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  • 201.
    Matsakas, Leonidas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Nitsos, Christos
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Raghavendran, Vijayendran
    Division of Industrial Biotechnology, Department of Biology and Biological Engineering, Chalmers University of Technology, Göteborg.
    Yakimenko, Olga
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Persson, Gustav
    Department of Physics, Chalmers University of Technology, Göteborg.
    Olsson, Eva
    Department of Physics, Chalmers University of Technology, Göteborg.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Olsson, Lisbeth
    Division of Industrial Biotechnology, Department of Biology and Biological Engineering, Chalmers University of Technology, Göteborg.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    A novel hybrid organosolv: steam explosion method for the efficient fractionation and pretreatment of birch biomass2018Inngår i: Biotechnology for Biofuels, ISSN 1754-6834, E-ISSN 1754-6834, Vol. 11, nr 1, artikkel-id 160Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The main role of pretreatment is to reduce the natural biomass recalcitrance and thus enhance saccharification yield. A further prerequisite for efficient utilization of all biomass components is their efficient fractionation into well-defined process streams. Currently available pretreatment methods only partially fulfill these criteria. Steam explosion, for example, excels as a pretreatment method but has limited potential for fractionation, whereas organosolv is excellent for delignification but offers poor biomass deconstruction.

    Results

    In this article, a hybrid method combining the cooking and fractionation of conventional organosolv pretreatment with the implementation of an explosive discharge of the cooking mixture at the end of pretreatment was developed. The effects of various pretreatment parameters (ethanol content, duration, and addition of sulfuric acid) were evaluated. Pretreatment of birch at 200 °C with 60% v/v ethanol and 1% w/wbiomass H2SO4 was proven to be the most efficient pretreatment condition yielding pretreated solids with 77.9% w/w cellulose, 8.9% w/w hemicellulose, and 7.0 w/w lignin content. Under these conditions, high delignification of 86.2% was demonstrated. The recovered lignin was of high purity, with cellulose and hemicellulose contents not exceeding 0.31 and 3.25% w/w, respectively, and ash to be < 0.17% w/w in all cases, making it suitable for various applications. The pretreated solids presented high saccharification yields, reaching 68% at low enzyme load (6 FPU/g) and complete saccharification at high enzyme load (22.5 FPU/g). Finally, simultaneous saccharification and fermentation (SSF) at 20% w/w solids yielded an ethanol titer of 80 g/L after 192 h, corresponding to 90% of the theoretical maximum.

    Conclusions

    The novel hybrid method developed in this study allowed for the efficient fractionation of birch biomass and production of pretreated solids with high cellulose and low lignin contents. Moreover, the explosive discharge at the end of pretreatment had a positive effect on enzymatic saccharification, resulting in high hydrolyzability of the pretreated solids and elevated ethanol titers in the following high-gravity SSF. To the best of our knowledge, the ethanol concentration obtained with this method is the highest so far for birch biomass.

  • 202.
    Matsakas, Leonidas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Nitsos, Christos
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Vörös, Dimitrij
    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.
    High-Titer Methane from Organosolv-Pretreated Spruce and Birch2017Inngår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 10, nr 3, artikkel-id 263Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The negative impact of fossil fuels and the increased demand for renewable energy sources has led to the use of novel raw material sources. Lignocellulosic biomass could serve as a possible raw material for anaerobic digestion and production of biogas. This work is aimed at using forest biomass, both softwood (spruce) and hardwood (birch), as a raw material for anaerobic digestion. We examined the effect of different operational conditions for the organosolv pretreatment (ethanol content, duration of treatment, and addition of acid catalyst) on the methane yield. In addition, we investigated the effect of addition of cellulolytic enzymes during the digestion. We found that inclusion of an acid catalyst during organosolv pretreatment improved the yields from spruce, but it did not affect the yields from birch. Shorter duration of treatment was advantageous with both materials. Methane yields from spruce were higher with lower ethanol content whereas higher ethanol content was more beneficial for birch. The highest yields obtained were 185 mL CH4/g VS from spruce and 259.9 mL CH4/g VS from birch. Addition of cellulolytic enzymes improved these yields to 266.6 mL CH4/g VS and 284.2 mL CH4/g VS, respectively.

  • 203.
    Matsakas, Leonidas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Novak, Katharina
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Enman, Josefine
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Acetate-detoxification of wood hydrolysates with alkali tolerant Bacillus sp. as a strategy to enhance the lipid production from Rhodosporidium toruloides2017Inngår i: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 242, s. 287-294Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of the current work was to convert an acetate-rich hemicellulose liquid fraction (LF) from hot-water extraction of Betula pendula to oils for biodiesel, with Rhodosporidium toruloides. The toxicity of acetate was circumvented by biological detoxification with an isolated alkali-tolerant and acetate-resistant Bacillus sp. strain. Removal of other lignocellulose-derived inhibitors, such as furfural and phenols, was evaluated by two strategies; an activated carbon (AC) treatment of the undiluted LF, and dilution of the LF by 25% (0.75LF) and 50%. (0.50LF). The bacterium consumed most of the acetic acid in 6-8 days in the treated or diluted media, which were subsequently used for cultivation of the yeast, for conversion of sugars to oils. The oil concentration reached 2.8 and 1.8 g/L, in the AC LF and 0.75LF medium, respectively. In comparison, the oil accumulation in the same media without prior cultivation of Bacillus sp. was 0.86 and 0.03 g/L, respectively.

  • 204.
    Matsakas, Leonidas
    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.
    Evaluation of dried sweet sorghum stalks as raw material for methane production2014Inngår i: BioMed Research International, ISSN 2314-6133, E-ISSN 2314-6141, Vol. 2014, artikkel-id 731731Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The potential of utilizing dried sweet sorghum stalks as raw material for anaerobic digestion has been evaluated. Two different treatments were tested, a mild thermal and an enzymatic, alone or in combination. Thermal pretreatment was found to decrease the methane yields, whereas one-step enzymatic treatment resulted in a significant increase of 15.1% comparing to the untreated sweet sorghum. Subsequently, in order to increase the total methane production, the combined effect of enzyme load and I/S on methane yields from sweet sorghum was evaluated by employing response surface methodology. The obtained model showed that the maximum methane yield that could be achieved is 296 mL CH4/g VS at I/S ratio of 0.35 with the addition of 11.12 FPU/g sweet sorghum.

  • 205.
    Matsakas, Leonidas
    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.
    Sequential parametric optimization of methane production from different sources of forest raw material2015Inngår i: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 6, artikkel-id 1163Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The increase in environmental problems and the shortage of fossil fuels have led to the need for action in the development of sustainable and renewable fuels. Methane is produced through anaerobic digestion of organic materials and is a biofuel with very promising characteristics. The success in using methane as a biofuel has resulted in the operation of several commercial-scale plants and the need to exploit novel materials to be used. Forest biomass can serve as an excellent candidate for use as raw material for anaerobic digestion. During this work, both hardwood and softwood species—which are representative of the forests of Sweden—were used for the production of methane. Initially, when untreated forest materials were used for the anaerobic digestion, the yields obtained were very low, even with the addition of enzymes, reaching a maximum of only 40 mL CH4/g VS when birch was used. When hydrothermal pretreatment was applied, the enzymatic digestibility improved up to 6.7 times relative to that without pretreatment, and the yield of methane reached up to 254 mL CH4/g VS. Then the effect of chemical/enzymatic detoxification was examined, where laccase treatment improved the methane yield from the more harshly pretreated materials while it had no effect on the more mildly pretreated material. Finally, addition of cellulolytic enzymes during the digestion improved the methane yields from spruce and pine, whereas for birch separate saccharification was more beneficial. To achieve high yields in spruce 30 filter paper units (FPU)/g was necessary, whereas 15 FPU/g was enough when pine and birch were used. During this work, the highest methane yields obtained from pine and birch were 179.9 mL CH4/g VS and 304.8 mL CH4/g VS, respectively. For mildly and severely pretreated spruce, the methane yields reached 259.4 mL CH4/g VS and 276.3 mL CH4/g VS, respectively. We have shown that forest material can serve as raw material for efficient production of methane. The initially low yields from the untreated materials were significantly improved by the introduction of a hydrothermal pretreatment. Moreover, enzymatic detoxification was beneficial, but mainly for severely pretreated materials. Finally, enzymatic saccharification increased the methane yields even further.

