Partial purification, characterization and hydrolytic activities of amylases from Bacillus licheniformis and Aspergillus niger cultured on agricultural residues

Abstract

α-Amylase and amyloglucosidase produced by amylolytic Bacillus licheniformis and Aspergillus niger isolated from plantain and yam peels media were partially purified and characterized. Following cultivation of the microbial isolates on the agricultural residue media, crude enzyme solutions were obtained by filtration and centrifugation techniques. Crude α-amylase and amyloglucosidase produced were partially purified with salting-out process, involving ammonium sulphate, after which their pH and thermal characteristics were determined using standard biochemical methods. Partially purified amylases were subsequently employed in hydrolysis of each of starch samples of cassava, maize, sorghum and millet prepared in the laboratory. The results show the specific activity, pH and thermal stabilities of the α-amylase to be 32.75 U, 5.6 to 7.0 and 20 to 60°C, respectively. Partially-purified amyloglucosidase exhibited a specific activity of 2.93 U, pH (4.2 to 5.6) and thermal stabilities (20 to 50°C). Hydrolysates of the four starch samples were also found to be mainly maltose and glucose as revealed on the TLC plates.

Key words: α-Amylase, amyloglucosidase, partial-purification, hydrolysate, starch.