Ethanol Production by High-Solids Simultaneous Saccharification and Fermentation of Cellulose-Enriched Barley Straw and Hull Residues Obtained by Alkaline Hydrogen Peroxide Pretreatment

Abstract

Abstract Barley straw and hull were both subjected to alkaline hydrogen peroxide treatment for extraction of the hemicellulose fractions. the cellulose-enriched residues were then used as substrates for ethanol production in a high-solids fed-batch simultaneous saccharification and fermentation (SSF) process using commercial Sacharomyces cerevisiae and YRH400, a S. cerevisiae strain genetically engineered for xylose metabolism. The total process time was 8 days, with the first day dedicated solely to enzymatic hydrolysis and the remaining time for the SSF. Higher ethanol production was obtained with YRH400 with both residues. The final ethanol concentrations produced from the cellulose-enriched residue of barley straw by the commercial yeast and YRH400 were 63.8 g/L and 73.1 g/L, respectively, while the corresponding ethanol yields were 0.10 g/g and 0.12 g/g. The tendency of the cellulose-enriched residue of barley hull to absorb more water caused the formation of a highly viscous slurry that prevented go...