Production of Mannan-degrading enzyme by Aspergillus niger

Three local fungal isolates (Aspergillus flavus, A. niger and A.ochraceous) were screened for their ability to secrete digesting enzymes (endoglucanase; β-galactosidase; β-mannanase; β-mannosidase and xylanase). The results revealed that the highest activity detected in the culture filtrate was for the β-mannanase enzyme followed by xylanase, whereas endoglucanase and β-galactosidase activities were very low. On the other hand, the culture filtrate did not contain any activity for β-mannosidase. The most potent mannanase producer was A. niger, which produced the highest extracellular mannanase activity (2.90U/ml), followed by Aspergillus flavus (2.54 U/ml) and A. ochraceous (2.16 U/ml). The optimal operating conditions for β-mannanase activity by A. niger arising from this study are as follows: temperature of 30°C, 6 days incubation period, initial pH 5.0 and inoculum size of 3 × 106 spore/ml.