  • 206.
    Matsakas, Leonidas
    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.
    Strategies for Enhanced Biogas Generation through Anaerobic Digestion of Forest Material: An Overview2016Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, nr 2, s. 5482-5499Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Incorporation of biofuels into the existing selection of fuels is a very important measure to slow down environmental destruction and to counter the imminent fossil fuel shortage. Biogas is a very interesting option for use in both electricity and heat production, and also as a fuel for vehicles. The positive fuel characteristics of biogas and the high yields of biogas obtained from traditional raw materials (e.g., animal manure) have resulted in operation of several commercial units around the globe. On the other hand, there is an increased demand for biogas production which, for the need to be met, should have renewable resources incorporated into it. Forest materials are an interesting candidate, and there is a rising interest in the research and industrial communities to exploit them as raw materials for anaerobic digestion in biogas production. In this review article, we aim to give the reader an insight into the most recent processes for conversion of various sources of forest materials into biogas.

  • 207.
    Matsakas, Leonidas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Sterioti, Aikaterini-Aithra
    Biotechnology Laboratory, School of Chemical Engineering, 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.
    Use of dried sweet sorghum for the efficient production of lipids by the yeast Lipomyces starkeyi CBS 18072014Inngår i: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 62, s. 367-372Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The ability of the oleaginous yeast Lipomyces starkeyi to efficiently produce lipids when cultivated on saccharified sweet sorghum stalks juice was evaluated. Initially the production of lipids using synthetic media mimicking sweet sorghum stalks has been studied and optimized concerning the nitrogen source and the C:N ratio. Under optimum conditions (yeast extract as nitrogen source and C:N ratio of 190) the lipid production reached 5.81 g/L with a lipid content of 47.3% (w/w) from a mixture of sucrose, glucose and fructose, mimicking the sugar composition of sorghum. When cultivated on sweet sorghum stalks juice, it was observed that no external nitrogen addition was necessary which could result in substantial decrease of the initial C:N ratio. Moreover a distinct saccharification process prior to yeast cultivation improved the lipid production yield as it resulted in an increase of the C:N ratio. The highest lipid production, which was 6.40 g/L with a lipid content of 29.5% (w/w), was obtained when juice from saccharified sweet sorghum stalks at an initial sorghum content of 12% (w/w) was used as feedstock.

  • 208.
    Matsakas, Leonidas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Topakas, Evangelos
    National Technical University of Athens.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    New trends in microbial production of 3-hydroxypropionic acid2014Inngår i: Current Biochemical Engineering, ISSN 2212-7119, Vol. 1, nr 2, s. 141-154Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Production of bio-based chemicals nowadays is more crucial than ever. 3-Hydroxypropionic acid can serve as a building block chemical for the production of other high added value chemicals, fact that have made it as one of the most valuable chemicals according to US DOE. Recently, researchers have turned their interest in the construction of a microbial cell factory that will be capable of producing 3-hydroxypropionic acid from renewable raw materials. Most of the work is dedicated in the utilization of glycerol as raw material by employing either Escherichia coli or Klebsiella pneumoniae strains. Several genes were tested and evaluated and different cultivation techniques were applied. During the last few years, promising levels of 3- hydroxypropionic acid were obtained, however more effort has to be dedicated on this direction of the commercialization of the process that seems to be closer than even before.

  • 209.
    McMahon, Paula M.
    et al.
    Iowa State University.
    Cerreta, Michael K.
    Iowa State University.
    Berglund, Kris
    Larson, Maurice A.
    Iowa State University.
    A constant-temperature Raman cell for the study of supersaturated aqueous solutions1986Inngår i: Applied Spectroscopy, ISSN 0003-7028, E-ISSN 1943-3530, Vol. 40, nr 2, s. 282-283Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In order that the phenomena of crystal nucleation and growth from solution can be fully understood, the current knowledge of supersaturated solution structure must be extended. Previous studies on Raman spectroscopy of aqueous metal nitrate solutions indicated the presence of solvated ions, solvent separated ion pairs, contact ion pairs, and ion agglomerates as a function of concentration. Unfortunately, the concentration range of these studies did not include supersaturated solutions. It is the purpose of this work to describe an experimental technique which allows the study of supersaturated solutions.

  • 210.
    McMahon, Paula M.
    et al.
    Iowa State University.
    Larson, Maurice A.
    Iowa State University.
    Hussmann, Glenn A.
    Iowa State University.
    Berglund, Kris
    Cerreta, Michael K.
    Iowa State University.
    Raman spectroscopic studies of the structure of supersaturated nitrate and phosphate solutions1984Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Laser Raman spectroscopy was used to study aqueous solutions of potassium nitrate, sodium nitrate, and ammonium dihydrogen phosphate. Concentrations were varied from dilute to supersaturated. In all cases additional order was found as the concentration was increased. The implications for the relationship between solution structure and crystallization phenomena (nucleation and growth) are discussed.

  • 211.
    McMahon, P.M.
    et al.
    Iowa State University.
    Berglund, Kris
    Larson, M.A.
    Iowa State University.
    Raman spectroscopic studies of the structure of supersaturated KNO//3 solutions1984Inngår i: Industrial Crystallization 84: proceedings of the 9th Symposium on industrial crystallization, the Hague, the Netherlands, September 25-28, 1984 / [ed] S.J. Jančić; E.J. de Jong, Amsterdam: Elsevier, 1984, s. 229-232Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Laser Raman spectroscopy was used to study the nu //1 (A//1) band of aqueous potassium nitrate solution. The purpose was to establish the relationship between solution structure, nucleation and growth. Two bands were determined that exist at 1049 cm** minus **1 (the free nitrate ion) and 1050. 5 cm** minus **1 (a more ordered species). The band at 1050. 5 cm** minus **1 increased in magnitude as concentration was increased into the supersaturation region. Solutions containing 200 ppm Cr**3** plus were also studied and this impurity was found to suppress the formation of the species at 1050. 5 cm** minus **1.

  • 212.
    Mesfun, Sennai
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Lundgren, Joakim
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Grip, Carl-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Toffolo, Andrea
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Kudahettige-Nilsson, Rasika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Black liquor fractionation for biofuels production: A techno-economic assessment2014Inngår i: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 166, s. 508-517Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The hemicelluloses fraction of black liquor is an underutilized resource in many chemical pulp mills. It is possible to extract and separate the lignin and hemicelluloses from the black liquor and use the hemicelluloses for biochemical conversion into biofuels and chemicals. Precipitation of the lignin from the black liquor would consequently decrease the thermal load on the recovery boiler, which is often referred to as a bottleneck for increased pulp production. The objective of this work is to techno-economically evaluate the production of sodium-free lignin as a solid fuel and butanol to be used as fossil gasoline replacement by fractionating black liquor. The hydrolysis and fermentation processes are modeled in Aspen Plus to analyze energy and material balances as well as to evaluate the plant economics. A mathematical model of an existing pulp and paper mill is used to analyze the effects on the energy performance of the mill subprocesses.

  • 213.
    Mesfun, Sennai
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Lundgren, Joakim
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Grip, Carl-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Toffolo, Andrea
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Techno-economic evaluation of butanol production via black liquor fractionation2013Konferansepaper (Fagfellevurdert)
  • 214.
    Micael, Karlberg
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teknisk biologi. Linköpings universitet, Tekniska högskolan.
    Soft sensor application on lactate controlled fed-batch cultivation for monoclonal antibody production2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Monoclonal antibody producing cells are of great interest and used frequently in the field of biomedical research, diagnostics and therapy with increasing need for better systems to more efficiently produce antibodies at a lower costs. In this project three fed-batch cultivations of hybridoma cells (HB-8696) were cultured in a stirred tank reactor with the use of a soft sensor to monitor the lactate concentration and as well as a dielectric probe for biomass measurements. In addition, a protocol for growing the inoculum was also successfully produced and a previous batch cultivation was also analyzed which gave crucial information about stoichiometrically relation in the feed medium which was used in the fed-batch cultivations. The BioSenz Analyzer was used for on-line lactate concentration monitoring and was later used to control the feed profile to avoid overflow metabolism in two of the three fed-batch cultivations. However, nothing conclusive could be said about the lactate controller as of yet which needs further research.

  • 215. Miranda, A.
    et al.
    Berglund, Kris
    Recovery of Clostridium thermosulfurogenes produced β-amylase by (hydroxypropyl)methylcellulose partition1990Inngår i: Biotechnology progress (Print), ISSN 8756-7938, E-ISSN 1520-6033, Vol. 6, nr 3, s. 214-219Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A procedure for recovering Clostridium thermosulfurogenes produced β-amylase from fermentation broth by partition was developed. The partition was achieved by addition of ammonium sulfate to an aqueous solution of the enzyme with (hydroxypropyl)methylcellulose. The β-amylase-containing pellet formed upon centrifugation could be redissolved and the polymer recovered by a second salt addition. The process was not dependent on polymer/enzyme solution pH, but it was affected by temperature, polymer nominal molecular weight and loading, and fermentation carbon source. Unlike more traditional aqueous-phase partitions, such as poly(ethylene glycol)/dextran, the current approach appeared to be biospecific.

