and reversible, indicating that the system could be used, in-situ, to analyze the oxidation state of proteins responsible for the electron transfer process and the kinetics thereof.

  • 182.
    Krige, Adolf
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Sjöblom, Magnus
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Ramser, Kerstin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    On-line Raman spectroscopic study of cytochromes’ redox state of biofilms in microbial fuel cells2019Inngår i: Molecules, ISSN 1420-3049, E-ISSN 1420-3049, Vol. 24, nr 3, artikkel-id 646Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Bio-electrochemical systems such as microbial fuel cells and microbial electrosynthesis cells depend on efficient electron transfer between the microorganisms and the electrodes. Understanding the mechanisms and dynamics of the electron transfer is important in order to design more efficient reactors, as well as modifying microorganisms for enhanced electricity production. Geobacter are well known for their ability to form thick biofilms and transfer electrons to the surfaces of electrodes. Currently, there are not many “on-line” systems for monitoring the activity of the biofilm and the electron transfer process without harming the biofilm. Raman microscopy was shown to be capable of providing biochemical information, i.e., the redox state of C-type cytochromes, which is integral to external electron transfer, without harming the biofilm. In the current study, a custom 3D printed flow-through cuvette was used in order to analyze the oxidation state of the C-type cytochromes of suspended cultures of three Geobacter sulfurreducens strains (PCA, KN400 and ∆pilA). It was found that the oxidation state is a good indicator of the metabolic state of the cells. Furthermore, an anaerobic fluidic system enabling in situ Raman measurements was designed and applied successfully to monitor and characterize G. sulfurreducens biofilms during electricity generation, for both a wild strain, PCA, and a mutant, ∆S. The cytochrome redox state, monitored by the Raman peak areas, could be modulated by applying different poise voltages to the electrodes. This also correlated with the modulation of current transferred from the cytochromes to the electrode. The Raman peak area changed in a predictable and reversible manner, indicating that the system could be used for analyzing the oxidation state of the proteins responsible for the electron transfer process and the kinetics thereof in-situ. 

  • 183.
    Kroll, Jens
    et al.
    Westfälische Wilhelms-Universität Münster, Germany.
    Klinter, Stefan
    Westfälische Wilhelms-Universität Münster, Germany.
    Steinbüchel, Alexander
    Westfälische Wilhelms-Universität Münster, Germany.
    A novel plasmid addiction system for large-scale production of cyanophycin in Escherichia coli using mineral salts medium2011Inngår i: Applied Microbiology and Biotechnology, ISSN 0175-7598, E-ISSN 1432-0614, Vol. 89, nr 3, s. 593-604Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Introduction: Hitherto the production of the biopolymer cyanophycin (CGP) using recombinant Escherichia coli strains and cheap mineral salts medium yielded only trace amounts of CGP (<0.5%, w/w) of the cell dry matter (CDM). This was probably due to the instability of the plasmids encoding the cyanophycin synthetase. Material and methods: In this study, we developed an anabolism-based media-dependent plasmid addiction system (PAS) to enhance plasmid stability, and we established a process based on a modified mineral salts medium yielding a CGP content of 42% (w/w) at the maximum without the addition of amino acids to the medium for the first time. This PAS is based on different lysine biosynthesis pathways and consists of two components: (1) a knockout of the chromosomal dapE disrupts the native succinylase pathway in E. coli and (2) the complementation by the plasmid-encoded artificial aminotransferase pathway mediated by the dapL gene from Synechocystis sp. PCC 6308, which allows the synthesis of the essential lysine precursor L,L-2,6-diaminopimelate. In addition, this plasmid also harbors cphAC595S, an engineered cyanophycin synthetase gene responsible for CGP production. Results: Cultivation experiments in Erlenmeyer flask and also in bioreactors in mineral salts medium without antibiotics revealed an at least 4.5-fold enhanced production of CGP in comparison to control cultivations without PAS. Discussion: Fermentation experiments with culture volume of up to 400 l yielded a maximum of 18% CGP (w/w) and a final cell density of 15.2 g CDM/l. Lactose was used constantly as an effective inducer and carbon source. Thus, we present a convenient option to produce CGP with E. coli at a technical scale without the need to add antibiotics or amino acids using the mineral salts medium designed in this study.

  • 184.
    Kudahettige-Nilsson, Rasika
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Helmerius, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Nilsson, Robert
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Sjöblom, Magnus
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Hodge, David
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Biobutanol Production by Clostridium acetobutylicum Using Xylose Recovered from Birch Kraft Black Liquor2015Inngår i: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 176, s. 71-79Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Acetone-Butanol-Ethanol (ABE) fermentation was studied using acid-hydrolyzed xylan recovered from hardwood Kraft black liquor by CO2 acidification as the only carbon source. Detoxification of hydrolyzate using activated carbon was conducted to evaluate the impact of inhibitor removal and fermentation. Xylose hydrolysis yields as high as 18.4% were demonstrated at the highest severity hydrolysis condition. Detoxification using active carbon was effective for removal of both phenolics (76-81%) and HMF (38-52%). Batch fermentation of the hydrolyzate and semi-defined P2 media resulted in a total solvent yield of 0.12-0.13 g/g and 0.34 g/g, corresponding to a butanol concentration of 1.8-2.1 g/L and 7.3 g/L respectively. This work is the first study of a process for the production of a biologically-derived biofuel from hemicelluloses solubilized during Kraft pulping and demonstrates the feasibility of utilizing xylan recovered directly from industrial Kraft pulping liquors as a feedstock for biological production of biofuels such as butanol.

  • 185. Kudahettige-Nilsson, Rasika
    et al.
    Holmgren, Marie
    Umeå university.
    Imerzeel, Peter
    Umeå university.
    Sellstedt, Anita
    Umeå university.
    Characterization of bioethanol production from hexoses and xylose by the white rot fungus Trametes versicolor2012Inngår i: Bioenergy Research, ISSN 1939-1234, E-ISSN 1939-1242, s. 277-285Artikkel i tidsskrift (Fagfellevurdert)
  • 186. Kudahettige-Nilsson, Rasika
    et al.
    Holmgren, Marie
    Umeå Plant Science Centre, Department of Plant Physiology, Umeå University.
    Madavi, Batol
    Tarbiat Modares University.
    Nilsson, Robert
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Sellstedt, Anita
    Umeå Plant Science Centre, Department of Plant Physiology, Umeå University.
    Adaptability of Trametes versicolor to the lignocellulosic inhibitors furfural, HMF, phenol and levulinic acid during ethanol fermentation2016Inngår i: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 90, s. 95-100Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ligno-cellulosic biofuels, notably ethanol produced in processes involving biological fermentation, have high potential as renewable alternatives to fossil fuels. However, ligno-cellulose pretreatment procedures generate substances that inhibit current biocatalysts. Thus, efficient methods are required for improving these organisms' tolerance or developing new biocatalysts with higher tolerance to the inhibitors. For this, greater knowledge of the mechanisms involved is needed. Therefore, we examined effects of common inhibitors (phenol, levulinic acid, HMF (hydroxymethylfurfural) and furfural) on growth, utilization of sugars (xylose, mannose and glucose) and enzyme activities of a tolerant organism, the white-rot fungus Trametes versicolor, during 15-day incubations. The fungus metabolized and grew in the presence of all the inhibitors (singly and together) at the applied concentration (0.2–0.6 g/L). When all inhibitors were added, no significant effect of sugar utilization was shown. However, levulinic acid added solely reduced xylose (but not xylose-degrading enzymes) and mannose utilization, but not glucose utilization. Physiological and biotechnological implications of the findings are discussed such as usage of T. versicolor as a detoxifying agent in ethanol production.

  • 187.
    Lage, Sandra
    et al.
    Swedish University of Agricultural Sciences, Umeå.
    Kudahettige, Nirupa P.
    Swedish University of Agricultural Sciences, Umeå.
    Ferro, Lorenza
    Umeå University, Umeå.
    Matsakas, Leonidas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Funk, Christiane
    Umeå University, Umeå.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Gentili, Francesco G.
    Swedish University of Agricultural Sciences, Umeå.
    Microalgae Cultivation for the Biotransformation of Birch Wood Hydrolysate and Dairy Effluent2019Inngår i: Catalysts, ISSN 2073-4344, Vol. 9, nr 2, artikkel-id 150Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In order to investigate environmentally sustainable sources of organic carbon and nutrients, four Nordic green microalgal strains, Chlorella sorokiniana, Chlorella saccharophila, Chlorella vulgaris, and Coelastrella sp., were grown on a wood (Silver birch, Betula pendula) hydrolysate and dairy effluent mixture. The biomass and lipid production were analysed under mixotrophic, as well as two-stage mixotrophic/heterotrophic regimes. Of all of the species, Coelastrella sp. produced the most total lipids per dry weight (~40%) in the mixture of birch hydrolysate and dairy effluent without requiring nutrient (nitrogen, phosphorus, and potassium-NPK) supplementation. Overall, in the absence of NPK, the two-stage mixotrophic/heterotrophic cultivation enhanced the lipid concentration, but reduced the amount of biomass. Culturing microalgae in integrated waste streams under mixotrophic growth regimes is a promising approach for sustainable biofuel production, especially in regions with large seasonal variation in daylight, like northern Sweden. To the best of our knowledge, this is the first report of using a mixture of wood hydrolysate and dairy effluent for the growth and lipid production of microalgae in the literature.

