Optimization of Independent Variables for the Production of Extracellular Alpha Amylase by Bacillus subtilis IMD34 Using Plackett-Burman Design

Abstract

Bacillus species are widely used for thermostable α-amylase production for various applications such as in the detergent and food industries. This research aimed to study the production of α-amylase by B. subtilis IMD34 in submerged fermentation conditions using Plackett-Burman (PB) design, along with the optimization of certain environmental factors for optimal growth of amylolytic bacteria. Plackett-Burman design was used to evaluate the effect of ten independent variables on α-amylase production. Maximum enzyme activity was recorded in a medium containing (g/l); starch (6.0), peptone (12.0), K₂HPO₄ (1.0), Na₂HPO₄ (2.0), NaCl (0.6), Na₂SO₄ (0.1), MgSO₄.7H₂0 (1.0), FeCl₃.6H₂O (0.02), CaCl₂.2H₂O (0.02) and with an agitation speed (200 rpm). From the pareto chart it was observed that the most important independent variables for amylase production were starch, peptone, NaCl, Mg₂SO₄, CaCl₂.2H₂O and agitation. Optimization of environmental parameters to assess their effect on the growth of bacteria showed that optimal pH, incubation time and temperature were recorded at 6, 48h and 37˚C. Evaluating independent variables statistically using PB design revealed that some of the medium’s components had a positive impact on α-amylase production by B. subtilis IMD34.