Improvement of yields and rates during enzymatic hydrolysis of cellulose to glucose. Final report, December 1, 1978-January 31, 1980

The production of sugars by enzymatic hydrolysis of cellulose is a multistep process which includes conversion of the intermediate cellobiose to glucose by ..beta..-glucosidase. Aside from its role as an intermediate, cellobiose inhibits the endogluconase components of typical cellulase enzyme systems. Because these enzyme systems often contain insufficient concentrations of ..beta..-glucosidase to prevent accumulation of inhibitory cellobiose, this research investigated the use of supplemental immobilized ..beta..-glucosidase to increase yields of glucose. Immobilized ..beta..-glucosidase from Aspergillus phoenicis was produced by sorption on controlled-pore alumina with about 90% activity retention. The product lost only about 10% of the original activity during an on-stream reaction period of 500 hours with cellobiose as substrate; maximum activity occurred near pH 3.5 and the apparent activation energy was about 11 k cal/mole. The immobilized ..beta..-glucosidase was used together with Trichoderma reesei cellulase to hydrolyze cellulosic materials, such as Solka Floc, corn stover and exploded wood. Increased yields of glucose and greater conversions of cellobiose to glucose were observed when the reaction systems contained supplemental immobilized ..beta..-glucosidase.