Successive cultivation of selected cellulolytic fungi on rice straw and wheat bran for economic production of cellulases and D-xylanase.

Production of cellulase [1,4-(1,3;1,4)-fl-o-glucan 4-glucanohydrolase, EC 3.2.1.4], fl-D-glucosidase (fl-Dglucoside
glucanohydrolase, EC 3.2.1.21) and o-xylanase (1,4-fl-D-xylan xylanohydrolase, EC 3.2.1.8) by
successive cultivation of Aspergillus ustus, Trichoderma sp. (a), Trichoderma sp. (b), Botrytis sp. and Sporotrichum
pulverulentum on rice straw (RS) and wheat bran (WB) substrates by solid state fermentation and
concurrent degradation of the substrates were studied. For every gram of dry RS used, it was possible to
obtain 14 U filter paper activity (FPA), 22 U carboxymethylcellulase (CMCase), 48 U fl-o-glucosidase and
1431 U D-xylanse, after recycling the same substrate five times. This also resulted in 55% loss, by weight of
the substrate, 64% in fibre, 32% in lignin and 46% in minerals. WB under similar conditions of successive
cultivation could yield 8 U FPA, 19 U CMCase, 81 U fl-D-glucosidase and 788 U D-xylanase. Concurrently,
the total loss in substrate was 73%, the decrease in fibre was 52%, lignin 28% and minerals 86%. Amount of
crude protein in the residual RS and WB was 7.2 and 10.3% respectively. The data indicate that a single
fungal isolate could be grown on a substrate for five successive cycles but that the enzyme yields were less
than when different strains were employed.