Statistical optimization of alpha-amylase production by Streptomyces erumpens MTCC 7317 cells in calcium alginate beads using response surface methodology

α-Amylase has a wide range of applications in starch industries, i.e. baking, brewing, distillery, etc. The α-amylase production from Streptomyces erumpens MTCC 7317 immobilized cells was compared with that of free cells. The immobilized cells of S. erumpens in calcium alginate beads were more effective for production of α-amylase (12.2% more yield) than free cells. Response surface methodology (RSM) was used to evaluate the effect of main variables, i.e. incubation period, pH and temperature on enzyme production with immobilized cells. A full factorial Central Composite Design (CCD) was applied to study these main factors that affected α-amylase production. The experimental results showed that the optimum incubation period, pH and temperature were 36 h, 6.0 and 50°C, respectively for immobilized cells. Repeated batch fermentation of immobilized cells in shake flasks carried out in starch-beef extract medium showed that S. erumpens cells were physiologically active on the support even after four cycles of fermentation.