Production of α-amylase using new strain of Bacillus polymyxa isolated from sweet potato

Abstract

In this study, a new amylase producer strain was isolated from sweet potato tuber. This strain was able to grow at 37 °C and produce α-amylase in high quantity compared to other standard strain cultures. In the first part, cultivation in shake flask in standard medium was carried out to give complete information about the growth and production kinetics of this strain. The results clearly demonstrate that the isolated strain is able to production α-amylase in submerged culture with concentration up to 2050 kat/L after 20 h cultivation. Furthermore, medium optimization was carried out by changing the starch concentration and cell cultivation in medium of mixed carbon source (composed of starch and glucose of ratio 15:5 g/g) to enhance the production process and to increase the growth rate. The volumetric and specific α-amylase production in this optimized medium were 4550 kat/L and 1060 kat/g, respectively. Further improvement in enzyme production process was achieved by scaling up the process from shake flask to 3-L stirred tank bioreactor under non-oxygen limiting condition. The maximal volumetric and specific α-amylase productions in bioreactor batch culture were 5210 kat/L and 1095kat/g, respectively, after only 14 h cultivation.