  • 188.
    Larson, M.A.
    et al.
    Iowa State University.
    White, E.T.
    Iowa State University.
    Ramanarayanan, K. A.
    Iowa State University.
    Berglund, Kris
    Growth rate dispersion in MSMPR crystallizers1985Inngår i: AIChE Journal, ISSN 0001-1541, E-ISSN 1547-5905, Vol. 31, nr 1, s. 90-94Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A model is presented which relates the crystal size distribution (CSD) from a mixed-suspension, mixed-product-removal (MSMPR) crystallizer to the distribution of growth rates. This model is based on the assumption that individual contact nuclei have some inherent growth rate which remains constant, but the growth rate may vary from crystal to crystal. The crystal size distribution can be calculated from prior knowledge of the growth rate distribution. A limited knowledge of only the coefficient of variation and the mean growth rate permits an approximation of the expected crystal size distribution. Conversely, estimates of the mean and variance of the growth rate distribution can be determined from the moments of the CSD from an MSMPR crystallizer

  • 189.
    LeCaptain, D.J.
    et al.
    Michigan State University.
    Berglund, Kris
    Applicability of second harmonic generation for in situ measurement of induction time of selected crystallization systems1999Inngår i: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 203, nr 4, s. 564-569Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The nonlinear optical technique of second harmonic generation (SHG) is introduced as a novel technique for monitoring particle formation in batch crystallizations. SHG is more sensitive and is less prone to interference than turbidometric methods. The studies presented show the applicability of SHG as a method for in situ measuring the induction time of a number of noncentrosymmetric crystal systems.

  • 190.
    Li, Muyang
    et al.
    DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, Michigan State University, Department of Biosystems & Agricultural Engineering, Michigan State University, East Lansing.
    Heckwolf, Marlies
    DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Crowe, Jacob D.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Williams, Daniel L.
    Michigan State University, DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Magee, Timothy D.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Kaeppler, Shawn M.
    DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Lion, Natalia de
    DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Hodge, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Cell-wall properties contributing to improved deconstruction by alkaline pre-treatment and enzymatic hydrolysis in diverse maize (Zea mays L.) lines2015Inngår i: Journal of Experimental Botany, ISSN 0022-0957, E-ISSN 1460-2431, Vol. 66, nr 14, s. 4305-4315Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A maize (Zea mays L. subsp. mays) diversity panel consisting of 26 maize lines exhibiting a wide range of cell-wall properties and responses to hydrolysis by cellulolytic enzymes was employed to investigate the relationship between cell-wall properties, cell-wall responses to mild NaOH pre-treatment, and enzymatic hydrolysis yields. Enzymatic hydrolysis of the cellulose in the untreated maize was found to be positively correlated with the water retention value, which is a measure of cell-wall susceptibility to swelling. It was also positively correlated with the lignin syringyl/guaiacyl ratio and negatively correlated with the initial cell-wall lignin, xylan, acetate, and p-coumaric acid (pCA) content, as well as pCA released from the cell wall by pre-treatment. The hydrolysis yield following pre-treatment exhibited statistically significant negative correlations to the lignin content after pre-treatment and positive correlations to the solubilized ferulic acid and pCA. Several unanticipated results were observed, including a positive correlation between initial lignin and acetate content, lack of correlation between acetate content and initial xylan content, and negative correlation between each of these three variables to the hydrolysis yields for untreated maize. Another surprising result was that pCA release was negatively correlated with hydrolysis yields for untreated maize and, along with ferulic acid release, was positively correlated with the pre-treated maize hydrolysis yields. This indicates that these properties that may negatively contribute to the recalcitrance in untreated cell walls may positively contribute to their deconstruction by alkaline pre-treatment.

