Critical conditions for improved fermentability during overliming of acid hydrolysates from spruce.
ABSTRACT Bioethanol can be produced from wood via acid hydrolysis, but detoxification is needed to achieve good fermentability. Overliming was investigated in a factorial designed experiment, in which pH and temperature were varied. Degradation of inhibitory furan aldehydes was more extensive compared to monosaccharides. Too harsh conditions led to massive degradation of sugars and formation of inhibiting acids and phenols. The ethanol productivity and yield after optimal overliming reached levels exceeding reference fermentations of pure glucose. A novel metric, the balanced ethanol yield, which takes both ethanol production and losses of fermentable sugars into account, was introduced and showed the optimal conditions within the investigated range. The findings allow process technical and economical considerations to govern the choice of conditions for overliming.
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ABSTRACT: Ethanol produced from various lignocellulosic materials such as wood, agricultural and forest residues has the potential to be a valuable substitute for, or complement to, gasoline. This paper reviews the research activities in Sweden on development of the technology for ethanol production from lignocellulosics. The paper focuses on hemicellulose and cellulose hydrolysis and fermentation as well as on process integration and techno-economic evaluation of the overall process.
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ABSTRACT: Bioconversion of lignocellulose by microbial fermentation is typically preceded by an acidic thermochemical pretreatment step designed to facilitate enzymatic hydrolysis of cellulose. Substances formed during the pretreatment of the lignocellulosic feedstock inhibit enzymatic hydrolysis as well as microbial fermentation steps. This review focuses on inhibitors from lignocellulosic feedstocks and how conditioning of slurries and hydrolysates can be used to alleviate inhibition problems. Novel developments in the area include chemical in-situ detoxification by using reducing agents, and methods that improve the performance of both enzymatic and microbial biocatalysts.Biotechnology for Biofuels 01/2013; 6(1):16. · 5.55 Impact Factor
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ABSTRACT: Two treatments, an induced autohydrolysis and an acid hydrolysis, were applied to Eucalyptus globulus wood chips prior to the cooking stage to extract the hemicellulosic fraction that otherwise would be dissolved in the black liquor and burnt in the recovery boiler. The obtained hydrolysates, rich in xylose, were detoxified by overliming and used for ethanolic fermentation. Impacts of each wood pretreatment on the kraft cooking process and on the quality of the produced pulp were evaluated. Both pretreatments promoted an increase in the cooking rate, but had a negative effect on pulp quality and overall yield. Autohydrolysis showed a less negative influence. However, autohydrolysates led to lower values of ethanol concentration, productivity and yield compared to the fermentation of acid hydrolysates. To get more profit from the autohydrolysates they were also submitted to secondary acid hydrolysis and vacuum evaporation processes. Overliming followed by evaporation (with a concentration factor of 3) gave better results than the inverse method. This procedure raised the fermentable sugar content and led to the production of ethanol with a concentration of ~10 geth L-1 (productivity of 0.23 geth L-1 h-1 and yield of 0.50 geth gxyl eq -1) which compares well with the results obtained with the fermentation of acid hydrolysates.XXI TECNICELPA Conference and Exhibition - VI Iberoamerican Congress on Pulp and Paper Research - CIADICYP 2010; 10/2010