PRODUCTION OF CELLULASE BY SOLID STATE FERMENTATION OF BREWERY SPENT GRAINS USING ASPERGILLUS NIGER FGSC A733

Abstract

Brewery spent grains (BSG) is a waste product of the brewing process. BSG has been used as animal feed, production of value added products, substrate for growth of microorganisms and for extraction of proteins and acids. BSG is high in lignocellulosic matter and may be a candidate substrate for the production of lignocellulolytic enzymes (cellulases and xylanases). In this study, BSG was evaluated for use as a cheap and readily available substrate for the production of extracellular cellulase by Aspergillus niger FGSC A733 during solid state fermentation. The brewery spent grains were subjected to fermentation by Aspergillus niger FGSC A733 at different temperatures ranging from 30 - 40 °C and initial pH ranging from 4.0 - 6.0 for process optimization. Time course analysis was done to determine the optimum incubation period for maximum cellulase production. The effect of alkaline pre-treatment of the substrate on the production of cellulase was analyzed. Cellulase activity was determined by estimating the amount of reducing sugars produced by the enzymes using 3.5 dinitrosalycyclic acid (DNS). Maximum cellulase production was at 35 °C, pH 5.0 and an optimum incubation period of 72 hours. Under optimized conditions, a yield of 73.33 U of cellulase/gram of substrate was obtained. Pre-treatment of the spent
grains resulted in a three-fold increase in the production of cellulase. BSG was found to be a suitable substrate for production of cellulase.