Submitted to: Irish Journal of Agricultural Research
Publication Type: Review Article
Publication Acceptance Date: January 15, 1996
Publication Date: N/A
Technical Abstract: The production of fuels and chemicals from cellulosic biomass has been extensively studied from an economic, biochemical and microbiological standpoint. While it is currently possible to produce ethanol from cellulosic substrates, economics dictate that the efficiency of production must be improved if fuel alcohol is to be competitive with either gasoline produced from crude oil or ethanol produced from starch. In current biomass processing schemes, after the cellulosic feedstock is pretreated, it is subjected to enzymatic saccharification with cellulase. One of the rate-limiting steps in the enzymatic hydrolysis of cellulose is the conversion of cellobiose to glucose by beta-glucosidase. C. wickerhamii produces a unique, extracytoplasmic beta-glucosidase that enables it to ferment cellobiose and cellodextrins. When C. wickerhamii was used in the simultaneous saccharification-fermentation of cellulose, 10% to 30% more ethanol was produced than in fermentations using S. cerevisiae. Biochemical and physiological studies have shown that this beta-glucosidase is not inhibited by glucose and that the enzyme is the rate-limiting step in the fermentation of cellobiose/cellodextrins by C. wickerhamii. The gene (bglB) encoding this enzyme was cloned and expressed in S. cerevisiae.