Effects of Some Variable Factors on Cellulase Production by Aspergillus Niger using Solid State Fermentation

Abstract

Several agro-wastes end up in landfills in Nigeria. there has been a renewed interest in the recycling of such agricultural waste for value-addition through innovative methods. This process will reduce environmental pollution and generates additional useful products.  Corn cob is one of the largest farm-originating underutilized waste nuisances in Nigeria. Despite their high metabolizable sugars, not all microbial strains utilize them in the same way and rates. Cellulase is an industrially important products, essential for human activities. This study aimed to use corn cobs as substrates of cellulase enzyme production, determine the effects of the Aspergillus niger strains, (cellulosic or non-cellulosic) as well as the time of fermentation on the enzyme yields.  Cellulosic and non-cellulosic niches were screened for Aspergillus strains. Aliquot 0.1ml of the serially diluted samples were pour-plated on Streptomycin-containing potato dextrose Agar (PDA). The Aspergillus niger obtained were identified by microscopic examination using lactophenol cotton blue staining and then screened in a cellulose-containing medium for their cellulase activity. Strains with the highest zones of clearance were selected for further studies. The enzyme activity of Aspergillus niger strains was from day 2 to the 10^th day of fermentation. The highest performance across the strains was on the 6^th day by Aspergillus niger RA23, 1.032 U/ml) and the lowest was 0.372 U/ml by Aspergillus niger RA05. Enzyme production was influenced by fermentation time and microbial strain agreeing with previous literatures that fermentation process is strain-dependent. The microbial strain used for bioprocessing has important function in the metabolism and transport of nutrients. Therefore, autochthonous factor needs to be considered in strain selections.