Enzymatic hydrolysis and simultaneous saccharification and fermentation of steam-pretreated spruce using crude Trichoderma reesei and Trichoderma atroviride enzymes

The aim of this study was to compare the performance of the enzymes produced by Trichoderma reesei Rut C30 and the good extracellular beta-glucosidase-producing mutant Trichoderma atroviride TUB F-1663 to that of commercial preparations in the enzymatic hydrolysis and the simultaneous saccharification and fermentation (SSF) of steam-pretreated spruce (SPS). The concentrated TUB F-1663 enzyme was found to be the most efficient in the hydrolysis of washed SPS at 50 g/L water-insoluble solids (WIS) in terms of the glucose produced (18.5 g/L), even in comparison with commercial cellulases (14.1-16.7 g/L). The enzyme preparations were studied at low enzyme loadings (5 FPU/g WIS) in SSF to produce ethanol from SPS. The enzyme supernatant and whole fermentation broth of T. atroviride as well as the whole broth of T. reesei proved to be as efficient in SSF as the commercial cellulase mixtures (ethanol yields of 61-76% of the theoretical were achieved), while low ethanol yields (<40%) were obtained with the beta-glucosidase-deficient T. reesei supernatant. Therefore, it seems, that instead of using commercial cellulases, the TUB F-1663 enzymes and the whole broth of Rut C30 may be produced on-site, using a process stream as carbon source, and employed directly in the biomass-to-bioethanol process. (C) 2009 Elsevier Ltd. All rights reserved.