Production and Characterization of Extracellular Protease Enzyme from Aspergillus Niger Using Different Agro-Industrial Residues

Protease enzymes have many applications and are used in many industries including textile, detergent and pharmaceuticals. This work was aimed to produced extracellular protease enzyme from Aspergillus niger using different agro-industrial wastes, determine the effect of incubation periods, substrate concentration, pH and temperature on the enzyme activity. Aspergillus niger was isolated from local soil and used to produced extracellular protease enzyme under solid state fermentation conditions using wheat bran, rice husk, maize chaff and potato peel. Wheat bran proved to be the best substrate for protease production with highest yield of enzyme (0.94µg/ml) while potato peel had the least yield (0.46µg/ml). Fermentation carried at 96 hours produced the highest enzyme yield (0.95µg/ml) while least enzyme production (0.32µg/ml) was obtained at 144 hours. High concentration of casein (16 mg/ml) as substrate resulted in highest protease activity of 0.44µg/ml. The optimum pH for protease activity was 9 with maximum activity of 0.66µg/ml while the optimum temperature for protease activity was 45 0 C with maximum activity of 0.86µg/ml. The highest protease activity obtained at high pH and temperature showed that the enzyme produced by the Aspergillus niger is an alkaline protease and thermostable.