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  • 1. Alriksson, Björn
    Ethanol from lignocellulose: Alkali detoxification of dilute-acid spruce hydrolysates2006Licentiate thesis, monograph (Other academic)
  • 2.
    Alriksson, Björn
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Ethanol from lignocellulose: Alkali detoxification of dilute-acid spruce hydrolysates2006Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Detoxification of dilute-acid lignocellulose hydrolysates by treatment with Ca(OH)2 (overliming) efficiently improves the production of fuel ethanol, but is associated with drawbacks like sugar degradation and CaSO4 precipitation. In factorial designed experiments, in which pH and temperature were varied, dilute-acid spruce hydrolysates were treated with Ca(OH)2, NH4OH or NaOH. The concentrations of sugars and inhibitory compounds were measured before and after the treatments. The fermentability was examined using the yeast Saccharomyces cerevisiae and compared with reference fermentations of synthetic medium without inhibitors. The treatment conditions were evaluated by comparing the balanced ethanol yield, which takes both the degradation of sugars and the ethanol production into account. Treatment conditions resulting in excellent fermentability and minimal sugar degradation were possible to find regardless of whether Ca(OH)2, NH4OH or NaOH was used. Balanced ethanol yields higher than those of the reference fermentations were achieved for hydrolysates treated with all three types of alkali. As expected, treatment with Ca(OH)2 gave rise to precipitated CaSO4. The NH4OH treatments gave rise to a brownish precipitate but the amounts of precipitate formed were relatively small. No precipitate was observed in treatments with NaOH. The possibility that the ammonium ions from the NH4OH treatments gave a positive effect as an extra source of nitrogen during the fermentations was excluded after experiments in which NH4Cl was added to the medium. The findings presented can be used to improve the effectiveness of alkali detoxification of lignocellulose hydrolysates and to minimize problems with sugar degradation and formation of precipitates.

  • 3.
    Alriksson, Björn
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Ethanol from lignocellulose: Management of by-products of hydrolysis2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Fuel ethanol can be produced from lignocellulosic materials, such as residues from agriculture and forestry. The polysaccharides of lignocellulose are converted to sugars by hydrolysis and the sugars can then be fermented to ethanol using microorganisms. However, during hydrolysis a wide range of by-products are also generated. By-product formation can affect ethanol yield and productivity. Management of by-products of hydrolysis is therefore important in the development of commercially viable production of cellulosic ethanol.

    Detoxification of inhibitory dilute-acid lignocellulose hydrolysates by treatment with Ca(OH)2 (overliming) efficiently improves the fermentability, but is associated with drawbacks like sugar degradation and CaSO4 precipitation. In factorial designed experiments, in which pH and temperature were varied, dilute-acid spruce hydrolysates were treated with Ca(OH)2, NH4OH or NaOH. The concentrations of sugars and inhibitory compounds were measured before and after the treatments. The fermentability was examined using the yeast Saccharomyces cerevisiae and compared with reference fermentations of synthetic medium without inhibitors. The treatment conditions were evaluated by comparing the balanced ethanol yield, which takes both the degradation of sugars and the ethanol production into account. Treatment conditions resulting in excellent fermentability and minimal sugar degradation were possible to find regardless of whether Ca(OH)2, NH4OH or NaOH was used. Balanced ethanol yields higher than those of the reference fermentations were achieved for hydrolysates treated with all three types of alkali. As expected, treatment with Ca(OH)2 gave rise to precipitated CaSO4. The NH4OH treatments gave rise to a brownish precipitate but the amounts of precipitate formed were relatively small. No precipitate was observed in treatments with NaOH. The findings presented can be used to improve the effectiveness of alkali detoxification of lignocellulose hydrolysates and to minimize problems with sugar degradation and formation of precipitates.

    Overexpression of different S. cerevisiae genes was investigated with the aim to engineer a biocatalyst with increased inhibitor tolerance. Overexpression of YAP1, a gene encoding a transcription factor, conveyed increased resistance to lignocellulose-derived inhibitors as well as to a dilute-acid hydrolysate of spruce.

    Recombinant Aspergillus niger expressing the Hypocrea jecorina endoglucanase Cel7B was cultivated on spent lignocellulose hydrolysate (stillage). The fungus simultaneously removed inhibitors present in the stillage and produced higher amounts of endoglucanase than when it was grown in a standard medium with comparable monosaccharide content. The concept can be applied for on-site production of enzymes in a cellulose-to-ethanol process and facilitate recycling of the stillage stream.

