Design of highly efficient cellulase mixtures for enzymatic hydrolysis of cellulose.

An extremely highly active cellobiohydrolase (CBH IIb or Cel6B) was isolated from Chrysosporium lucknowense UV18-25 culture filtrate. The CBH IIb demonstrated the highest ability for a deep degradation of crystalline cellulose amongst a few cellobiohydrolases tested, including C. lucknowense CBH Ia, Ib, IIa, and Trichoderma reesei CBH I and II. Using purified C. lucknowense enzymes (CBH Ia, Ib, and IIb; endoglucanases II and V; beta-glucosidase, xylanase II), artificial multienzyme mixtures were reconstituted, displaying an extremely high performance in a conversion of different cellulosic substrates (Avicel, cotton, pretreated Douglas fir wood) to glucose. These mixtures were much or notably more effective in hydrolysis of the cellulosic substrates than the crude multienzyme C. lucknowense preparation and other crude cellulase samples produced by T. reesei and Penicillium verruculosum. Highly active cellulases are a key factor in bioconversion of plant lignocellulosic biomass to ethanol as an alternative to fossil fuels.

Evaluation of cellulase preparations for hydrolysis of hardwood substrates.

Seven cellulase preparations from Penicillium and Trichoderma spp. were evaluated for their ability to hydrolyze the cellulose fraction of hardwoods (yellow poplar and red maple) pretreated by organosolv extraction, as well as model cellulosic substrates such as filter paper. There was no significant correlation among hydrolytic performance on pretreated hardwood, based on glucose release, and filter paper activity. However, performance on pretreated hardwood showed significant correlations to the levels of endogenous beta-glucosidase and xylanase activities in the cellulase preparation. Accordingly, differences in performance were reduced or eliminated following supplementation with a crude beta-glucosidase preparation containing both activities. These results complement a previous investigation using softwoods pretreated by either organosolv extraction or steam explosion. Cellulase preparations that performed best on hardwood also showed superior performance on the softwood substrates.

Enzymatic hydrolysis of steam-exploded and ethanol organosolv-pretreated Douglas-Firby novel and commercial fungal cellulases.

Softwood residues are the most abundant feedstock available for bioconversion in many northern countries. However, the high costs for delignification and enzymatic hydrolysis currently deter commercialization of softwood bioconversion processes. This study evaluates the abilities of two novel fungal preparations (MSUBC1 and MSUBC2) and two commercial cellulase preparations (TR1 and TR2) to hydrolyze cellulose in Douglas-firpretreated by steam explosion or ethanol organosolv process. MSUBC1 showed significantly better performance than the other preparations on both lignocellulosic substrates. In particular, MSUBC1 achieved >76% cellulose conversion for hydrolysis of steam-exploded Douglas-fir (approximately 44% lignin) after 72 h at low enzyme loading (10 filter paper units/g of cellulose) and without beta-glucosidase supplementation.