Production and Partial Purification of Beta-Mannanase from Aspergillus niger Associated with Ilaje Lake, Ondo State, Nigeria

Abstract

The present study aimed at the isolation, screening and partial purification of beta-mannanase from fungi isolated from soil and water samples collected from Ilaje Lake, Ondo state, Nigeria. The associated fungi were isolated and counted by standard microbiological methods. Partial purification of crude mannanase was done by standard biochemical methods. Quantitatively, mannanase production was performed in mineral salt medium into which Locust Bean Gum (LBG) had been incorporated as the sole carbon source. Enzyme activity was determined by dinitrosalicylic acid (DNSA) method, while protein content was evaluated by Lowry’s method. The highest fungal counts were recorded for water sample collected from Ilaje Lake with 3.4 × 108 SFU/mL. The organisms encountered include Aspergillus flavus, Rhizopus stolonifer, A. fumigatus, A. niger, R. japonicus, Penicillum italicum, Fusarium solani and Candida albicans. All the fungal isolates encountered from these sources showed varied degrees of mannanase activities. The highest specific mannanase activity was recorded for isolate 4B1, while the lowest value was obtained with isolate 1B2. Purification of crude mannanase from A. niger was carried out by ammonium sulphate precipitation and gel filtration (Sephadex G-200). Fractionation of ammonium sulphate precipitated mannanase from A. niger on Sephadex G-200 produced two activity peaks. In this investigation, fungal isolates evaluated for mannanase production from this source gave appreciable mannanase activity and this could be applied in many industrial processes.