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  • 151.
    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.

  • 152.
    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.

  • 153.
    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.

  • 154.
    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.

  • 155.
    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.

  • 156.
    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.

  • 157.
    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.

  • 158.
    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.

  • 159.
    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)
  • 160.
    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 %.

  • 161.
    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.

  • 162.
    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.

  • 163.
    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.

  • 164.
    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.

  • 165.
    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)
  • 166.
    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.

  • 167.
    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.

  • 168. 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)
  • 169. 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.

  • 170.
    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

  • 171.
    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.

  • 172.
    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.

  • 173.
    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.

  • 174.
    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.

  • 175.
    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.

  • 176.
    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.

  • 177.
    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

  • 178.
    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.

  • 179.
    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.

  • 180.
    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

  • 181.
    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)
  • 182.
    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.

  • 183.
    Liu, Tongjun
    et al.
    Michigan State University.
    Williams, Daniel L.
    Michigan State University.
    Pattathil, Sivakumar
    University of Georgia.
    Li, Muyang
    Michigan State University.
    Hahn, Michael G
    University of Georgia.
    Hodge, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Coupling alkaline pre-extraction with alkaline-oxidative post-treatment of corn stover to enhance enzymatic hydrolysis and fermentability2014Inngår i: Biotechnology for Biofuels, ISSN 1754-6834, E-ISSN 1754-6834, Vol. 7, artikkel-id 48Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: A two-stage chemical pretreatment of corn stover is investigated comprising an NaOH pre-extraction followed by an alkaline hydrogen peroxide (AHP) post-treatment. We propose that conventional one-stage AHP pretreatment can be improved using alkaline pre-extraction, which requires significantly less H2O2 and NaOH. To better understand the potential of this approach, this study investigates several components of this process including alkaline pre-extraction, alkaline and alkaline-oxidative post-treatment, fermentation, and the composition of alkali extracts.Results: Mild NaOH pre-extraction of corn stover uses less than 0.1 g NaOH per g corn stover at 80 degrees C. The resulting substrates were highly digestible by cellulolytic enzymes at relatively low enzyme loadings and had a strong susceptibility to drying-induced hydrolysis yield losses. Alkaline pre-extraction was highly selective for lignin removal over xylan removal; xylan removal was relatively minimal (similar to 20%). During alkaline pre-extraction, up to 0.10 g of alkali was consumed per g of corn stover. AHP post-treatment at low oxidant loading (25 mg H2O2 per g pre-extracted biomass) increased glucose hydrolysis yields by 5%, which approached near-theoretical yields. ELISA screening of alkali pre-extraction liquors and the AHP post-treatment liquors demonstrated that xyloglucan and beta-glucans likely remained tightly bound in the biomass whereas the majority of the soluble polymeric xylans were glucurono (arabino) xylans and potentially homoxylans. Pectic polysaccharides were depleted in the AHP post-treatment liquor relative to the alkaline pre-extraction liquor. Because the already-low inhibitor content was further decreased in the alkaline pre-extraction, the hydrolysates generated by this two-stage pretreatment were highly fermentable by Saccharomyces cerevisiae strains that were metabolically engineered and evolved for xylose fermentation.Conclusions: This work demonstrates that this two-stage pretreatment process is well suited for converting lignocellulose to fermentable sugars and biofuels, such as ethanol. This approach achieved high enzymatic sugars yields from pretreated corn stover using substantially lower oxidant loadings than have been reported previously in the literature. This pretreatment approach allows for many possible process configurations involving novel alkali recovery approaches and novel uses of alkaline pre-extraction liquors. Further work is required to identify the most economical configuration, including process designs using techno-economic analysis and investigating processing strategies that economize water use.