  • 216.
    Miranda, E.A.
    et al.
    Michigan State University.
    Berglund, Kris
    Development of precipitant agents for precipitation of proteins based on hydrophobic interaction1995Inngår i: Brazilian journal of chemical engineering, ISSN 0104-6632, E-ISSN 1678-4383, Vol. 12, nr 1, s. 1-12Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Precipitation agents were developed to perform protein separation by precipitation based on hydrophobic interaction. They consisted of ligands, saturated linear chains of fatty acids, attached by esterification to a carrier molecule, methylcellulose. Precipitation of bovine serum albumin was achieved at 50 percent saturation of ammonium sulfate. The butyric acid derivative showed a higher efficiency in precipitating this protein than other derivatives tested. There is evidence that the interaction between the protein and the derivatives is hydrophobic.

  • 217.
    Miranda, Everson A.
    et al.
    Michigan State University.
    Berglund, Kris
    Evaluation of column flotation in the downstream processing of fermentation products: recovery of a genetically engineered α-amylase1993Inngår i: Biotechnology progress (Print), ISSN 8756-7938, E-ISSN 1520-6033, Vol. 9, nr 4, s. 411-420Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Flotation is a simple, inexpensive, and versatile unit operation with a largely unexplored potential in biotechnology. There is a general lack of research concerning biotechnological applications in this area, especially in the recovery of fermentation products. Moreover, the few reports in the literature do not consider the modern concept of column flotation as practiced in the mineral industry. We report herein the application of column flotation for the recovery of a Bacillus stearothermophilus α-amylase expressed in Escherichia coli by the use of a food-grade polymer, (hydroxypropyl)methylcellulose (HPMC), and ammonium sulfate. First, the enzyme was removed from the liquid phase by partition to a salted-out HPMC phase. The enzyme-containing polymer flocs were then floated from the liquid. Recovery of active enzyme was as high as 90%, with throughput as high as 94 m3/(h·m2). The floatability of the enzyme from a periplasmic extract was higher than extracellular enzyme in the broth due to the presence of depressors of molecular weight lower than 10 000 in the broth.

  • 218.
    Mu, Liwen
    et al.
    Intelligent Composites Laboratory, Department of Chemical and Biomolecular Engineering, The University of Akron.
    Wu, Jian
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Matsakas, Leonidas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Chen, Minjiao
    Vahidi, Alireza
    Luleå tekniska universitet.
    Grahn, Mattias
    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.
    Zhu, Jiahua
    Intelligent Composites Laboratory, Department of Chemical and Biomolecular Engineering, The University of Akron.
    Shi, Yijun
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lignin from Hardwood and Softwood Biomass as a Lubricating Additive to Ethylene Glycol2018Inngår i: Molecules, ISSN 1420-3049, E-ISSN 1420-3049, Vol. 23, nr 3, artikkel-id 537Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ethylene glycol (EG)-based lubricant was prepared with dissolved organosolv lignin from birch wood (BL) and softwood (SL) biomass. The effects of different lignin types on the rheological, thermal, and tribological properties of the lignin/EG lubricants were comprehensively investigated by various characterization techniques. Dissolving organosolv lignin in EG results in outstanding lubricating properties. Specifically, the wear volume of the disc by EG-44BL is only 8.9% of that lubricated by pure EG. The enhanced anti-wear property of the EG/lignin system could be attributed to the formation of a robust lubrication film and the strong adhesion of the lubricant on the contacting metal surface due to the presence of a dense hydrogen bonding (H-bonding) network. The lubricating performance of EG-BL outperforms EG-SL, which could be attributed to the denser H-bonding sites in BL and its broader molecular weight distribution. The disc wear loss of EG-44BL is only 45.7% of that lubricated by EG-44SL. Overall, H-bonding is the major contributor to the different tribological properties of BL and SL in EG-based lubricants.

  • 219.
    Muraleedharan, Madhu Nair
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Depolymerization of Lignocellulose by Lytic Polysaccharide MonoOxygenases2018Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Lignocellulose biomass is considered as one of the most potential and sustainable sources for the production of value-added chemicals and fuels while replacing the traditional petroleum resources. In a biorefinery, by employing biochemical conversion processes,cellulose present in the biomass is broken down into monomeric sugars which can belater converted into fuels or chemicals. This process is done with the help of different cellulose digesting enzymes (cellulases), isolated from natural cellulolytic organisms suchas saprophytic fungi.

    Lytic polysaccharide monooxygenases (LPMOs) are considered as one of the vital classesof enzymes in the bio-conversion of lignocellulose. They are copper active enzymes present naturally in cellulose degrading fungi. Unlike the traditional cellulases, they havea unique way of breaking cellulose using molecular oxygen or hydrogen peroxide as cosubstratein the presence of a reducing agent. Their ability to enhance the action of other cellulases in depolymerizing the cellulose, make them an integral part of today’s commercial cellulase cocktails.

    This thesis comprises the study about the action of lytic polysaccharide monooxygenaseson various cellulose substrates, both model and natural. The first part of the thesis focuses on the ability of an LPMO (MtLPMO9) and a traditional cellulase (MtEG5A), to act insynergism. The evaluation was done based on the release of oxidized and non-oxidized sugars and also on the ability to liquefy the substrates. It was observed that together, these two enzymes resulted in enhanced release of oxidized and non-oxidized sugars. Both were able to reduce viscosity of the substrates but no further synergistic effect was observed when added together.

    The second part focuses on the ability of LPMOs to accept electrons from lignins for their action of breaking cellulose chains. Three LPMOs, MtLPMO9, PcLPMO9D and NcLPMO9C, lignins from agricultural and forest biomass pretreated by various pretreatment methods were selected. It was demonstrated that lignins, both in isolatedand substrate bound form were able to act indirectly as reducing agents, by releasingsoluble low-molecular-weight molecules that act as mediators between enzyme and bulklignins. The structural and compositional properties of lignins also affected their ability toact as electron donors. In addition, the effect of biomass pretreatment methods on the lignin properties was also studied. The lignins from acid catalyzed organosolv pretreatment were found as the best candidates in supplying electrons to the enzymes.Interestingly, NcLPMO9C was not able to utilize lignins as electron donors requiring further investigation on their mechanism both in vivo and in vitro.

  • 220.
    Muraleedharan, Madhu Nair
    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.
    Erratum: Lytic Polysaccharide Monooxygensases2017Inngår i: Extremophilic Enzymatic Processing of Lignocellulosic Feedstocks to Bioenergy / [ed] Rajesh K. Sani, R. Navanietha Krishnaraj, Springer International Publishing , 2017, s. E1-Kapittel i bok, del av antologi (Fagfellevurdert)
  • 221.
    Muraleedharan, Madhu Nair
    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.
    Lytic Polysaccharide Monooxygensases2017Inngår i: Extremophilic Enzymatic Processing of Lignocellulosic Feedstocks to Bioenergy / [ed] Rajesh K. Sani, R. Navanietha Krishnaraj, Springer International Publishing , 2017, s. 89-98Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    Lytic Polysaccharide Monooxygensaes have now been evolved as one of the most promising enzymes, attracting huge research attention due to their potential use in saccharification of lignocellulosic biomass for the production of fuels and value added chemicals. In the presence of molecular oxygen, these copper depended enzymes break the recalcitrant cellulose chain by a combined oxidative and hydrolytic action, and increase the substrate accessibility for other cellulases to work. This ‘boosting effect’ and ability to act in synergy makes them important subject to research, towards the future goal of sustainable bioeconomy. Diversity of this enzyme group ranges from early discovered chitin and cellulose active ones, to the recently identified hemicellulose and starch active ones. In this chapter we present a brief summary about LPMOs and the findings related to them from their discovery to the recent developments.

  • 222.
    Muraleedharan, Madhu Nair
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Zouraris, Dimitrios
    Laboratory of Physical Chemistry and Applied Electrochemistry, School of Chemical Engineering, National Technical University of Athens, Athens, Greece.
    Karantonis, Antonis
    Laboratory of Physical Chemistry and Applied Electrochemistry, School of Chemical Engineering, National Technical University of Athens, Athens, Greece.
    Topakas, Evangelos
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Sandgren, Mats
    Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Karnaouri, Anthi C.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Effect of lignin fractions isolated from different biomass sources on cellulose oxidation by fungal lytic polysaccharide monooxygenases2018Inngår i: Biotechnology for Biofuels, ISSN 1754-6834, E-ISSN 1754-6834, Vol. 11, artikkel-id 296Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background

    Lytic polysaccharide monooxygenases (LPMOs) are copper-dependent enzymes that oxidatively cleave recalcitrant lignocellulose in the presence of oxygen or hydrogen peroxide as co-substrate and a reducing agent as electron donor. One of the possible systems that provide electrons to the LPMOs active site and promote the polysaccharide degradation involves the mediation of phenolic agents, such as lignin, low-molecular-weight lignin-derived compounds and other plant phenols. In the present work, the interaction of the bulk insoluble lignin fraction extracted from pretreated biomass with LPMOs and the ability to provide electrons to the active site of the enzymes is studied.

