Medium optimization for pullulanase production from anoxybacillus species using experimental design

Abstract

The aim of the present study was to improve pullulanase production from the thermophilic Anoxybacillus species strain SK3-4 by medium engineering. The strain was isolated from a Malaysian hot spring, Sungai Klah (SK). The optimization processes were performed in two stages using 24 full factorial design and central composite rotatable design (CCRD). Four variables were manipulated to improve pullulanase yield: initial culture pH, and concentrations of pullulan, tryptone and ammonium chloride by using a 24 full factorial design. Following that a quadratic model of CCRD was then used to identify the optimum yield of pullulanase by manipulating all four of these significant parameters. The optimized medium composition was a pH of 8.29, 0.79% (w/v) pullulan, 0.12% (w/v) tryptone and 0.39% (w/v) ammonium chloride, giving a final pullulanase activity of 3.86 U/mL and specific activity of 3.38 U/mg. The specific activity achieved was higher than the CCRD predicted value (3.00 U/mg). The application of two different experimental designs resulted in an improvement of pullulanase specific activity of approximately 73% from the original Thermus medium