  • 184.
    Lundgren, Joakim
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Helmerius, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Integration of a hemicellulose extraction process into a biomass based heat and power plant2009Inngår i: Proceedings of ECOS 2009: 22nd International Conference on Efficiency, Cost, Optimization Simulation and Environmental Impact of Energy Systems, Foz do Iguaçú: ABCM, Brazilian Society of Mechanical Sciences and Engineering , 2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The development of processes where lignocellulosic biomass can be refined to several different end-products in the same plant, i.e. a biorefinery, will be important in the development towards a more sustainable society where fossil fuels are replaced. This paper presents the idea to integrate the production of green chemicals via hot water hemicellulose extraction of birch wood (hardwood) into a small-scale combined heat and power plant (CHP), in this case an externally fired gas turbine. A techno-economically successful concept could provide the option to turn a small- to medium scale CHP plant into a small- to medium scale biorefinery. The results show that the extracted wood-chips would serve very well as a fuel for combustion and gasification processes due to the relatively high heating value, low ash content and significantly lower concentrations of alkali metals. Under the assumed economic conditions, electricity can be produced to a cost in the range of €85.6 to €196.2 per MWhel and a fermentable feedstock stream with a xylose concentration of 65 g/L to a cost in between €0.44 to €4.15 per kg xylose depending on plant size and number of annual operational hours.

  • 185.
    Magnusson, Björn
    et al.
    Scandinavian Biogas, Stockholm, Sweden.
    Ekstrand, Eva-Maria
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten.
    Karlsson, Anna
    Scandinavian Biogas, Stockholm, Sweden.
    Ejlertsson, Jörgen
    Linköpings universitet, Institutionen för tema, Tema Miljöförändring. Linköpings universitet, Filosofiska fakulteten. Scandinavian Biogas, Stockholm, Sweden.
    Combining high-rate aerobic wastewater treatment with anaerobic digestion of waste activated sludge at a pulp and paper mill2018Inngår i: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 77, nr 8, s. 2068-2076Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The activated sludge process within the pulp and paper industry is generally run to minimize the production of waste activated sludge (WAS), leading to high electricity costs from aeration and relatively large basin volumes. In this study, a pilot-scale activated sludge process was run to evaluate the concept of treating the wastewater at high rate with a low sludge age. Two 150 L containers were used, one for aeration and one for sedimentation and sludge return. The hydraulic retention time was decreased from 24 hours to 7 hours, and the sludge age was lowered from 12 days to 2–4 days. The methane potential of the WAS was evaluated using batch tests, as well as continuous anaerobic digestion (AD) in 4 L reactors in mesophilic and thermophilic conditions. Wastewater treatment capacity was increased almost four-fold at maintained degradation efficiency. The lower sludge age greatly improved the methane potential of the WAS in batch tests, reaching 170 NmL CH4/g VS at a sludge age of 2 days. In addition, the continuous AD showed a higher methane production at thermophilic conditions. Thus, the combination of high-rate wastewater treatment and AD of WAS is a promising option for the pulp and paper industry.

    Fulltekst tilgjengelig fra 2019-04-30 12:23
  • 186. Malinovskiy, Dmitry
    et al.
    Rodushkin, Ilya
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Öhlander, Björn
    Determination of the isotopic composition of molybdenum in the bottom sediments of freshwater basins2007Inngår i: Geochemistry International, ISSN 0016-7029, E-ISSN 1556-1968, Vol. 45, nr 4, s. 381-389Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents the results of measurements of the Mo isotopic composition in the bottom sediments (BS) of freshwater basins. Mo isotopic ratios were measured using a multicollector inductively coupled plasma mass spectrometer (MC ICP MS). Efficient methods were used in this study for Mo separation from the elements of the sample matrix and correction for instrumental mass discrimination. This allowed us to achieve a high accuracy of 0.06, 0.08, and 0.14‰ (2 σ) for the measurement of 97Mo/95Mo, 98Mo/95Mo, and 100Mo/95Mo, respectively. The range of variations in Mo isotope ratios observed in the collected BS columns was ∼2.2‰ in terms of δ97Mo/95Mo. The results obtained here suggest that geochemical processes occurring during Mo migration with land water can change the isotopic composition of Mo. It is pointed out that the potential use of Mo isotopic systematics for reconstructions of redox conditions in seawater over the geologic past requires the quantification of isotopic effects of Mo accompanying its migration on land and the extent of possible variations in the isotopic composition of Mo entering the ocean.