    Results

    The catalytic efficiency of three LPMOs, namely MtLPMO9 with C1/C4 regioselectivity, PcLPMO9D which is a C1 active LPMO and NcLPMO9C which is a C4 LPMO, was evaluated in the presence of different lignins. It was correlated with the physicochemical and structural properties of lignins, such as the molecular weight and the composition of aromatic and aliphatic hydroxyl groups. Moreover, the redox potential of lignins was determined with the use of large amplitude Fourier Transform alternating current cyclic voltammetry method and compared to the formal potential of the Cu (II) center in the active site of the LPMOs, providing more information about the lignin-LPMO interaction. The results demonstrated the existence of low-molecular weight lignin-derived compounds that are diffused in the reaction medium, which are able to reduce the enzyme active site and subsequently utilize additional electrons from the insoluble lignin fraction to promote the LPMO oxidative activity. Regarding the bulk lignin fractions, those isolated from the organosolv pretreated materials served as the best candidates in supplying electrons to the soluble compounds and, finally, to the enzymes. This difference, based on biomass pretreatment, was also demonstrated by the activity of LPMOs on natural substrates in the presence and absence of ascorbic acid as additional reducing agent.

    Conclusions

    Lignins can support the action of LPMOs and serve indirectly as electron donors through low-molecular-weight soluble compounds. This ability depends on their physicochemical and structural properties and is related to the biomass source and pretreatment method.

  • 223.
    Muraleedharan, Madhu Nair
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Zouraris, Dimitrios
    National Technical University of Athens.
    Karantonis, Antonis
    National Technical University of Athens.
    Topakas, Evangelos
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Sandgren, Mats
    Swedish University of Agricultural Sciences.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Karnaouri, Anthi C.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Effect of structural properties of lignin isolated from different sources on its efficiency to serve as electron donor of fungal Lytic Polysaccharide Monooxygenases2018Inngår i: Biotechnology for Biofuels, ISSN 1754-6834, E-ISSN 1754-6834Artikkel i tidsskrift (Fagfellevurdert)
  • 224.
    Murphy, Vincent G.
    et al.
    Colorado State University.
    Berglund, Kris
    Modeling growth rate dispersion in a batch sucrose crystallizer1986Inngår i: Industrial and Engineering Chemistry. Fundamentals, ISSN 0019-7874, Vol. 25, nr 1, s. 174-176Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Growth rate data from experiments on sucrose crystals are analyzed for growth rate dispersion (the variation of crystal growth rates within a population). Two competing models are used in this analysis. Experimental results suggest that carefully designed experiments must be performed to distinguish between the two.

  • 225.
    Nair, Ramkumar B
    et al.
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Eh-Hser Nay, Theimya
    Lennartsson, Patrik R.
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Taherzadeh, Mohammad J
    Högskolan i Borås, Akademin för textil, teknik och ekonomi. Biotechnology.
    Waste Bread Valorization Using Edible Filamentous Fungi2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The present study is the first of its kind to use industrial waste bread for ethanol and food-grade filamentous fungal biomass production, with an ‘integrated-biorefinery’ approach for the existing wheat-based ethanol facilities. Four different food-grade fungi such as Neurospora intermedia, Aspergillus oryzae, belonging to ascomycetes and Mucor indicus, Rhizopus oryzae, belonging to zygomycetes, were screened. Initial screening for fungal cultures (without external enzyme saccharification) showed an ethanol yield maximum of 47.8 ±1.1 to 67.3 ±2.1, and 38.7 ±1.1 to 67.7±1.8 mg per g dry substrate loading from whole-grain bread and white-bread respectively, post the enzymatic liquefaction. Scale-up of the N. intermedia fermentation achieved using bench scale airlift reactor showed an ethanol yield maximum of 91.6 ±2.1 and 87.5 ±1.9 mg per g dry substrate loading for whole-grain bread and white-bread respectively.

  • 226.
    Nair, Ramkumar B
    et al.
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Kalif, Mahdi
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Ferreira, Jorge A.
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Taherzadeh, Mohammad J
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Lennartsson, Patrik R.
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Mild-temperature dilute acid pretreatment for integration of first and second generation ethanol processes2017Inngår i: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 245, s. 145-151Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The use of hot-water (100 °C) from the 1st generation ethanol plants for mild-temperature lignocellulose pretreatment can possibly cut down the operational (energy) cost of 2nd generation ethanol process, in an integrated model. Dilute-sulfuric and -phosphoric acid pretreatment at 100 °C was carried out for wheat bran and whole-stillage fibers. Pretreatment time and acid type influenced the release of sugars from wheat bran, while acid-concentration was found significant for whole-stillage fibers. Pretreatment led up-to 300% improvement in the glucose yield compared to only-enzymatically treated substrates. The pretreated substrates were 191–344% and 115–300% richer in lignin and glucan, respectively. Fermentation using Neurospora intermedia, showed 81% and 91% ethanol yields from wheat bran and stillage-fibers, respectively. Sawdust proved to be a highly recalcitrant substrate for mild-temperature pretreatment with only 22% glucose yield. Both wheat bran and whole-stillage are potential substrates for pretreatment using waste heat from the 1st generation process for 2nd generation ethanol.

  • 227.
    Nair, Ramkumar B
    et al.
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Ravula, Vamsikrishna
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Lennartsson, Patrik R.
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Taherzadeh, Mohammad J
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Neurospora intermedia pellets for enhanced ethanol and fungal biomass production from wheat straw2017Inngår i: Proceedings of 39th Symposium on Biotechnology for Fuels and Chemicals, 2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Recent studies at our research group have described an ‘integrated-biorefinery’ model for the existing 1st generation wheat-based ethanol facilities, by using edible filamentous fungus, Neurospora intermedia. The process focuses on the production of 2nd generation ethanol together with fungal biomass (for animal or aquaculture feed applications) from wheat straw. A final ethanol yield of 94% (theoretical maximum based on substrate glucan content) was obtained with N. intermedia fermentation in dilute phosphoric acid pretreated (0.7%w/v acid, 7min at 201±4°C) and enzymatically hydrolyzed (10FPU cellulase/g substrate) straw. Fungal cultivation in liquid straw hydrolysate resulted in a maximum of 3.71±0.11g/L dry fungal biomass. Considering the industrial significance of the fungal process, attempts were made to manipulate N. intermedia to grow as pellet forms in the straw hydrolysate, for the first time. Of the various culture conditions screened, stable pellet morphology was obtained at pH 3.0 to 5.5, resulting in uniform pellets with size ranging from 2.5 to 4.25mm. Fermentation using N. intermedia pellets in the liquid straw hydrolysate, resulted in about 31% increase in the ethanol yield, with an improved glucose assimilation by the pellets (82% reduction) as opposed to filamentous forms (51% reduction), at similar culture conditions. The growth of fungal pellets in presence of inhibitors (at different concentrations of acetic acid and furfural) resulted in about 11% to 45% increase in ethanol production as compared to filamentous forms, at similar growth conditions in the liquid straw hydrolysate. Detailed results on N. intermedia pelletization in liquid straw hydrolysate will be discussed in this presentation.

  • 228.
    Nair, Ramkumar
    et al.
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Lennartsson, Patrik
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Taherzadeh, Mohammad
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Mycelial pellet formation by edible ascomycete filamentous fungi, Neurospora intermedia2016Inngår i: AMB Express, ISSN 2191-0855, E-ISSN 2191-0855, Vol. 6, nr 31, artikkel-id 10.1186/s13568-016-0203-2Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Pellet formation of filamentous fungi in submerged culture is an imperative topic of fermentation research. In this study, we report for the first time the growth of filamentous ascomycete fungus,Neurospora intermedia in its mycelial pellet form. In submerged culture, the growth morphology of the fungus was successfully manipulated into growing as pellets by modifying various cultivation conditions. Factors such as pH (2.0–10.0), agitation rate (100–150 rpm), carbon source (glucose, arabinose, sucrose, and galactose), the presence of additive agents (glycerol and calcium chloride) and trace metals were investigated for their effect on the pellet formation. Of the various factors screened, uniform pellets were formed only at pH range 3.0–4.0, signifying it as the most influential factor for N. intermedia pellet formation. The average pellet size ranged from 2.38 ± 0.12 to 2.86 ± 0.38 mm. The pellet formation remained unaffected by the inoculum type used and its size showed an inverse correlation with the agitation rate of the culture. Efficient glucose utilization was observed with fungal pellets, as opposed to the freely suspended mycelium, proving its viability for fast- fermentation processes. Scale up of the pelletization process was also carried out in bench-scale airlift and bubble column reactors (4.5 L).