  • 191.
    Li, Muyang
    et al.
    Michigan State University.
    Pattathil, Sivakumar
    University of Georgia.
    Hahn, Michael G
    University of Georgia.
    Hodge, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Identification of features associated with plant cell wall recalcitrance to pretreatment by alkaline hydrogen peroxide in diverse bioenergy feedstocks using glycome profiling2014Inngår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 4, nr 33, s. 17282-17292Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A woody dicot (hybrid poplar), an herbaceous dicot (goldenrod), and a graminaceous monocot (corn stover) were subjected to alkaline hydrogen peroxide (AHP) pretreatment and subsequent enzymatic hydrolysis in order to assess how taxonomically and structurally diverse biomass feedstocks respond to a mild alkaline oxidative pretreatment and how differing features of the cell wall matrix contribute to its recalcitrance. Using glycome profiling, we determined changes in the extractability of non-cellulosic glucans following pretreatment by screening extracts of the pretreated walls with a panel of 155 cell wall glycan-directed monoclonal antibodies to determine differences in the abundance and distribution of non-cellulosic glycan epitopes in these extracts and assess pretreatment-induced changes in the structural integrity of the cell wall. Two taxonomically-dependent outcomes of pretreatment were identified that both improved the subsequent enzymatic hydrolysis yields but differed in their impacts on cell wall structural integrity. Specifically, it was revealed that goldenrod walls exhibited decreases in all classes of alkali-extractable glycans indicating their solubilization during pretreatment, which was accompanied by an improvement in the subsequent extractability of the remaining cell wall glycans. The corn stover walls did not show the same decreases in glycan abundance in extracts following pretreatment, but rather mild increases in all classes of cell wall glycans, indicating overall weaker associations between cell wall polymers and improved extractability. The hybrid poplar walls were relatively unaffected by pretreatment in terms of composition, enzymatic hydrolysis, and the extractability of cell wall glycans due presumably to their higher lignin content and denser vascular structure.

  • 192.
    Li, Muyang
    et al.
    Department of Plant Biology, Michigan State University, East Lansing, .
    Williams, Daniel L.
    DOE Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, .
    Heckwolf, Marlies
    Department of Agronomy, University of Wisconsin, Madison.
    de Leon, Natalia
    Department of Agronomy, University of Wisconsin, Madison.
    Kaeppler, Shawn
    Department of Agronomy, University of Wisconsin, Madison.
    Sykes, Robert W.
    National Renewable Energy Laboratory, Golden.
    Hodge, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Prediction of Cell Wall Properties and Response to Deconstruction Using Alkaline Pretreatment in Diverse Maize Genotypes Using Py-MBMS and NIR2017Inngår i: Bioenergy Research, ISSN 1939-1234, E-ISSN 1939-1242, Vol. 10, nr 2, s. 329-343Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, we explore the ability of several characterization approaches for phenotyping to extract information about plant cell wall properties in diverse maize genotypes with the goal of identifying approaches that could be used to predict the plant’s response to deconstruction in a biomass-to-biofuel process. Specifically, a maize diversity panel was subjected to two high-throughput biomass characterization approaches, pyrolysis molecular beam mass spectrometry (py-MBMS) and near-infrared (NIR) spectroscopy, and chemometric models to predict a number of plant cell wall properties as well as enzymatic hydrolysis yields of glucose following either no pretreatment or with mild alkaline pretreatment. These were compared to multiple linear regression (MLR) models developed from quantified properties. We were able to demonstrate that direct correlations to specific mass spectrometry ions from pyrolysis as well as characteristic regions of the second derivative of the NIR spectrum regions were comparable in their predictive capability to partial least squares (PLS) models for p-coumarate content, while the direct correlation to the spectral data was superior to the PLS for Klason lignin content and guaiacyl monomer release by thioacidolysis as assessed by cross-validation. The PLS models for prediction of hydrolysis yields using either py-MBMS or NIR spectra were superior to MLR models based on quantified properties for unpretreated biomass. However, the PLS models using the two high-throughput characterization approaches could not predict hydrolysis following alkaline pretreatment while MLR models based on quantified properties could. This is likely a consequence of quantified properties including some assessments of pretreated biomass, while the py-MBMS and NIR only utilized untreated biomass.

