Ethanol — Butanediol Fermentation of Xylose
Hemicellulose accounts for 10 to 40 percent of various forest and agricultural residues. Recent biomass conversion studies have stressed the need fo utilizing hemicellulose in fermentation process economics. The objective of this task has been to develop a fermentation process whereby the hemicellulose hydrolyzate obtained by mild acid hydrolysis of biomass are converted to fuel substances. Since hemicellulose is primarily a polymer of xylose, the emphasis was placed on successful conversion of xylose to ethanol and butanediol. Our batch level fermentation studies indicate that up to 11 percent xylose can be fully utilized yielding 45 percent w/w combined yield of ethanol and butanediol. Acetic acid and acetoin are the byproducts of fermentation. In order to utilize the hemicellulose hydrolyzate for ferementation, the inhibitory effect of the major byproducts of acid hydrolysis and products of fermentation were studied. It was found that furfural and acetic acid had the highest inhibition. The process was also optimized with respect to pH and degree of aeration. Mathematical modelling of the fermentation process indicated that project formation is mainly non-growth associated.
KeywordsBatch Fermentation Agricultural Residue Hemicellulose Hydrolyzate Xylose Consumption Ammonium Phosphate
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