  • 229.
    Navrátil, Marián
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teknisk biologi. Linköpings universitet, Tekniska högskolan.
    Cimander, Christian
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teknisk biologi. Linköpings universitet, Tekniska högskolan.
    Mandenius, Carl-Fredrik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teknisk biologi. Linköpings universitet, Tekniska högskolan.
    On-line multisensor monitoring of yogurt and Filmjolk fermentations on production scale2004Inngår i: Journal of Agricultural and Food Chemistry, ISSN 0021-8561, E-ISSN 1520-5118, Vol. 52, nr 3, s. 415-420Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Near-infrared (NIR) spectrometry and electronic nose (EN) data were used for on-line monitoring of yogurt and filmjölk (a Swedish yogurt-like sour milk) fermentations under industrial conditions. The NIR and EN signals were selected by evaluation of principal component analysis loading vectors and further analyzed by studying the variability of the selected principal components. First principal components for the NIR and the EN signals were used for on-line generation of a process trajectory plot visualizing the actual state of fermentation. The NIR signals were also used to set up empirical partial least-squares (PLS) models for prediction of the cultures' pH and titratable acidity (expressed as Thorner degrees, °T). By using five or six PLS factors the models yielded acceptable predictions that could be further improved by increasing the number of reliable and precise calibration data. The presented results demonstrate that the fusion of the NIR and EN signals has a potential for rapid on-line monitoring and assessment of process quality of yogurt fermentation.

  • 230.
    Nikolaivits, Efstratios
    et al.
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, Athens, Greece.
    Dimarogona, Maria
    Department of Chemical Engineering, University of Patras, Patras, Greece.
    Karagiannaki, Ioanna
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, Athens, Greece.
    Chalima, Angelina
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, Athens, Greece.
    Fishman, Ayelet
    Department of Biotechnology and Food Engineering, Technion-Israel Institute of Technology, Haifa, Israel.
    Topakas, Evangelos
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, Athens, Greece.
    Characterization and protein engineering of a novel versatile fungal polyphenol oxidase with chlorophenol bioremediation potential2018Inngår i: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Polyphenol oxidases (PPOs) have been mostly associated with the undesirable post-harvest browning in fruits and vegetables and with implications in human melanogenesis. Nonetheless, they are considered useful biocatalysts in the food, pharmaceutical and cosmetic industries. The aim of the present work was to characterize a novel PPO and explore its potential as a bioremediation agent. A gene encoding an extracellular tyrosinase-like enzyme was amplified from the genome of Thermothelomyces thermophila and expressed in Pichia pastoris. The recombinant enzyme (TtPPO) was purified and biochemically characterized. Its production reached 40 mg/L and it appeared to be a glycosylated and N-terminally processed protein. TtPPO showed broad substrate specificity as it could oxidize 28/30 compounds tested, including polyphenols, substituted phenols, catechols and methoxyphenols. Its optimum temperature was 65 °C with a half-life of 18.3 h at 50 °C, while its optimum pH was 7.5. The homology model of TtPPO was constructed and site-directed mutagenesis was performed in order to increase its activity on mono- and di-chlorophenols (CPs). TtPPO variant G292N/Y296V had a 5.3-fold increased activity on 3,5-diCP compared to wild-type.

    Importance A novel fungal PPO was heterologously expressed and biochemically characterized. Construction of single and double mutants led to the generation of variants with altered specificity against CPs. Through this work, knowledge is gained regarding the effect of mutations on the substrate specificity of PPOs. This work also demonstrates that more potent biocatalysts for the bioremediation of harmful CPs can be developed by applying site-directed mutagenesis.

  • 231.
    Nilsson, Oskar
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Optimization of Single Cell Protein production from spent silfite liquor using Paecilomyces variotii2017Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Fish has for a long time been a very important source of protein for human kind and with the world population at an all-time high, 7.5 billion and rapidly growing, the demand for fish as a food source is also at an all-time high and rapidly increasing. This has in turn led to overexploitation of many of the fish stocks of the world ocean’s and in many cases to depletion of fish stocks. The demand for sustainable food sources and sustainable usage of the world ocean’s fish stocks is therefore a subject with great deal of interest today. Much of the fish caught today are used for production of fish meal for usage as fish food at fish farms, which also increases the depletion of fish stocks around the globe.

    One way of dealing with this problem is to replace the fish meal as protein source in fish feed with protein from agricultural crops which in many cases are done today by usage of soy bean protein. This however poses another problem as the agricultural crops take up vast amount of land, in many cases obtained by diminishing the rainforests in the area. Another usage for the soybean would be as a direct human food source. Agricultural products are also dependent on environmental conditions to ensure reasonable production. The problems related to production of fish meal and soy has sparked the idea of using microorganisms for production of Single cell protein for usage as protein source in fish feed. Single cell protein can be produced in closed fermentation vessels and can be produced at a controlled rate and under controlled manners, while taking up negligible land space.

    During this thesis, the production of single cell protein from spent sulfite liquor using the filamentous fungi Paecilomyces variotii was examined. The aim of the project was to examine the effect of cultivation parameters (i.e., pH, temperature and nutrients) on the production of biomass as well as the protein content of the biomass. The correlation of the biomass growth and protein content have also been examined.

    The project was carried out by performing several experiment cultivations using spent sulfite liquor provided by Domsjö Fabriker in Örnsköldsvik. This process enables the utilization of a residual stream from the pulp industry which gives this process a huge environmental upside compared to similar processes as for example the commercial production of Quorn (a Single cell based food product) which utilizes pure glucose.

    The results showed that the protein content will steadily decrease as the biomass production increases hence it is desirable to keep the cultivation time at a minimum while maximizing biomass production during that time frame. It also points towards that the highest protein content is present in the young cell mass.

    The key conclusion from this thesis is however that it is possible to lower the pH of the cultivation from pH 6 down to pH 4.5 while still maintaining the biomass production and increasing the protein content. The highest obtained protein content was 62.7% at pH 4.5. The high protein content might be due to a slightly longer lag phase in the beginning of the cultivation which yields a higher number of younger cells in the final broth thus increasing protein content. Running the process at a lower pH is a huge advantage for industrial implementation as this on large scale means significant lower amounts of chemicals needed for pH adjusting of the spent sulfite liquor which renders the process much more economical. This is because pH adjustment today is one of the most costly process steps in the production of bioethanol from spent sulfite liquor. 

  • 232.
    Nilsson, Robert
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Bauer, Fredric
    Chemical Engineering, Lund University.
    Mesfun, Sennai
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Hulteberg, Christian
    Chemical Engineering, Lund University.
    Lundgren, Joakim
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Wännström, Sune
    SP Technical Research Institute of Sweden.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Berglund, Kris
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Techno-economics of carbon preserving butanol production using a combined fermentative and catalytic approach2014Inngår i: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 161, s. 263-269Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents a novel process for n-butanol production which combines a fermentation consuming carbon dioxide (succinic acid fermentation) with subsequent catalytic reduction steps to add hydrogen to form butanol. Process simulations in Aspen Plus have been the basis for the techno-economic analyses performed. The overall economy for the novel process cannot be justified, as production of succinic acid by fermentation is too costly. Though, succinic acid price is expected to drop drastically in a near future. By fully integrating the succinic acid fermentation with the catalytic conversion the need for costly recovery operations could be reduced. The hybrid process would need 22% less raw material than the butanol fermentation at a succinic acid fermentation yield of 0.7 g/g substrate. Additionally, a carbon dioxide fixation of up to 13 ktonnes could be achieved at a plant with an annual butanol production of 10 ktonnes

