Effect of starch containing organic substrates on alpha amylase production in Bacillus strains

Abstract

This study was conducted to identify and screen indigenous Bacillus strains from different soil samples for alpha amylase activity. Strains positive for the enzyme activity wereBacillus subtilis, Bacillus mycoids, Bacillus licheniformis and Bacillus cereus. These were further studied for amylase production in the presence of starch containing organic substrates such as powdered peels of potato, melon, banana, mango and apple. Solid state fermentations were carried out in mineral salt medium for 24 and 48 h at 37°C. Crude enzyme extract was used for amylase assay to determine the enzyme activity against standard curve of maltose. As a result, banana peel was found to be the best solid organic substrate for the highest alpha amylase production with 331.37, 241.45, 233.12 and 183.17 IU/ml/min in B. subtilis, B. licheniformis, B. cereus and B. mycoids, respectively in 24 h. Melon and potato were next to banana as nutrition, and the level of amylase production in all Bacillus strains with potato peels was comparable to melon peels with slight variations. All strains have shown minimum amylase production with apple or mango peels. A decline in the enzyme activity of the strains was observed after 24 h with all five substrates. Key words: Bacillus, alpha amylase activity, organic substrates, solid state fermentation.