Preliminary screening for endoglucanase, cellobiohydrolase and beta-glucosidase

Cellulases are a group of indispensable enzymes whose market value is projected to increase to billions of dollars in the next few years. This study aimed at screening for the endoglucanase-, cellobiohydrolase-, and beta-glucosidase-producing fungi from rice husks in husk piles. Isolation of the mycoflora of rice husks was done using Potato dextrose agar and carboxy methyl cellulase media. The qualitative screening was done by measuring the zone of hydrolysis after flooding pure colonies plated singly in petri dishes, with Congo red solution. The quantitative screening was done at the end of 120 hours submerged fermentation, by assaying for enzyme production after the growth of colony in mineral media specific for the production of each class of cellulase: endoglucanase, cellobiohydrolase and beta-glucosidase. The genera of fungi isolated were Absidia, Alternaria, Aspergillus, Cladosporium, Fusarium, Geotrichum and Penicillium species. The most abundant fungi isolated was Aspergillus flavus (18.18%) while the least abundant isolates were Aspergillus restrictus, Alternaria sp. and Geotrichum sp., with percentage frequencies of 3.03% each. Eleven of the isolates were found to produce cellulase by zones around colonies, indicating cellulose hydrolysis. The most prolific endoglucanase producer was Fusarium incarnatum with 16.60 U/ml at the 120th hour, while the best cellobiohydrolase and beta-glucosidase producer was Penicillium expansum, producing 3.10 U/ml of cellobiohydrolase and 44.41 U/ml of beta-glucosidase at its 120th hour of incubation. These isolates show promising potentials for optimization studies and for eventual employment in biotechnological and enzyme-utilizing industries.