  • 233.
    Nitsos, Christos
    et al.
    Laboratory of General and Inorganic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki.
    Matis, Konstantinos A.
    Laboratory of General and Inorganic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki.
    Triantafyllidis, Kostas
    Laboratory of General and Inorganic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, Chemical Process and Energy Resources Institute, Centre for Research and Technology-Hellas (CPERI/CERTH), 57001 Thessaloniki, Greece.
    Optimization of hydrothermal pretreatment of lignocellulosic biomass in the bioethanol production process2013Inngår i: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 6, nr 1, s. 110-122Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The natural resistance to enzymatic deconstruction exhibited by lignocellulosic materials has designated pretreatment as a key step in the biological conversion of biomass to ethanol. Hydrothermal pretreatment in pure water represents a challenging approach because it is a method with low operational costs and does not involve the use of organic solvents, difficult to handle chemicals, and "external" liquid or solid catalysts. In the present work, a systematic study has been performed to optimize the hydrothermal treatment of lignocellulosic biomass (beech wood) with the aim of maximizing the enzymatic digestibility of cellulose in the treated solids and obtaining a liquid side product that could also be utilized for the production of ethanol or valuable chemicals. Hydrothermal treatment experiments were conducted in a batch-mode, high-pressure reactor under autogeneous pressure at varying temperature (130-220 °C) and time (15-180 min) regimes, and at a liquid-to-solid ratio (LSR) of 15. The intensification of the process was expressed by the severity factor, log Ro. The major changes induced in the solid biomass were the dissolution/removal of hemicellulose to the process liquid and the partial removal and relocation of lignin on the external surface of biomass particles in the form of recondensed droplets. The above structural changes led to a 2.5-fold increase in surface area and total pore volume of the pretreated biomass solids. The enzymatic hydrolysis of cellulose to glucose increased from less than 7 wt % for the parent biomass to as high as 70 wt % for the treated solids. Maximum xylan recovery (60 wt %) in the hydrothermal process liquid was observed at about 80 wt % hemicellulose removal; this was accomplished by moderate treatment severities (log R o=3.8-4.1). At higher severities (log Ro=4.7), xylose degradation products, mainly furfural and formic acid, were the predominant chemicals formed. Green fuels and chemicals: The enzymatic digestibility of cellulose in lignocellulosic biomass towards fermentable glucose can be increased significantly by hydrothermal pretreatment in pure water under relatively mild conditions. Appropriate selection of the pretreatment temperature and time also leads to a process liquid that can be enriched in xylose or in furfural and acetic acid

  • 234.
    Nitsos, Christos
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Matsakas, Leonidas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Triantafyllidis, Kostas
    Chemical Process and Energy Resources Institute, Centre for Research and Technology-Hellas (CPERI/CERTH), 57001 Thessaloniki, Greece, Laboratory of General and Inorganic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, 54124 Thessaloniki.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Evaluation of Mediterranean Agricultural Residues as a Potential Feedstock for the Production of Biogas via Anaerobic Fermentation2015Inngår i: BioMed Research International, ISSN 2314-6133, E-ISSN 2314-6141, Vol. 2015, artikkel-id 171635Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hydrothermal, dilute acid, and steam explosion pretreatment methods, were evaluated for their efficiency to improve the methane production yield of three Mediterranean agricultural lignocellulosic residues such as olive tree pruning, grapevine pruning, and almond shells. Hydrothermal and dilute acid pretreatments provided low to moderate increase in the digestibility of the biomass samples, whereas steam explosion enabled the highest methane yields to be achieved for almond shells at 232.2 ± 13.0 mL CH4/gVS and olive pruning at 315.4 ± 0.0 mL CH4/gVS. Introduction of an enzymatic prehydrolysis step moderately improved methane yields for hydrothermal and dilute acid pretreated samples but not for the steam exploded ones.

  • 235.
    Nitsos, Christos
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Laboratory of General and Inorganic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki.
    Matsakas, Leonidas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Triantafyllidis, Kostas
    Laboratory of General and Inorganic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki; Chemical Process and Energy Resources Institute, Centre for Research and Technology-Hellas (CPERI/CERTH).
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Investigation of different pretreatment methods of Mediterranean-type ecosystem agricultural residues: characterisation of pretreatment products, high-solids enzymatic hydrolysis and bioethanol production2017Inngår i: Biofuels, ISSN 1759-7269, E-ISSN 1759-7277Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Agricultural and agro-industrial lignocellulosic residues represent an important renewable resource for the production of fuels and chemicals towards a bio-based economy. Olive pruning, vineyard pruning and almond shells are important residues from agricultural activities in Mediterranean-type ecosystems. In the current work, bioethanol production from the above three types of agro-residues was studied, focusing on the effect of different pretreatment methods on enzymatic saccharrification efficiency of cellulose and production of second-generation bioethanol. Dilute acid, hydrothermal and steam explosion pretreatments were compared in order to remove hemicellulose and facilitate the subsequent enzymatic hydrolysis of the hemicellulose-deficient biomass to glucose. Enzymatic hydrolysis was performed in a free-fall mixing reactor enabling high solids loading of 23% w/w. This allowed hydrolysis of up to 67% of available cellulose in almond shells and close to 50% in olive pruning samples, and facilitated high ethanol production in the subsequent fermentation step; the highest ethanol concentrations achieved were 47.8 g/L for almond shells after steam explosion and 42 g/L for hydrothermally pretreated olive pruning residue.

  • 236.
    Nitsos, Christos
    et al.
    Laboratory of General and Inorganic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki.
    Mihailof, Chrysa M.
    Chemical Process and Energy Resources Institute, Centre for Research and Technology-Hellas (CPERI/CERTH), 57001 Thessaloniki, Greece.
    Matis, Konstantinos A.
    Laboratory of General and Inorganic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki.
    Lappas, Angelos A
    Chemical Process and Energy Resources Institute, Centre for Research and Technology-Hellas (CPERI/CERTH), 57001 Thessaloniki, Greece.
    Triantafyllidis, Kostas
    Laboratory of General and Inorganic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, Chemical Process and Energy Resources Institute, Centre for Research and Technology-Hellas (CPERI/CERTH), 57001 Thessaloniki, Greece.
    The Role of Catalytic Pretreatment in Biomass Valorization Toward Fuels and Chemicals2013Inngår i: The Role of Catalysis for the Sustainable Production of Bio-fuels and Bio-chemicals, Elsevier, 2013, s. 217-260Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    The enzymatic hydrolysis of cellulose toward fermentable glucose is of paramount importance for the production of ethanol or other high-value chemicals from lignocellulosic biomass via the biochemical route. A pretreatment step is usually required that alters the structure and composition of biomass, reduces its recalcitrance, and allows the efficient enzymatic conversion of carbohydrates into sugars. Biomass pretreatment aims mainly at the selective separation of hemicellulose and/or lignin, either as oligomers or as smaller sugar and phenolic molecules, which can be further converted enzymatically or via chemical catalysis to platform chemicals or fuel precursors. In this chapter, a review of the most widely applied pretreatment methods is presented, with the aim of elucidating the role of chemical or biochemical catalysis in this first step of biomass valorization

  • 237.
    Nitsos, Christos
    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.
    Organosolv fractionation of softwood biomass for biofuel and biorefinery applications2018Inngår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 11, nr 1, artikkel-id 50Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Softwoods represent a significant fraction of the available lignocellulosic biomass for conversion into a variety of bio-based products. Its inherent recalcitrance, however, makes its successful utilization an ongoing challenge. In the current work the research efforts for the fractionation and utilization of softwood biomass with the organosolv process are reviewed. A short introduction into the specific challenges of softwood utilization, the development of the biorefinery concept, as well as the initial efforts for the development of organosolv as a pulping method is also provided for better understanding of the related research framework. The effect of organosolv pretreatment at various conditions, in the fractionation efficiency of wood components, enzymatic hydrolysis and bioethanol production yields is then discussed. Specific attention is given in the effect of the pretreated biomass properties such as residual lignin on enzymatic hydrolysis. Finally, the valorization of organosolv lignin via the production of biofuels, chemicals, and materials is also described. 

  • 238.
    Nitsos, Christos
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Stoklosa, Ryan J.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI.
    Karnaouri, Anthi C
    Department of Chemical Sciences and Technologies, Via della Ricerca Scientifica, University of Rome Tor Vergata.
    Vörös, Dimitrij
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Lange, Heikko
    Department of Chemical Sciences and Technologies, Via della Ricerca Scientifica, University of Rome Tor Vergata.
    Hodge, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Crestini, Claudia
    Department of Chemical Sciences and Technologies, Via della Ricerca Scientifica, University of Rome Tor Vergata.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Isolation and Characterization of Organosolv and Alkaline Lignins from Hardwood and Softwood Biomass2016Inngår i: ACS Sustainable Chemistry and Engineering, ISSN 2168-0485, Vol. 4, nr 10, s. 5181-5193Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Isolation of lignins from hardwood and softwood biomass samples, containing 26.1% and 28.1% lignin, respectively, has been performed with the use of alkaline and organosolv pretreatment methods. The effect of catalyst loading, ethanol content, particle size, and pretreatment time on the yields and properties of the isolated lignins were investigated. Alkaline lignins had higher carbohydrate content - up to 30% - and exhibited higher molecular weights in the range of 3000 Da, with a maximum phenolic hydroxyl content of 1 mmol g-1 for birch and 2 mmol g-1 for spruce. Organosolv lignins, on the other hand, showed high purity - 93% or higher - despite the more extensive biomass dissolution into the pretreatment medium; they also exhibited a lower range of molecular weights between 600 and 1600 Da depending on the source and pretreatment conditions. Due to the lower molecular weight, phenolic hydroxyl content was also increased, reaching as high as 4 mmol g-1 with a simultaneous decrease in aliphatic hydroxyl content as low as 0.6 mmol g-1. Efficient lignin dissolution of 62% for spruce and 69% for birch, achieved at optimal pretreatment conditions, was combined with extensive hemicellulose removal

