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Bioconversion of wheat straw to ethanol: Chemical modification, enzymatic hydrolysis, and fermentation

Detroy, R.W., Lindenfelser, L.A., Sommer, S., Orton, W.L.
Biotechnology and bioengineering 1981 v.23 no.7 pp. 1527
wheat straw, alcoholic fermentation, ethanol production, ethanol, yeasts, Saccharomyces uvarum, pretreatment, chemical treatment, sulfuric acid, acid treatment, sodium hydroxide, alkali treatment, ammonium hydroxide, ethyleneimine, saccharification, enzymatic hydrolysis, cellulases, lignin, hemicellulose, cellulose
Native wheat straw (WS) was pretreated with various concentrations of H2SO4 and NaOH followed by secondary treatments with ethylene diamine (EDA) and NH4OH prior to enzymatic saccharification. Conversion of the cellulosic component to sugar varied with the chemical modification steps. Treatment solely with alkali yielded 51-75% conversions, depending on temperature. Acid treatment at elevated temperatures showed a substantial decrease in the hemicellulose component; EDA-treated WS (acid pretreated) showed a 69-75% decrease in the lignin component. Acid-pretreated EDA-treated straw yielded a 98% conversion rate, followed by 83% for alkali-NH4OH treated straws. In other experiments, WS was pretreated with varying concentrations of H2SO4 or NaOH followed by NH4OH treatment prior to enzymatic hydrolysis. Pretreatment of straw with 2% NaOH for 4 h coupled to enzymatic hydrolysis yielded a 76% conversion of the cellulosic component. Acid-base combination pretreatments yielded only 43% conversions. A reactor column was subsequently used to measure modification-saccharification-fermentation for wheat straw conversion on a larger scale. Thirty percent conversions of wheat straw cellulosics to sugar were observed with subsequent fermentation to alcohol. The crude cellulase preparation yielded considerable quantities of xylose in addition to the glucose. Saccharified materials were fermented directly with actively proliferating yeast cells without concentration of the sugars.