Response surface methodology as an approach for optimization of α-amylase production by the new isolated thermotolerant Bacillus licheniformis WF67 strain in submerged fermentation

Abstract

Abstract In this study, a thermo-tolerant isolated Bacillus licheniformis WF67 has produced considerable levels from the extracellular α-amylase under submerged fermentation conditions. To maximize the α-amylase production, both traditional “one factor per time” and statistical optimization were performed. The “one factor per time” optimization technique declared the most effective parameters in the process of α-amylase production. Those parameters were cultivation medium pH value, incubation time, soluble starch and beef extract as carbon and nitrogen sources. Response surface methodology (RSM) was employed to get the effective values of those most efficient parameters via different interaction ratios between all of them. Central composite design (CCD) was based on the following values: medium pH (pH 3.0–9.0), incubation time (15–75 h), soluble starch (1.5–19.5 g/L), and beef extract (1.0–13 g/L). Results obtained from CCD approach revealed that the incubation of B. licheniformis WF67 for 50 h, at pH value of 6.33, using the specified medium containing 12.55 g/L soluble starch, and 8.31 g/L beef extract were the optimum values for α-amylase production. Under the previously mentioned conditions α-amylase productivity was improved by about 90% (6.633 U/mL) in comparison to the traditional “one factor per time” optimization results (3.486 U/mL).