Cellulolytic Activity of Wild-Type Fungi on Rice Bran (Oryza glaberrima Linn) using Submerged and Solid State Fermentation

Abstract

Cellulases are a group of hydrolytic enzymes capable of hydrolyzing the most abundant organic polymer on earth, cellulose, to smaller sugar components including glucose subunits. Therefore they have enormous industrial potential. This study was aimed at screening for the cellulolytic ability of fungi from an agro-based waste; rice bran (RB) (Oryza glaberrima). Cellulolytic fungi were isolated from RB and screened for cellulase activity on Mandel's Mineral medium supplemented with 1% Carboxyl methylcellulose (CMC). Aspergillus niger (ATCC 16404) served as the control organism. Total cellulase activity assay (FPase) was carried out to screen for the most efficient cellulase producers among the isolated fungi using submerged (SmF) and Solid-state (SSF) fermentations at 28± 2⁰C for 120 h using CMC as control substrate. Ten fungal isolates were obtained, out of which eight were found to possess cellulose degrading ability as indicated by the diameter of clear, hydrolyzed zones on the medium. These cellulolytic fungi belonged to five genera: Aspergillus, Fusarium, Penicillium, Saccharomyces and Rhizopus. Among the isolates, strains of  Penicillium citrinum, Penicillium chrysogenum, Aspergillus niger, Saccharomyces cerevisiae, Fusarium oxysporium, Aspergillus flavus and A.niger.were considered as potent producers of cellulase. Cellulase activity was generally higher with SSF than SmF. Crude enzyme filtrates of P. citrinum, produced the highest cellulase activity of 0.070 FPUml^-1 and 0.080 FPUml^-1, while F. oxysporium had the lowest cellulase activity of 0.047 FPUml^-1 and 0.051 FPUml^-1 in SmF and SSF respectively. Penicillium. citrinum was found to be a good prospect in cellulase production, in which case rice bran a suitable inexpensive substrate for its production.