  • 239. Nordgren, Daniel
    et al.
    Hedman, Henry
    Padban, Nader
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik, Energiteknik och termisk processkemi.
    Öhman, Marcus
    Ash transformations in pulverised fuel co-combustion of straw and woody biomass2013Inngår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 105, s. 52-58Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ash transformation processes have been studied during co-firing of wheat straw and pine stem wood and softwood bark. Pilot-scale trials in a 150 kW pulverised-fuel-fired burner were performed. Thermodynamic equilibrium calculations were made to support the interpretation of the results. The results show that reactions involving condensed phases are kinetically limited compared to reactions between gaseous ash compounds. Accordingly, the conditions promote gas phase reactions resulting in the formation of chlorides, sulphates and carbonates whereas reactions involving condensed reactants are suppressed. Both the slagging and fouling propensities of all co-firing mixes were reduced compared to that for pure straw. For the wood/straw mixes this was mainly due to a dilution of the ash forming elements of straw whereas for straw/bark, an additional effect from interaction between the fuel ash components was observed to reduce slagging. In general it can be concluded that under powder combustion conditions equilibrium is approached selectively and that the ash matter is strongly fractionated. The general results in this paper are useful for straw-fired power stations looking for alternative co-firing fuels.

  • 240.
    Nordlander, Eva
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik.
    Thorin, Eva
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik.
    Yan, Jinyue
    KTH.
    Modeling of a full-scale biogas plant using a dynamic neural network2013Konferansepaper (Fagfellevurdert)
  • 241.
    Nylander, Filip
    et al.
    Chalmers University of Technology, Department of Chemistry and Chemical Enginering.
    Sunner, Hampus
    Chalmers University of Technology, Department of Chemical and Biological Engineering.
    Olsson, Lisbeth
    Chalmers University of Technology, Department of Chemical and Biological Engineering.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Westman, Gunnar
    Chalmers University of Technology, Department of Chemistry and Chemical Enginering.
    Synthesis and enzymatic hydrolysis of a diaryl benzyl ester model of a lignin-carbohydrate complex (LCC)2016Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 70, nr 5, s. 385-391Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Specific degradation of the bonds between lignin and carbohydrates is an important step towards separating individual lignocellulosic biopolymers for sustainable production of materials and chemicals. One of the most established covalent lignin-carbohydrate (LC) interactions is the ester bond between the α- or γ-hydroxyl group of a lignin phenylpropane unit and a glucuronic acid side chain of xylan. In this work, a model of the LC benzyl ester bond was synthesized in a one-pot reaction from a β-O-4 lignin unit and d-glucuronic acid, both from commercial sources. The resulting lignin-carbohydrate complex (LCC) model was unstable in aqueous solution. However, at pH 4, the rate of spontaneous hydrolysis was sufficiently low to allow for enzymatic splitting experiments. The enzymatic hydrolysis of the LC benzyl ester bond of the LCC model was demonstrated by means of the glucuronoyl esterase StGE2 from Sporotrichum thermophile, which showed a preference for erythro forms of the LCC model

  • 242.
    Ofoli, R.
    et al.
    Michigan State University.
    Komolprasert, V.
    Michigan State University.
    Saha, B.C.
    Michigan State University.
    Berglund, Kris
    Extrusion liquefaction and saccharification of carbohydrate substrates1990Inngår i: Food biotechnology, ISSN 0890-5436, E-ISSN 1532-4249, Vol. 4, nr 1, s. 365-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The objective of this study was to assess the feasibility of accomplishing enzymatic liquefaction and saccharification of carbohydrate formulations during one pass in a twin-screw food extruder. The combined liquefaction and saccharification process was carried out on a cereal grain formulation in a pilot-scale twin screw Baker Perkins extruder, using thermophilic α- and β-amylase. The biggest limitation on the process was the short residence times characteristic of the extruder. This problem was partially overcome by a combination of screw configurations, mass flow rates and RPM which extended the residence times and enhanced the extent of reaction. Results indicate that this type of technology may provide some opportunities for the food and biochemical industry.

  • 243.
    Olofsson, Martin
    et al.
    Linnéuniversitetet, Fakulteten för Hälso- och livsvetenskap (FHL), Institutionen för biologi och miljö (BOM).
    Lamela, Teresa
    Necton SA, Olhao, Portugal.
    Nilsson, Emmelie
    Linnéuniversitetet, Fakulteten för Hälso- och livsvetenskap (FHL), Institutionen för biologi och miljö (BOM).
    Bergé, Jean-Pascal
    IFREMER, Nantes, France.
    del Pino, Victória
    Necton SA, Olhao, Portugal.
    Uronen, Pauliina
    Neste Oil, Ctr Technol, Porvoo, Finland.
    Legrand, Catherine
    Linnéuniversitetet, Fakulteten för Hälso- och livsvetenskap (FHL), Institutionen för biologi och miljö (BOM).
    Combined Effects of Nitrogen Concentration and Seasonal Changes on the Production of Lipids in Nannochloropsis oculata 2014Inngår i: Marine Drugs, ISSN 1660-3397, E-ISSN 1660-3397, Vol. 12, nr 4, s. 1891-1910Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Instead of sole nutrient starvation to boost algal lipid production, we addressed nutrient limitation at two different seasons (autumn and spring) during outdoor cultivation in flat panel photobioreactors. Lipid accumulation, biomass and lipid productivity and changes in fatty acid composition of Nannochloropsis oculata were investigated under nitrogen (N) limitation (nitrate:phosphate N:P 5, N:P 2.5 molar ratio). N. oculata was able to maintain a high biomass productivity under N-limitation compared to N-sufficiency (N:P 20) at both seasons, which in spring resulted in nearly double lipid productivity under N-limited conditions (0.21 g L−1 day−1) compared to N-sufficiency (0.11 g L−1 day−1). Saturated and monounsaturated fatty acids increased from 76% to nearly 90% of total fatty acids in N-limited cultures. Higher biomass and lipid productivity in spring could, partly, be explained by higher irradiance, partly by greater harvesting rate (~30%). Our results indicate the potential for the production of algal high value products (i.e., polyunsaturated fatty acids) during both N-sufficiency and N-limitation. To meet the sustainability challenges of algal biomass production, we propose a dual-system process: Closed photobioreactors producing biomass for high value products and inoculum for larger raceway ponds recycling waste/exhaust streams to produce bulk chemicals for fuel, feed and industrial material.

  • 244.
    Olofsson, Martin
    et al.
    Linnéuniversitetet, Institutionen för biologi och miljö (BOM).
    Lamela, Teresa
    Necton SA, Olhao, Portugal.
    Nilsson, Emmelie
    Linnéuniversitetet, Institutionen för biologi och miljö (BOM).
    Bergé, Jean-Pascal
    IFREMER, Nantes, France.
    del Pino, Victória
    Necton SA, Olhao, Portugal.
    Uronen, Pauliina
    Neste Oil, Ctr Technol, Porvoo, Finland.
    Legrand, Catherine
    Linnéuniversitetet, Institutionen för biologi och miljö (BOM).
    Combined Effects of Nitrogen Concentration and Seasonal Changes on the Production of Lipids in Nannochloropsis oculata 2014Inngår i: Marine Drugs, ISSN 1660-3397, E-ISSN 1660-3397, Vol. 12, nr 4, s. 1891-1910Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Instead of sole nutrient starvation to boost algal lipid production, we addressed nutrient limitation at two different seasons (autumn and spring) during outdoor cultivation in flat panel photobioreactors. Lipid accumulation, biomass and lipid productivity and changes in fatty acid composition of Nannochloropsis oculata were investigated under nitrogen (N) limitation (nitrate:phosphate N:P 5, N:P 2.5 molar ratio). N. oculata was able to maintain a high biomass productivity under N-limitation compared to N-sufficiency (N:P 20) at both seasons, which in spring resulted in nearly double lipid productivity under N-limited conditions (0.21 g L−1 day−1) compared to N-sufficiency (0.11 g L−1 day−1). Saturated and monounsaturated fatty acids increased from 76% to nearly 90% of total fatty acids in N-limited cultures. Higher biomass and lipid productivity in spring could, partly, be explained by higher irradiance, partly by greater harvesting rate (~30%). Our results indicate the potential for the production of algal high value products (i.e., polyunsaturated fatty acids) during both N-sufficiency and N-limitation. To meet the sustainability challenges of algal biomass production, we propose a dual-system process: Closed photobioreactors producing biomass for high value products and inoculum for larger raceway ponds recycling waste/exhaust streams to produce bulk chemicals for fuel, feed and industrial material.