  • 187.
    Mamma, Diommi
    et al.
    NTUA.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Biotechnological Potential of Citrus Peels2014Inngår i: Industrial Microbiology: Microbes in Process, Nova Science Publishers, Incorporated , 2014, s. 59-92Kapittel i bok, del av antologi (Fagfellevurdert)
  • 188.
    Mamma, Diommi
    et al.
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Biotransformation of citrus by-products into value added products2014Inngår i: Waste and Biomass Valorization, ISSN 1877-2641, E-ISSN 1877-265X, Vol. 5, nr 4, s. 529-549Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Citrus by-products are the processing wastes generated after citrus juice extraction and constitute about 50 % of fresh fruit weight. This solid residue comprised of peel (flavedo and albedo), pulp (juice sac residue), rag (membranes and cores) and seeds. The disposal of the fresh peels is becoming a major problem to many factories. Usually, citrus juice industries dry the residue and it is either sold as raw material for pectin extraction or pelletized for animal feeding, though none of these processes is very profitable. This residual material is a poor animal feed supplement because of its extremely low protein content and high amount of sugar. The application of agroindustrial by-products in bioprocesses offers a wide range of alternative substrates, thus helping solve pollution problems related to their disposal. This article reviews attempts that have been made to use citrus by-products to generate several value-added products, such as essential oils, pectin, enzymes, single cell protein, natural antioxidants, ethanol, organic acids, and prebiotics.

  • 189.
    Mandenius, Carl-Fredrik
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teknisk biologi. Linköpings universitet, Tekniska högskolan.
    Titchener-Hooker, Nigel J.University College London, UK.
    Measurement, Monitoring, Modelling and Control of Bioprocesses2013Collection/Antologi (Fagfellevurdert)
    Abstract [en]

    Automated Measurement and Monitoring of Bioprocesses: Key Elements of the M3C Strategy, by Bernhard Sonnleitner Automatic Control of Bioprocesses, by Marc Stanke, Bernd Hitzmann An Advanced Monitoring Platform for Rational Design of Recombinant Processes, by G. Striedner, K. Bayer Modelling Approaches for Bio-Manufacturing Operations, by Sunil Chhatre Extreme Scale-Down Approaches for Rapid Chromatography Column Design and Scale-Up During Bioprocess Development, by Sunil Chhatre Applying Mechanistic Models in Bioprocess Development, by Rita Lencastre Fernandes, Vijaya Krishna Bodla, Magnus Carlquist, Anna-Lena Heins, Anna Eliasson Lantz, Gürkan Sin and Krist V. Gernaey Multivariate Data Analysis for Advancing the Interpretation of Bioprocess Measurement and Monitoring Data, by Jarka Glassey Design of Pathway-Level Bioprocess Monitoring and Control Strategies Supported by Metabolic Networks, by Inês A. Isidro, Ana R. Ferreira, João J. Clemente, António E. Cunha, João M. L. Dias, Rui Oliveira Knowledge Management and Process Monitoring of Pharmaceutical Processes in the Quality by Design Paradigm, by Anurag S Rathore, Anshuman Bansal, Jaspinder Hans The Choice of Suitable Online Analytical Techniques and Data Processing for Monitoring of Bioprocesses, by Ian Marison, Siobhán Hennessy, Róisín Foley, Moira Schuler, Senthilkumar Sivaprakasam, Brian Freeland

  • 190.
    Mathis-Lilley, J. J.
    et al.
    Iowa State University.
    Berglund, Kris
    Contact nucleation from aqueous potash alum solutions1985Inngår i: AIChE Journal, ISSN 0001-1541, E-ISSN 1547-5905, Vol. 31, nr 5, s. 865-867Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Based on experimental results, it is concluded that potash alum contact nuclei grow at a size-independent rate in a system where flow does not result in crystal collisions. Both initial size and growth rate distributions are present for contact nuclei of potash alum. Curvature in semilogarithmic population density-size plots from continuous potash alum crystallization studies may be due to growth rate dispersion and not size-dependent growth.

