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- Alriksson, Björn, et al.
(author)
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Optimal conditions for alkaline detoxification of dilute-acid lignocellulose hydrolysates.
- 2006
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In: Applied Biochemistry and Biotechnology. - 0273-2289 .- 1559-0291. ; 129-132, s. 599-611
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Journal article (peer-reviewed)abstract
- 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.
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| 3. |
- Cassland, Pierre, et al.
(author)
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Evaluation of Oxalate Decarboxylase and Oxalate Oxidase for Industrial Applications
- 2010
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In: Applied biochemistry and biotechnology. - : Humana Press. - 1559-0291 .- 0273-2289. ; 161:1-8, s. 255-63
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Journal article (peer-reviewed)abstract
- Increased recirculation of process water has given rise to problems with formation of calcium oxalate incrusts (scaling) in the pulp and paper industry and in forest biorefineries. The potential in using oxalate decarboxylase from Aspergillus niger for oxalic acid removal in industrial bleaching plant filtrates containing oxalic acid was examined and compared with barley oxalate oxidase. Ten different filtrates from chemical pulping were selected for the evaluation. Oxalate decarboxylase degraded oxalic acid faster than oxalate oxidase in eight of the filtrates, while oxalate oxidase performed better in one filtrate. One of the filtrates inhibited both enzymes. The potential inhibitory effect of selected compounds on the enzymatic activity was tested. Oxalate decarboxylase was more sensitive than oxalate oxidase to hydrogen peroxide. Oxalate decarboxylase was not as sensitive to chlorate and chlorite as oxalate oxidase. Up to 4 mM chlorate ions, the highest concentration tested, had no inhibitory effect on oxalate decarboxylase. Analysis of the filtrates suggests that high concentrations of chlorate present in some of the filtrates were responsible for the higher sensitivity of oxalate oxidase in these filtrates. Oxalate decarboxylase was thus a better choice than oxalate oxidase for treatment of filtrates from chlorine dioxide bleaching.
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| 7. |
- Sjöde, Anders, 1977-
(author)
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Chemical characterization in the biorefinery of lignocellulose : Formation and management of oxalic acid and analysis of feedstocks for bioethanol production
- 2008
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Doctoral thesis (other academic/artistic)abstract
- The pulp and paper industry is entering a new era. Pulp mills will be transformed to biorefineries that produce not only pulp, but also biofuels and novel products from lignocellulose. This thesis addresses problems connected with the industrial transition to environmental-friendly technologies and the implementation of the biorefinery concept. Peroxide bleaching and enhanced recirculation of process water may lead to increased problems with oxalate scaling. Enzymatic elimination of the oxalate problem could be the ultimate industrial solution. The activities of oxalate oxidase, oxalate decarboxylase and a novel oxalate-degrading enzyme provided by Novozymes have been tested in industrial bleaching filtrates. Chemical characterization of the filtrates was used in combination with multivariate data analysis to identify potential enzyme inhibitors. A method based on oxalate oxidase was developed to determine the levels of oxalic acid in process water. The precursors of oxalic acid formed during bleaching of pulp have been reassessed. New experimental data indicate that alkaline oxidative degradation of dissolved carbohydrates is the main source of oxalic acid. These findings are contradictory to previous hypotheses, which have been focused on lignin. Xylan was more important than lignin as precursor of oxalic acid under peroxide-bleaching conditions. Hot-water extraction of hemicelluloses from softwood mechanical pulp prior to the peroxide-bleaching stage reduced the formation of oxalic acid by one third. Lignocellulosic materials were characterized chemically with regard to their suitability as feedstocks in biorefineries producing bioethanol. Four agricultural and agro-industrial residues were investigated; cassava stalks, peanut shells, rice hulls, and sugarcane bagasse. Pretreated sugarcane bagasse was the material that was most susceptible to hydrolysis by cellulolytic enzymes. Waste fiber sludges from three pulp mills were characterized. The waste fiber sludge with the lowest content of lignin was hydrolyzed most efficiently by the enzymes. Oligomeric xylan fragments were isolated as by-products from a waste fiber sludge. Hydrolysis of the waste fiber sludges resulted in solid residues with improved fuel properties. The waste fibers were found to be suitable as a feedstock for the production of biofuels in a pulp mill-based biorefinery.
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| 10. |
- Winestrand, Sandra, et al.
(author)
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Evaluation of Oxalate Decarboxylases in Industrial Bleaching Filtrates and in Pulp-Mill Experiments
- 2014
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In: Industrial Biotechnology. - : Mary Ann Liebert. - 1550-9087 .- 1931-8421. ; 10:2, s. 126-129
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Journal article (peer-reviewed)abstract
- Precipitation of sparsely soluble calcium oxalate causes scaling problems in the pulp and paper industry. A potential solution is to degrade the oxalic acid using oxalate-degrading enzymes. Four novel fungal oxalate decarboxylases were evaluated in experiments with 16 pH-adjusted bleaching filtrates collected from mills producing mechanical pulp or kraft pulp. The enzymes were also tested in five of the filtrates from mechanical pulping at authentic pH and elevated temperature (55°C). The enzyme that performed best in the screening was selected for a small-scale experiment performed in a mill producing mechanical pulp. The enzyme degraded 70% of the oxalic acid in the fresh filtrate after one hour, without pH adjustment and at the prevailing process temperature (65°C). The new enzyme performed considerably better than the well-studied oxalate decarboxylase from Aspergillus niger, which only degraded 4% of the oxalic acid under the same conditions.
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