  • 193.
    Li, Muyang
    et al.
    Department of Biosystems & Agricultural Engineering, Michigan State University, East Lansing .
    Yan, Guilong
    School of Life Science, Huaiyin Normal University, Huaian, Jiangsu.
    Bhalla, Aditya
    DOE Great Lakes Bioenergy Research Center, Michigan State University.
    Maldonado-Pereira, Lisaura
    Department of Biosystems & Agricultural Engineering, Michigan State University, East Lansing .
    Russell, Petria R.
    Department of Chemical & Biological Engineering, Montana State University.
    Ding, Shi-You
    DOE Great Lakes Bioenergy Research Center, Michigan State University.
    Mullet, John E.
    DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Hodge, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Department of Chemical & Biological Engineering, Montana State University, Bozeman, MT.
    Physical fractionation of sweet sorghum and forage/energy sorghum for optimal processing in a biorefinery2018Inngår i: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 124, s. 607-616Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sorghum offers enormous potential as a feedstock for the production of fuels and chemicals from both water-extractable sugars and the cell wall biopolymers, while its within-plant structural and compositional heterogeneity may allow for physical fractionations to tailor feedstock properties to a biorefining process. In this study, the stem internodes of two sorghum (Sorghum bicolor L. Moench) genotypes, a sweet sorghum (‘Della’) and a forage/energy sorghum (‘TX08001’), were first subjected to fractionation by manual classification by stem anatomy and internode proximity to the ground to yield 18 fractions. These fractions exhibited substantial differences in cell wall morphology, composition, and recalcitrance to mild alkaline pretreatment and enzymatic hydrolysis. While the sweet sorghum cultivar held nearly 70% more water-extractable sugar (sucrose, glucose, fructose, starch) in the stems than the forage/energy sorghum hybrid, both cultivars exhibited comparable diversity of composition and these compositions were remarkably similar in similar tissues and stem regions between the two cultivars. The fractions isolated from the pith parenchyma were the least recalcitrant to mild alkaline pretreatment and enzymatic hydrolysis and contained less lignin than fractions isolated from the epidermis, outer and inner rind, and internal vascular bundles. The pith samples isolated from the lowest region of the stem from both cultivars exhibited near-theoretical sugar hydrolysis yields when no pretreatment was employed and exhibited the lowest lignin contents of any of the fractions. Next, a physical fractionation approach approximating a commercial “de-pithing” process utilizing wet disintegration and sieving was applied to the forage/energy sorghum. A pith-rich fraction representing approximately 20% of the extractives-free mass of the stem could be isolated with this approach and, relative to the other fractions, was low in lignin, high in ash, highly hygroscopic, and showed an improved response to mild alkaline pretreatment and enzymatic hydrolysis at low enzyme loadings. Overall, these results demonstrate how heterogeneity within sorghum stems can be exploited using physical fractionation approaches to yield fractions enriched in desired properties that may allow for more streamlined processing.

  • 194.
    Li, Zhenglun
    et al.
    Michigan State University, Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Bansal, Namita
    DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Azarpira, Ali
    DOE-Great Lakes Bioenergy Research Center, University of Wisconsin, Madison.
    Bhalla, Aditya
    DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Chen, Charles H.
    Michigan State University, Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Ralph, John P.
    DOE-Great Lakes Bioenergy Research Center, University of Wisconsin, Madison.
    Hegg, Eric L.
    Michigan State University, DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Hodge, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Chemical and structural changes associated with Cu-catalyzed alkaline-oxidative delignification of hybrid poplar2015Inngår i: Biotechnology for Biofuels, ISSN 1754-6834, E-ISSN 1754-6834, Vol. 8, nr 1, artikkel-id 123Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: Alkaline hydrogen peroxide pretreatment catalyzed by Cu(II) 2,2′-bipyridine complexes has previously been determined to substantially improve the enzymatic hydrolysis of woody plants including hybrid poplar as a consequence of moderate delignification. In the present work, cell wall morphological and lignin structural changes were characterized for this pretreatment approach to gain insights into pretreatment outcomes and, specifically, to identify the extent and nature of lignin modification. Results: Through TEM imaging, this catalytic oxidation process was shown to disrupt cell wall layers in hybrid poplar. Cu-containing nanoparticles, primarily in the Cu(I) oxidation state, co-localized with the disrupted regions, providing indirect evidence of catalytic activity whereby soluble Cu(II) complexes are reduced and precipitated during pretreatment. The concentration of alkali-soluble polymeric and oligomeric lignin was substantially higher for the Cu-catalyzed oxidative pretreatment. This alkali-soluble lignin content increased with time during the catalytic oxidation process, although the molecular weight distributions were unaltered. Yields of aromatic monomers (including phenolic acids and aldehydes) were found to be less than 0.2 % (wt/wt) on lignin. Oxidation of the benzylic alcohol in the lignin side-chain was evident in NMR spectra of the solubilized lignin, whereas minimal changes were observed for the pretreatment-insoluble lignin. Conclusions: These results provide indirect evidence for catalytic activity within the cell wall. The low yields of lignin-derived aromatic monomers, together with the detailed characterization of the pretreatment-soluble and pretreatment-insoluble lignins, indicate that the majority of both lignin pools remained relatively unmodified. As such, the lignins resulting from this process retain features closely resembling native lignins and may, therefore, be amenable to subsequent valorization.