  • 191.
    Matsakas, Leonidas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Antonopoulou, Io
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Evaluation of Myceliopthora thermophila as an enzyme factory for the production of thermophilic cellulolytic enzymes2015Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 10, nr 3, s. 5140-5158Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Enzymatic hydrolysis is a key step in bioethanol production. Efficient hydrolysis requires a consortium of different enzymes that are able to hydrolyze cellulose and hemicellulose into fermentable sugars. Myceliopthora thermophila is a promising candidate for the production of thermophilic cellulolytic enzymes, the use of which could reduce the cost of ethanol production. The growth conditions of the fungus were optimized in order to achieve increased secretion of extracellular cellulases. Optimal conditions were found to be 7.0% w/v brewer’s spent grain as the carbon source and 0.4% w/v ammonium sulfate as the nitrogen source. The cellulases obtained were characterized for their optimum activity. The optimum temperature and pH for cellulase activity are 65 °C and pH 5.5, respectively. Studies on thermal inactivation of the crude extract showed that the cellulases of M. thermophila are stable for temperatures up to 60 °C. At this temperature the half-life was found to be as high as 27 h. Enzymatic hydrolysis of cellulose resulted in 31.4% hydrolysis yield at 60 °C after 24 h of incubation. Finally, the recalcitrance constant for cellulose and cellulose pretreated with ionic liquids was calculated to be 5.46 and 2.69, respectively.

  • 192.
    Matsakas, Leonidas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Bonturi, Nemailla
    Department of Materials and Bioprocess Engineering, School of Chemical Engineering, State University of Campinas.
    Miranda, Everson Alves
    Department of Materials and Bioprocess Engineering, School of Chemical Engineering, State University of Campinas.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    High concentrations of dried sorghum stalks as a biomass feedstock for single cell oil production by Rhodosporidium toruloides2015Inngår i: Biotechnology for Biofuels, ISSN 1754-6834, E-ISSN 1754-6834, Vol. 8, artikkel-id 8:6Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background:Environmental crisis and concerns for energy security have made the research for renewable fuels that will substitute the usage of fossil fuels an important priority. Biodiesel is a potential substitute for petroleum, but its feasibility is hindered by the utilization of edible vegetable oil as raw material, which is responsible for alarge fraction of the production cost and fosters the food versus fuel competition. Microbial oils are an interesting alternative as they do not compete with food production, and low cost renewable materials could serve as raw materials during cultivation of microorganisms. Sweet sorghum is an excellent candidate as substrate for microbial oil production, as it possesses high photosynthetic activity yielding high amounts of soluble and insoluble carbohydrates, and does not require high fertilization and irrigation rates.Results: Initially the ability of sweet sorghum to fully support yeast growth, both as a carbon and nitrogen source was evaluated. It was found that addition of an external nitrogen source had a negative impact on single cell oil (SCO) production yields, which has a positive effect on the process economics. Subsequently the effect of thepresence of a distinct saccharification step on SCO was examined. The presence of an enzymatic saccharification step prior to SCO production improved the production of SCO, especially in high solid concentrations. Removal of solids was also investigated and its positive effect on SCO production was also demonstrated. When juice from 20%w/w enzymatically liquefied sweet sorghum was used as the raw material, SCO production was 13.77 g/L. To the best of our knowledge this is one of the highest SCO titers reported in the literature when renewable raw materials were utilized.Conclusions: The use of sweet sorghum at high solid concentrations as a feedstock for the efficient production of SCO by Rhodosporidium toruloides was demonstrated. Moreover, addition of enzymes not only led to liquefaction of sweet sorghum and permitted liquid fermentation, but also enhanced lipid production by 85.1% and 15.9%when dried stalks or stalk juice was used, respectively.

