USE OF HEMICELLULOSE HYDROLYSATE FOR BETA-GLUCOSIDASE FERMENTATION

Hydrolysis of cellulose by Trichoderma cellulases often results in a m ixture of glucose, cellobiose, and low-mol-wt cellodextrins. Cellobios e is nonfermentable for most yeasts, and therefore it has to be hydrol yzed to glucose by beta-glucosidase prior to ethanol fermentation. In the present study, the beta-glucosidase production of one Penicillium and three Aspergillus strains, which were previously selected out of 2 4 strains, was investigated on steam pretreated willow. Both steam-pre treated willow and hemicellulose hydrolysate, released during steam ex plosion of willow, were used as carbon sources. Reference cultivation runs were performed using prehydrolyzed Solka Flee and glucose. The fo ur strains were compared with Trichoderma reesei regarding sugar consu mption and beta-glucosidase production. Aspergillus niger and Aspergil lus phoenicis proved to be the best enzyme producers on hemicellulose hydrolysate. The maximum beta-glucosidase activity, 4.60 IU/mL, was ob tained when A. phoenicis was cultivated on the mixture of hemicellulos e hydrolysate and steam-pretreated willow. The maximum yield of enzyme activity, 502 IU/g total carbohydrate, was obtained when Aspergillus foetidus was cultivated on the hemicellulose hydrolysate.