  • 195.
    Li, Zhenglun
    et al.
    Michigan State University.
    Chen, Charles H.
    Michigan State University.
    Liu, Tongjun
    Michigan State University.
    Mathrubootham, Vaidyanathan
    Michigan State University.
    Hegg, Eric L.
    Michigan State University.
    Hodge, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Catalysis with Cuii(bpy) improves alkaline hydrogen peroxide pretreatment2013Inngår i: Biotechnology and Bioengineering, ISSN 0006-3592, E-ISSN 1097-0290, Vol. 110, nr 4, s. 1078-1086Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Copper(II) 2,2′-bipyridine (CuII(bpy))-catalyzed alkaline hydrogen peroxide (AHP) pretreatment was performed on three biomass feedstocks including alkali pre-extracted switchgrass, silver birch, and a hybrid poplar cultivar. This catalytic approach was found to improve the subsequent enzymatic hydrolysis of plant cell wall polysaccharides to monosaccharides for all biomass types at alkaline pH relative to uncatalyzed pretreatment. The hybrid poplar exhibited the most significant improvement in enzymatic hydrolysis with monomeric sugar release and conversions more than doubling from 30% to 61% glucan conversion, while lignin solubilization was increased from 36.6% to 50.2% and hemicellulose solubilization was increased from 14.9% to 32.7%. It was found that CuII(bpy)-catalyzed AHP pretreatment of cellulose resulted in significantly more depolymerization than uncatalyzed AHP pretreatment (78.4% vs. 49.4% decrease in estimated degree of polymerization) and that carboxyl content the cellulose was significantly increased as well (fivefold increase vs. twofold increase). Together, these results indicate that CuII(bpy)-catalyzed AHP pretreatment represents a promising route to biomass deconstruction for bioenergy applications

  • 196.
    Liang, B.
    et al.
    University of Wisconsin.
    Hartel, R.W.
    University of Wisconsin.
    Berglund, Kris
    Effects of raffinose on sucrose crystal growth kinetics and rate dispersion1989Inngår i: AIChE Journal, ISSN 0001-1541, E-ISSN 1547-5905, Vol. 35, nr 12, s. 2053-2057Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This work seeks to further the investigation of the effects of raffinose on both the crystallization kinetics and GRD of growing sucrose crystals. Measurements of the widening of the crystal size distribution (CSD) of suspension grown seed crystals, as well as direct photomicroscopic measurements of the growth of these seed crystals, were completed for this study. The range of supersaturation studied was 0.28 to 2.05 g sucrose per 100 g solution with a temperature range of 313 to 333 K. The results of a previous investigation on the solubility of sucrose in raffinose solution were utilized for the kinetic determinations.

  • 197.
    Liang, B. M.
    et al.
    Michigan State University.
    Hartel, R.W.
    Michigan State University.
    Berglund, Kris
    Growth rate dispersion in seeded batch sucrose crystallization1987Inngår i: AIChE Journal, ISSN 0001-1541, E-ISSN 1547-5905, Vol. 33, nr 12, s. 2077-2079Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The object of this study was to compare the results of batch suspension and photomicroscopic cell experiments on growth rate dispersion of sucrose seed crystals to determine the relative effects of GRD in the two different environments. This was done by observing the change in CSD of the seed distribution in the batch suspension crystallizer, while simultaneously monitoring the individual growth rates of an identical seed sample in the photomicroscopic cell. It is found that seeds growing in a stirred suspension batch crystallizer also exhibit growth rate dispersion, as evidenced by the increasing width of the CSD with time.