  • 193.
    Matsakas, Leonidas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Ethanol Production from Enzymatically Treated Dried Food Waste Using Enzymes Produced On-Site2015Inngår i: Sustainability, ISSN 2071-1050, E-ISSN 2071-1050, Vol. 7, nr 2, s. 1446-1458Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The environmental crisis and the need to find renewable fuel alternatives have made production of biofuels an important priority. At the same time, the increasing production of food waste is an important environmental issue. For this reason, production of ethanol from food waste is an interesting approach. Volumes of food waste are reduced and ethanol production does not compete with food production. In this work, we evaluated the possibility of using source-separated household food waste for the production of ethanol. To minimize the cost of ethanol production, the hydrolytic enzymes that are necessary for cellulose hydrolysis were produced in-house using the thermophillic fungus Myceliophthora thermophila. At the initial stage of the study, production of these thermophilic enzymes was studied and optimized, resulting in an activity of 0.28 FPU/mL in the extracellular broth. These enzymes were used to saccharify household food waste at a high dry material consistency of 30% w/w, followed by fermentation. Ethanol production reached 19.27 g/L with a volumetric productivity of 0.92 g/L·h, whereas only 5.98 g/L of ethanol was produced with a volumetric productivity of 0.28 g/L·h when no enzymatic saccharification was used.

  • 194.
    Matsakas, Leonidas
    et al.
    National Technical University of Athens.
    Christakopoulos, Paul
    National Technical University of Athens.
    Fermentation of liquefacted hydrothermally pretreated sweet sorghum bagasse to ethanol at high-solids content2013Inngår i: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 127, s. 202-208Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The ability of sweet sorghum bagasse to be utilized as feedstock for ethanol production at high initial dry matter concentration was investigated. In order to achieve high enzymatic hydrolysis yield, a hydrothermal pretreatment prior to liquefaction and saccharification was applied. Response surface methodology had been employed in order to optimize the pretreatment step, taking into account the yield of cellulose hydrolysis. Liquefaction of the pretreated bagasse was performed at a specially designed liquefaction chamber at 50 °C for either 12 or 24 h using an enzyme loading of 10 FPU/g·DM and 18% DM. Fermentation of liquefacted bagasse was not affected by liquefaction duration and leaded to an ethanol production of 41.43 g/L and a volumetric productivity of 1.88 g/L h. The addition of extra enzymes at the start up of SSF enhanced both ethanol concentration and volumetric productivity by 16% and 17% after 12 and 24 h saccharification, respectively.

  • 195.
    Matsakas, Leonidas
    et al.
    BIOtechMASS Unit, 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.
    Optimization of ethanol production from high dry matter liquefied dry sweet sorghum stalks2013Inngår i: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 51, s. 91-98Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The ability of sweet sorghum to be utilized as feedstock for ethanol production at high initial dry material concentration was investigated. Sweet sorghum, after being dried, was liquefacted employing commercial cellulase solution Celluclast® 1.5L, in order submerged fermentation to be permitted under high-solids concentrations. The presence of a separate enzymatic liquefaction step at 350 kg m−3 initial DM enhanced both ethanol production and productivity by 29.76% and 250%, respectively. Response surface methodology, based on the central composite design was applied to explore the combined effect of liquefaction duration and enzyme loading in order liquefaction conditions to be optimized. When the optimum conditions were tested using an enzyme load of 8.32 FPU g−1 of dry material for 8.6 h at 50 °C, high productivity (3.0 kg m−3 h−1) and final ethanol production (62.5 kg m−3) were achieved.