  • 245.
    Olsson, Carina
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea IVF AB.
    Sjöholm, Elisabeth
    RISE - Research Institutes of Sweden, Bioekonomi. RISE., Innventia.
    Reimann, Anders
    RISE - Research Institutes of Sweden, Bioekonomi. RISE., Innventia.
    Carbon fibres from precursors produced by dry-jet wet-spinning of kraft lignin blended with kraft pulps2017Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 71, nr 4, s. 275-283Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A part of kraft lignin (KL) can be used as a value-added product without detracting the chemical recovery and the energy balance of the kraft mill. The focus of this study is the production of light-weight carbon fibres (CFS) from KL obtained by the LignoBoost process. For this purpose, crude KL and various cellulose products from kraft pulping of hardwood (HW) and softwood (SW) were dissolved in 1-ethyl-3-methylimidazolium acetate ([EMIm][OAc]) and submitted to dry-jet wet-spun to obtain precursor fibres containing 70% KL and 30% cellulose, which were thermally stabilised and further converted by thermal treatments into CF. The initial and final products were characterised with respect to, e.g. mole mass distribution, thermal properties, tensile strength and tensile modulus determination. The optimised precursor fibres are smooth and flexible with similar mechanical properties as commercial textile fibres. The best CFS made had a tensile strength of 780 MPa and a tensile modulus of 68 GPa and are thus stronger and stiffer than those produced by melt-spinning of SW-based lignins alone. The new CFS based on dry-jet wet-spun precursors still have a high potential for further improvements.

  • 246.
    Pan, Borlan
    et al.
    Michigan State University.
    Berglund, Kris
    Time-resolved fluorescence and anisotropy of covalently coupled 1-pyrenebutyric acid for monitoring the crystallization conditions of lysozyme1997Inngår i: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 171, nr 1-2, s. 226-235Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Time-resolved fluorescence and anisotropy measurements of trace amounts of 1-pyrenebutyric acid labeled hen egg-white lysozyme (PBA-HEL) were used to characterize hen egg-white lysozyme (HEL) crystallization conditions. The effects of sodium chloride and protein concentrations on the fluorescence lifetimes and rotational correlation times of the labeled protein were examined. These results were compared with the effects of the salts ammonium acetate and ammonium sulfate. Addition of protein precipitants caused increases in the rotational correlation times which were attributed to a combination of steric, hydrodynamic, general electrostatic and specific ionic interactions. This decrease in the rotational mobility of HEL appears to be a necessary but not sufficient condition to allow the formation of specific interactions leading to crystallization. The results demonstrated that fluorescence measurements are effective in characterizing and monitoring protein crystallization processes prior to the appearance of macroscopic crystals.

  • 247.
    Pan, Borlan
    et al.
    Michigan State University.
    Chakraborty, Reena
    Michigan State University.
    Berglund, Kris
    Time resolved fluorescence and anisotropy of 1-pyrene butyric acid and pyranine as probes of solvent organization in sucrose solutions1993Inngår i: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 130, nr 3-4, s. 587-599Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The microenvironment of solute-solvent interactions in aqueous sucrose solutions, ranging from 0 to 80 wt% in concentration, was investigated using time resolved fluorescence techniques. The fluorescence lifetimes and rotational correlation times of the trace fluorescent probes, PBA (1-pyrene butyric acid) and pyranine (trisodium 8-hydroxy-1,3,6-pyrenetrisulfonate), were measured in sucrose solutions. The behavior of the fluorescence lifetimes and the increase in the rotational correlation times with increasing sucrose concentration provided no evidence for the formation of water exclusive solute clusters in the metastable solutions. Instead, the results indicated the formation of a network of hydrogen bonding interactions between dispersed sucrose molecules.

  • 248. Papapetridis, Ioannis
    et al.
    van Dijk, Marlous
    van Maris, Antonius J. A.
    KTH, Skolan för bioteknologi (BIO), Industriell bioteknologi. Delft University Technology, Netherlands.
    Pronk, Jack T.
    Metabolic engineering strategies for optimizing acetate reduction, ethanol yield and osmotolerance in Saccharomyces cerevisiae2017Inngår i: Biotechnology for Biofuels, ISSN 1754-6834, E-ISSN 1754-6834, Vol. 10, nr 1, artikkel-id 107Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: Glycerol, whose formation contributes to cellular redox balancing and osmoregulation in Saccharomyces cerevisiae, is an important by-product of yeast-based bioethanol production. Replacing the glycerol pathway by an engineered pathway for NAD(+)-dependent acetate reduction has been shown to improve ethanol yields and contribute to detoxification of acetate-containing media. However, the osmosensitivity of glycerol non-producing strains limits their applicability in high-osmolarity industrial processes. This study explores engineering strategies for minimizing glycerol production by acetate-reducing strains, while retaining osmotolerance. Results: GPD2 encodes one of two S. cerevisiae isoenzymes of NAD(+)-dependent glycerol-3-phosphate dehydrogenase (G3PDH). Its deletion in an acetate-reducing strain yielded a fourfold lower glycerol production in anaerobic, low-osmolarity cultures but hardly affected glycerol production at high osmolarity. Replacement of both native G3PDHs by an archaeal NADP(+)-preferring enzyme, combined with deletion of ALD6, yielded an acetate-reducing strain the phenotype of which resembled that of a glycerol-negative gpd1 Delta gpd2 Delta strain in low-osmolarity cultures. This strain grew anaerobically at high osmolarity (1 mol L-1 glucose), while consuming acetate and producing virtually no extracellular glycerol. Its ethanol yield in high-osmolarity cultures was 13% higher than that of an acetate-reducing strain expressing the native glycerol pathway. Conclusions: Deletion of GPD2 provides an attractive strategy for improving product yields of acetate-reducing S. cerevisiae strains in low, but not in high-osmolarity media. Replacement of the native yeast G3PDHs by a heterologous NADP(+)-preferring enzyme, combined with deletion of ALD6, virtually eliminated glycerol production in high-osmolarity cultures while enabling efficient reduction of acetate to ethanol. After further optimization of growth kinetics, this strategy for uncoupling the roles of glycerol formation in redox homeostasis and osmotolerance can be applicable for improving performance of industrial strains in high-gravity acetate-containing processes.

  • 249.
    Papaspyrid, L. -M.
    et al.
    National Technical University of Athens.
    Sbokov, E.
    National Technical University of Athens.
    Christakopoulos, Paul
    Effect of carbon and nitrogen sources on the production of dietary fibres and glucans by submerged cultures of two greek mushroom species, Ganoderma australe and Pleurotus ostreatus2012Inngår i: Acta alimentaria, ISSN 0139-3006, E-ISSN 1588-2535, Vol. 41, nr 2, s. 200-210Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study was aimed to investigate the effect of carbon and nitrogen sources on the production of bioactive total dietary fibres (TDF) and glucans (α- and β-glucans) in submerged cultures of wild Ganoderma australe and commercial Pleurotus ostreatus, both of Greek origin. The contents of glucans and TDF were determined by using the respective Megazyme enzymatic kits. Glucose and yeast extract (YE) were suggested as appropriate carbon and nitrogen sources, respectively, for obtaining simultaneously high production of TDF and β-glucans by G. australe, which are compounds of great pharmacological interest, whereas maltose and YE were found favourable for high production of the above-mentioned functional components by P. ostreatus. The data obtained in this study provide useful information for further development of the studied mushroom fermentation process on a scale of the bioreactor aiming at enhanced TDF and β-glucan production.

  • 250.
    Papaspyridi, Lefki Maria
    et al.
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Zerva, Anastasia
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Topakas, Evangelos
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Biocatalytic synthesis of fungal β-glucans2018Inngår i: Catalysts, ISSN 2073-4344, Vol. 8, nr 7, artikkel-id 274Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Glucans are the dominant polysaccharide constituents of fungal cell walls. Remarkably, these major bioactive polysaccharides account for the beneficial effects that have been observed by many mushrooms of medicinal interest. Accordingly, the prevailing tendency is the use of bioactive mushroom β-glucans mainly in pharmaceutical industries or as food additives, since it seems that they can be involved in meeting the overall growing demand for food in the future, but also in medical and material sectors. β-(1,3)-Glucan synthase (GLS) is the responsible enzyme for the synthesis of these important polysaccharides, which is a member of the glycosyl transferase (GT) family. For optimizing the production of such natural polymers of great interest, the comprehension of the fungal synthetic mechanism, as well as the biochemical and molecular characteristics of the key enzyme GLS and its expression seem to be crucial. Overall, in this review article, the fungal β-glucans biosynthesis by GLS is summarized, while the in vitro synthesis of major polysaccharides is also discussed, catalyzed by glycoside hydrolases (GHs) and GTs. Possible future prospects of GLS in medicine and in developing other potential artificial composite materials with industrial applications are also summarized

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