Increase of the a-amylase yield by Some Bacillus Strains

Abstract

In order to obtain high amounts of a-amylase enzyme from Bacillus bacteria a new medium was developed. In this medium, three strains of Bacillus bacteria were grown in the presence of different carbon, nitrogen and metal ions. The highest a-amylase yield was obtained by addition of Na-citrate, strach and sucrose for the strains of B. subtilis, B. amyloliquefaciens I and B. amyloliquefaciens II, respectively. As a nitrogen source, yeast extract was found to be effective on enzyme yield for B. subtilis and B. amyloliquefaciens II, while ammonium sulfate was found to be effective for B. amyloliquefaciens I. None of the metal ions increased the enzyme activity of all the strains. However, a slight increase was determined by increase of oxygen concentration. The optimum temperature of each bacteria for a-amylase was 55°C. The optimum pH of the B. subtilis enzyme was 7.0, while for both strains of B. amyloliquefaciens the optimum pH was 5.9. Enzymes were not stable at elevated temperatures and at low or high pH values. Inhibitory effects of Ag, Zn and Cu were observed in all Bacillus strains. Maltose and a small amount of glucose were determined as the split products of starch by thin layer chromatography (TLC) after incubation of starch with amylases of all the strains used in this study.