  • 196.
    Matsakas, Leonidas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Gao, Qiuju
    Department of Chemistry, Umeå University.
    Jansson, Stina
    Department of Chemistry, Umeå University.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Green conversion of municipal solid wastes into fuels and chemicals2017Inngår i: Electronic Journal of Biotechnology, ISSN 0717-3458, E-ISSN 0717-3458, Vol. 26, s. 69-83Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Presently, the society is facing a serious challenge for the effective management of the increasing amount of produced municipal solid wastes. The accumulated waste has caused a series of environmental problems such as uncontrolled release of greenhouse gases. Moreover, the increasing amount has resulted in a shortage of areas available for waste disposal, resulting in a non-sustainable waste management. These problems led to serious public concerns which in turn resulted in political actions aiming to reduce the amount of the waste ending in the environment. These actions aim to promote sustainable waste management solutions. The main objective of these policies is to promote recycling of municipal solid waste and also the conversion of waste to energy and valuable chemicals. These conversions can be performed by using either biological (e.g. anaerobic digestion) or thermochemical processes (e.g. pyrolysis). The research efforts during the last years have been fruitful and many publications demonstrate the effective conversation of municipal solid waste to energy and chemicals. These processes are discussed in the current review article together with the change of waste policy that was implemented in EU during the last years.

  • 197.
    Matsakas, Leonidas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Giannakou, Maria
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Vörös, Dimitrij
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Effect of synthetic and natural media on lipid production from Fusarium oxysporum2017Inngår i: Electronic Journal of Biotechnology, ISSN 0717-3458, E-ISSN 0717-3458, Vol. 30, s. 95-102Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background

    Dependence on fossil resources, for the production of fuels and energy, has resulted in environmental and financial problems, which require our immediate action in order to reverse the situation. Use of renewable sources for the production of fuels and energy is an important alternative with biodiesel remains as one of the promising options. Aim of this work is to evaluate the fungus Fusarium oxysporum for its potentials to accumulate microbial lipids when grown on synthetic media and saccharified sweet sorghum stalks.

    Results

    The effect of different carbon sources, nitrogen sources and C/N ratio on the lipid production was initially examined, which resulted in a lipid concentration of 4.4 g/L, with lipid content of 42.6% w/w. Sweet sorghum stalks were able to support growth and lipid production of the fungus, both as carbon source and as nitrogen source. It was also shown that saccharification of the dried stalks is an important step to increase lipid production. Removal of the remaining stalk solids enabled the lipid production during cultivation in increased initial solids of up to 16 w/w. This resulted in a lipid production of 3.81 g/L.

    Conclusions

    It was demonstrated that F. oxysporum can be used as an efficient oleaginous microorganism, with sweet sorghum serving as an excellent raw material for the cultivation of the fungus. The lipids obtained during this work were also found to have a fatty acid profile with good potentials to be used for biodiesel production.

  • 198.
    Matsakas, Leonidas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Hruzova, Katerina
    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.
    Biological Production of 3-Hydroxypropionic Acid: An Update on the Current Status2018Inngår i: Fermentation, ISSN 2311-5637, Vol. 4, nr 1, artikkel-id 13Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The production of high added-value chemicals from renewable resources is a necessity inour attempts to switch to a more sustainable society. 3-Hydroxypropionic acid (3HP) is a promisingmolecule that can be used for the production of an important array of high added-value chemicals,such as 1,3-propanediol, acrylic acid, acrylamide, and bioplastics. Biological production of 3HP hasbeen studied extensively, mainly from glycerol and glucose, which are both renewable resources.To enable conversion of these carbon sources to 3HP, extensive work has been performed to identifyappropriate biochemical pathways and the enzymes that are involved in them. Novel enzymeshave also been identified and expressed in host microorganisms to improve the production yieldsof 3HP. Various process configurations have also been proposed, resulting in improved conversionyields. The intense research efforts have resulted in the production of as much as 83.8 g/L 3HP fromrenewable carbon resources, and a system whereby 3-hydroxypropionitrile was converted to 3HPthrough whole-cell catalysis which resulted in 184.7 g/L 3HP. Although there are still challengesand difficulties that need to be addressed, the research results from the past four years have been animportant step towards biological production of 3HP at the industrial level.