  • 198.
    Liao, Wei
    et al.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Liu, Yan
    Department of Biosystems & Agricultural Engineering, Michigan State University, East Lansing.
    Hodge, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Integrated Farm-Based Biorefinery2014Inngår i: Biorefineries: Integrated Biochemical Processes for Liquid Biofuels, Amsterdam: Elsevier, 2014, s. 255-270Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    Animal manure and crop residues are agricultural wastes rich in carbohydrates and nitrogen that represent a largely untapped reservoir of biomass. These farm wastes have great potential as feedstocks for the production of renewable biobased energy and chemical products. This chapter presents a novel integrated farm-based biorefining system for producing ethanol, methane, and algal biomass from a mixed feedstock of animal manure and corn stover. The system includes three unit operations for anaerobic digestion (AD), algae cultivation, and bioethanol production. The AD process produces methane and pretreats the biomass fiber for bioethanol production. The algae cultivation process treats the liquid AD effluent, further reducing the environmental impacts of excess nutrients in the agricultural residues and generating a protein-rich algal biomass. Finally, a bioethanol process utilizes the carbohydrates in the AD-treated fiber to produce ethanol. The integrated system uses the advantages of individual biological processes to synergistically improve the energy efficiency of lignocellulosic biofuel production, address the water usage of lignocellulosic biorefining, provide a solution to -problems with feedstock logistics, and alleviate the environmental impacts of agricultural residues. This integrated biological process could eventually lead to reducing our reliance on fossil fuel, while simultaneously maximizing farmers' interests and minimizing environmental impacts

  • 199.
    Lingman, Peter
    et al.
    Optimation AB.
    Eriksson, Tomas
    Optimation AB.
    Marklund, Joacim
    Softronic AB.
    Lindström, Curt
    Luleå University of Technology.
    Nilsson, Robert
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Gamifcation in web based dynamical simulations2016Konferansepaper (Annet vitenskapelig)
  • 200.
    Liu, Bing
    et al.
    Department of Molecular Sciences, Swedish University of Agricultural Sciences, Uppsala.
    Krishnaswamyreddy, Sumitha
    Department of Molecular Sciences, Swedish University of Agricultural Sciences, Uppsala.
    Muraleedharan, Madhu Nair
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Olson, Åke
    Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, Uppsala.
    Broberg, Anders
    Department of Molecular Sciences, Swedish University of Agricultural Sciences, Uppsala.
    Ståhlberg, Jerry
    Department of Molecular Sciences, Swedish University of Agricultural Sciences, Uppsala.
    Sandgren, Mats
    Department of Molecular Sciences, Swedish University of Agricultural Sciences, Uppsala.
    Side-by-side biochemical comparison of two lytic polysaccharide monooxygenases from the white-rot fungus Heterobasidion irregulare on their activity against crystalline cellulose and glucomannan2018Inngår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 13, nr 9, artikkel-id e0203430Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Our comparative studies reveal that the two lytic polysaccharide monooxygenases HiLP-MO9B and HiLPMO9I from the white-rot conifer pathogen Heterobasidion irregulare display clear difference with respect to their activity against crystalline cellulose and glucomannan. HiLPMO9I produced very little soluble sugar on bacterial microcrystalline cellulose (BMCC). In contrast, HiLPMO9B was much more active against BMCC and even released more soluble sugar than the H. irregulare cellobiohydrolase I, HiCel7A. Furthermore, HiLPMO9B was shown to cooperate with and stimulate the activity of HiCel7A, both when the BMCC was first pretreated with HiLPMO9B, as well as when HiLPMO9B and HiCel7A were added together. No such stimulation was shown by HiLPMO9I. On the other hand, HiLPMO9I was shown to degrade glucomannan, using a C4-oxidizing mechanism, whereas no oxidative cleavage activity of glucomannan was detected for HiLPMO9B. Structural modeling and comparison with other glucomannan-active LPMOs suggest that conserved sugar-interacting residues on the L2, L3 and LC loops may be essential for glucomannan binding, where 4 out of 7 residues are shared by HiLPMO9I, but only one is found in HiLPMO9B. The difference shown between these two H. irregulare LPMOs may reflect distinct biological roles of these enzymes within deconstruction of different plant cell wall polysaccharides during fungal colonization of softwood.

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