Submitted to: Applied Biochemistry and Biotechnology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/4/2005
Publication Date: 4/1/2005
Citation: Li, X., Dien, B.S., Cotta, M.A., Wu, Y., Saha, B.C. 2005. Profile of enzyme production of Trichoderma reesei grown on corn fiber fractions. Applied Biochemistry and Biotechnology. 121-124:321-334. Interpretive Summary: Efficient conversion of lignocellulosic biomass such as corn fiber, rice straw, and corn stalk to fermentable sugars has been recognized as the major bottleneck for the economical production of biofuels and feedstock chemicals from the almost infinite renewable resources. There are three major constitutes, cellulose, hemicellulose, and lignin, commonly found in lignocellulosic biomass. Biological degradation of the three constitutes requires many different enzymes to work together as a consortium, but the most needed enzymes are those which tackle cellulose and hemicelluloses. For complete hydrolysis of cellulose and hemicellulose, enzymes required are cellobiohydrolases, endoglucanases, beta-glucosidases, xylanases, beta-xylosidases, alpha-arabinofuranosidases, phenolic and acetyl xylan esterases, alpha-glucuronidases, and alpha-galactosidases. The fungus is the most commonly used organism for large-scale production of commercial cellulases and hemicellulases and holds the best hope to be developed for cost-effective production of enzymes for lignocellulosic biomass conversion. Grown on pure cellulose or lactose, the fungus produces mostly cellulases but the efficient degradation of lignocellulose required a balanced spectrum of both types of enzymes. This study investigated the potential of corn fiber, a readily available and inexpensive waste biomass, for production of a balanced suite of both cellulases and hemicellulases. The work also demonstrated that the enzymes produced by the fungus grown on corn fiber and its cell wall components can hydrolyze pretreated biomass more efficiently than those produced by the fungus grown on purer substrates.
Technical Abstract: Corn fiber is the fibrous by-product of wet-mill corn processing. It typically consists of about 20% starch, 14% cellulose, and 30% hemicellulose in the form of arabinoxylan. Crude corn fiber (CCF) was fractionated into de-starched corn fiber (DSCF), corn fiber with cellulose (CFC) enriched, and corn fiber arabinoxylan (CFAX), and these fractions were evaluated as substrates for enzyme production by Trichoderma reesei. T. reesei QM9414 and Rut C-30 grew on CCF, DSCF, CFC, or CFAX and secreted a number of hydrolytic enzymes. The enzymes displayed synergism with commercial cellulases for corn fiber hydrolysis.