  • 199.
    Matsakas, Leonidas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Karnaouri, Anthi C
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Cwirzen, Andrzej
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Formation of Lignin Nanoparticles by Combining Organosolv Pretreatment of Birch Biomass and Homogenization Processes2018Inngår i: Molecules, ISSN 1420-3049, E-ISSN 1420-3049, Vol. 23, nr 7, artikkel-id 1822Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Valorization of lignocellulosic biomass into a biorefinery scheme requires the use of all biomass components; in this, the lignin fraction is often underutilized. Conversion of lignin to nanoparticles is an attractive solution. Here, we investigated the effect of different lignin isolation processes and a post-treatment homogenization step on particle formation. Lignin was isolated from birch chips by using two organosolv processes, traditional organosolv (OS) and hybrid organosolv-steam explosion (HOS-SE) at various ethanol contents. For post-treatment, lignin was homogenized at 500 bar using different ethanol:water ratios. Isolation of lignin with OS resulted in unshaped lignin particles, whereas after HOS-SE, lignin micro-particles were formed directly. Addition of an acidic catalyst during HOS-SE had a negative impact on the particle formation, and the optimal ethanol content was 50⁻60% v/v. Homogenization had a positive effect as it transformed initially unshaped lignin into spherical nanoparticles and reduced the size of the micro-particles isolated by HOS-SE. Ethanol content during homogenization affected the size of the particles, with the optimal results obtained at 75% v/v. We demonstrate that organosolv lignin can be used as an excellent starting material for nanoparticle preparation, with a simple method without the need for extensive chemical modification. It was also demonstrated that tuning of the operational parameters results in nanoparticles of smaller size and with better size homogeneity.

  • 200.
    Matsakas, Leonidas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Loizidou, Maria
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Kekos, Dimitris
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Utilization of Household Food Waste for the production of ethanol at high dry material content2014Inngår i: Biotechnology for Biofuels, ISSN 1754-6834, E-ISSN 1754-6834, Vol. 7, nr 1, artikkel-id 4Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    BackgroundEnvironmental issues and shortage of fossil fuels have turned the public interest to the utilization of renewable, environmentally friendly fuels, such as ethanol. In order to minimize the competition between fuels and food production, researchers are focusing their efforts to the utilization of wastes and by-products as raw materials for the production of ethanol. household food wastes are being produced in great quantities in European Union and their handling can be a challenge. Moreover, their disposal can cause severe environmental issues (for example emission of greenhouse gasses). On the other hand, they contain significant amounts of sugars (both soluble and insoluble) and they can be used as raw material for the production of ethanol. ResultsHousehold food wastes were utilized as raw material for the production of ethanol at high dry material consistencies. A distinct liquefaction/saccharification step has been included to the process, which rapidly reduced the viscosity of the high solid content substrate, resulting in better mixing of the fermenting microorganism. This step had a positive effect in both ethanol production and productivity, leading to a significant increase in both values, which was up to 40.81% and 4.46 fold, respectively. Remaining solids (residue) after fermentation at 45% w/v dry material (which contained also the unhydrolyzed fraction of cellulose), were subjected to a hydrothermal pretreatment in order to be utilized as raw material for a subsequent ethanol fermentation. This led to an increase of 13.16% in the ethanol production levels achieving a final ethanol yield of 107.58 g/kg dry material. ConclusionsIn conclusion, the ability of utilizing household food waste for the production of ethanol at elevated dry material content has been demonstrated. A separate liquefaction/saccharification process can increase both ethanol production and productivity. Finally, subsequent fermentation of the remaining solids could lead to an increase of the overall ethanol production yield.

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