Screening Wild and Mutant Strains of Aspergillus flavus and Aspergillus niger Isolated from Plantain Stalks for Amylase Production

摘要

This study is conducted to determine the amylase activity of wild and mutant strains of Aspergillus flavus and Aspergillus niger isolated from plantain stalks. The isolation of the fungal species was carried out using standard microbiological methods. Strain improvement of the fungal isolates was carried out by exposing the wild fungal species to ultraviolet (UV) radiation at 240nm for ten, twenty, and thirty minutes. The amylase production from the wild and mutant strains was examined quantitatively while the effects of pH and temperature on the amylase activities of the wild and mutant strains were determined. Three mutant strains were obtained from each of Aspergillus flavus and Aspergillus niger. The wild and mutant strains of the fungal isolates showed variations in the amylase production. The amount of amylase produced by the fungal strains ranged from 2.849 mg/mL/min to 3.263 mg/mL/min of which the mutant strains of Aspergillus niger, exposed for ten minutes showed the highest amylase production. Furthermore, the amylase activities of the wild and mutant strains of the fungal species were sensitive to changes in pH and temperature. Amylase was optimally produced from all the fungal strains at pH 6 and 25oC. This study has revealed the amylase producing potential of wild and mutant (irradiated) strains of Aspergillus flavus and Aspergillus niger. Therefore, the mutated strains of Aspergillus flavus and Aspergillus niger could be employed in the commercial production of amylase. Findings from this study are promising; however, further intensive studies are still needed on the improved strains as well as the purification and characterization of the enzyme.