Optimisation of experimental variables for extracellular amylase production by Bacillus cereus AS2

Amylases are one of the biotechnologically important enzymes that have multiple applications in the food, pharmaceutical, cosmetics, textile, detergent, paper and pulp, bioremediation and nano-biotechnology industries. Amylases can be isolated from animals, plants and microbial regions, but nowadays enzymes from prokaryotic species have gained more importance. Among the microbes, amylases from Bacillus cereus have gained considerable demand in various industrial sectors. Growing industrial demand for enzymes compels the availability of enzymes in large quantities that can only be achieved by employing efficient fermentation techniques. Therefore, the current study is aimed at the statistical optimisation of the production conditions for extracellular amylase production from Bacillus strain AS2. In a recent study, the optimum amylase producing AS2 strain was identified on a molecular level, and it was found that it has close relation with the already reported strains of Bacillus cereus. The further enzyme production was optimised by using a statistical optimisation tool. A full-factorial central composite design (CCD) consisting of 53 experiments was designed using six significant variables (incubation period, pH, temperature, carbon and nitrogen source and metal ion). The analysis revealed that the optimal media concentrations were 54.34 g.L-1 starch, 0.63 g.L-1 CaCl2, 1 g.L-1 glycine, pH 7.0, 76 h, and 40 °C, respectively. A 1.23-fold increase in the enzyme yield (1 050 IU.mL-1.min-1) was noticed as compared to the original production level. The statistical optimisation approach gives the exact variables that influence the enzyme production and, hence, offers the best way to optimise the bioprocess. The optimised enzyme can be used in industries for various purposes such as de-sizing, de-inking, hydrolysing starch residues, etc.