  • 4.
    Alriksson, Björn
    et al.
    Karlstad University, Division for Chemistry.
    Horváth, Ilona Sárvári
    Karlstad University, Division for Chemistry.
    Sjöde, Anders
    Karlstad University, Division for Chemistry.
    Nilvebrant, Nils-Olof
    Karlstad University, Division for Chemistry.
    Jönsson, Leif J
    Karlstad University, Division for Chemistry.
    Ammonium hydroxide detoxification of spruce acid hydrolysates.2005In: Applied Biochemistry and Biotechnology, ISSN 0273-2289, E-ISSN 1559-0291, Vol. 121-124, p. 911-22Article in journal (Refereed)
    Abstract [en]

    When dilute-acid hydrolysates from spruce are fermented to produce ethanol, detoxification is required to make the hydrolysates fermentable at reasonable rates. Treatment with alkali, usually by overliming, is one of the most efficient approaches. Several nutrients, such as ammonium and phosphate, are added to the hydrolysates prior to fermentation. We investigated the use of NH4OH for simultaneous detoxification and addition of nitrogen source. Treatment with NH4OH compared favorably with Ca(OH)2, Mg(OH)2, Ba(OH)2, and NaOH to improve fermentability using Saccharomyces cerevisiae. Analysis of monosaccharides, furan aldehydes, phenols, and aliphatic acids was performed after the different treatments. The NH4OH treatments, performed at pH 10.0, resulted in a substantial decrease in the concentrations of furfural and hydroxymethylfurfural. Under the conditions studied, NH4OH treatments gave better results than Ca(OH)2 treatments. The addition of an extra nitrogen source in the form of NH4Cl at pH 5.5 did not result in any improvement in fermentability that was comparable to NH4OH treatments at alkaline conditions. The addition of CaCl2 or NH4Cl at pH 5.5 after treatment with NH4OH or Ca(OH)2 resulted in poorer fermentability, and the negative effects were attributed to salt stress. The results strongly suggest that the highly positive effects of NH4OH treatments are owing to chemical conversions rather than stimulation of the yeast cells by ammonium ions during the fermentation.

  • 5.
    Alriksson, Björn
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Rose, Shaunita, H
    Department of Microbiology, University of Stellenbosch, South Africa.
    van Zyl, Wilhelm, H
    Department of Microbiology, University of Stellenbosch, South Africa.
    Sjöde, Anders
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Nilvebrant, Nils-Olof
    STFI-Packforsk AB, Stockholm, Sweden.
    Jönsson, Leif J.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Cellulase Production from Spent Lignocellulose Hydrolysates with Recombinant Aspergillus niger.2009In: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 75, no 8, p. 2366-2374Article in journal (Refereed)
  • 6.
    Alriksson, Björn
    et al.
    Karlstad University, Faculty of Technology and Science.
    Sjöde, Anders
    Karlstad University, Faculty of Technology and Science.
    Nilvebrant, Nils-Olof
    STFI-Packforsk, Stockholm, Sweden.
    Jönsson, Leif J.
    Karlstad University, Faculty of Technology and Science.
    Optimal conditions for alkaline detoxification of dilute-acid lignocellulose hydrolysates.2006In: Applied Biochemistry and Biotechnology, ISSN 0273-2289, E-ISSN 1559-0291, Vol. 129-132, p. 599-611Article in journal (Refereed)
    Abstract [en]

    Alkaline detoxification strongly improves the fermentability of dilute-acid hydrolysates in the production of bioethanol from lignocellulose with Saccharomyces cerevisiae. New experiments were performed with NH4OH and NaOH to define optimal conditions for detoxification and make a comparison with Ca(OH)2 treatment feasible. As too harsh conditions lead to sugar degradation, the detoxification treatments were evaluated through the balanced ethanol yield, which takes both the ethanol production and the loss of fermentable sugars into account. The optimization treatments were performed as factorial experiments with 3-h duration and varying pH and temperature. Optimal conditions were found roughly in an area around pH 9.0/60 degrees C for NH4OH treatment and in a narrow area stretching from pH 9.0/80 degrees C to pH 12.0/30 degrees C for NaOH treatment. By optimizing treatment with NH4OH, NaOH, and Ca(OH)2, it was possible to find conditions that resulted in a fermentability that was equal or better than that of a reference fermentation of a synthetic sugar solution without inhibitors, regardless of the type of alkali used. The considerable difference in the amount of precipitate generated after treatment with different types of alkali appears critical for industrial implementation.

  • 7.
    Alriksson, Björn
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Sárvári Horváth, Ilona
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Jönsson, Leif J.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Overexpression of Saccharomyces cerevisiae transcription factor and multidrug resistance genes conveys enhanced resistance to lignocellulose-derived fermentation inhibitors.2010In: Process Biochemistry, ISSN 1359-5113, E-ISSN 1873-3298, Vol. 45, no 2, p. 264-271Article in journal (Refereed)
  • 8. Martin, C.
    et al.
    Alriksson, Björn
    Sjöde, A.
    Nilvebrant, N.-O.
    Jönsson,, L. J.
    Dilute-sulphuric acid prehydrolysis of agricultural and agro-industrial residues for ethanol production2007In: Appl. Biochem. Biotechnol. 136-140, 339-352Article in journal (Refereed)
  • 9. Sjöde, A.
    et al.
    Alriksson, Björn
    Jönsson, L. J.
    Nilvebrant, N.-O
    The Potential in Bioethanol Production from Fiber Sludges in Pulp Milled-Based Biorefineries2007In: Appl. Biochem. Biotechnol. 136-140, 327-338Article in journal (Refereed)
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