Properties of Aspergillus flavus Cellulase Produced from Solid State Fermentation of Brewers’ Spent Grain (BSG) as Substrate

Abstract

The production of cellulase from Aspergillus flavus isolated from Brewers’ Spent Grain (BSG) undergoing bio-deterioration was carried out using solid state fermentation method. Out of a total of four fungal isolates with cellulase producing potentials, Aspergillus flavus with a clearance zone of 5.0cm was the best hyper-producer and was selected for optimization and cellulase production. Two different enzyme production media containing either yeast extract or potassium nitrate (KNO3) served as sources of nitrogen to the Aspergillus flavus. The crude activity of the potassium nitrate (KNO3) option (28,170 Units) was significantly higher than the crude cellulase from yeast extract option (18,600 Units). Ammonium sulphate precipitation at 60%, 80%, and 100% had cellulase activities 14600 units, 4400 unit, and 2800uits in yeast extract amended experimental option. In addition, ammonium sulphate precipitation at 60%, 80%, and 100% gave cellulase activities of 21130 units, 1700 units, and 1110 units, respectively in the KNO3 amended experimental option. Thus, 60% ammonium sulphate precipitation gave the best cellulase activity. The optimum pH of Aspergillus flavus cellulase was 6.0, while the optimum temperatures were between 50°C to 60°C. Tolerance to some alkali and alkaline–earth metals was also established, and probable co-factor behaviour of manganese ion to this cellulase was also established. Good government policies that support high import duties on foreign enzymes, emphasis on local production are advocated for in order to stamp out the economic leakages accruing through enzyme importation into Nigeria.