Production of cellulose and hemicellulose-degrading enzymes by filamentous fungi cultivated on wet-oxidised wheat straw

The production of cellulose and hemicellulose-degrading enzymes by cultivation of Aspergillus niger ATCC 9029, Botrytis cinerea ATCC 28466, Penicillium brasilianum IBT 20888, Schizophyllum commune ATCC 38548, and Trichoderma reesei Rut-C30 was studied. Wet-oxidised wheat straw suspension supplemented with NH4NO3, MgSO4, and KH2PO4 was used as cultivation medium aiming to obtain an enzyme mixture optimal for enzymatic hydrolysis of wet-oxidised wheat straw. The cultivations with B. cinerea and R brasilianum gave the highest endoglucanase (EC 3.2.1.4) and beta-glucosidase (EC 3.2.1.21) activities, in contrast to the other fungi where lower activities were found. The culture filtrates were concentrated by ammonium sulphate precipitation. After enzyme concentration, the highest enzyme activities (1.34 FPU/ml) were found in the culture broth originating from P. brasilianum. Enzymatic hydrolysis of filter cake from wet-oxidised wheat straw for 48 h with an enzyme loading of 5 FPU/g biomass resulted in glucose yields from cellulose of 58% (w/w) and 39% (w/w) using enzymes produced by R brasilianum and a commercial enzyme mixture, respectively. At higher enzyme loading (25 FPU/g biomass) using either enzyme mixtures the glucose yield from cellulose was in the range of 77-79% (w/w).