Kinetic properties of α-amylase produced by Bacillus megaterium RAS103 under optimum conditions in submerged fermentation

Abstract

THE CURRENT investigation is aimed to optimize the culture conditions for α-amylase production by Bacillus megaterium isolated from rabbit manure as well as to study the kinetic properties of the produced amylase. Out of 38 bacterial isolates recovered from 10 rabbit manure samples, 7 isolates were selected as highly amylase producers onto starch agar medium. Interestingly, the bacterial isolate RAS103 was selected as the most highly producer for amylase with activity 81.76±0.12U/ml in starch mineral broth medium using submerged fermentation method. This isolate was identified based on the phenotypic and genotypic characteristics as Bacillus megaterium and deposited in the GenBank database with the accession number MH817142.1. Amylase activity was maximized to 106.39±2.36U/ml under the optimized culture conditions of a fermentation medium of 2% starch supplemented by 3g/L yeast extract, adjusted at pH 8.0, inoculated with 1% bacterial inoculum and incubated at 35°C for 24h. The Vmax (maximum reaction velocity) and Km (Michaelis constant) values of the produced amylase were 81.30U/ml and 0.878mg/ml, respectively, for hydrolysis of starch in a reaction mixture of pH 6.0 at 45°C for 20min. These findings suggest the applicability of using the bacterial isolate B. megaterium RAS103 as a potential producer of α-amylase for industrial purposes. Keywords: