<span style="font-size:15.0pt;font-family:"Times New Roman";mso-fareast-font-family: "Times New Roman";mso-bidi-font-family:Mangal;mso-ansi-language:EN-GB; mso-fareast-language:EN-US;mso-bidi-language:HI" lang="EN-GB">Medium optimization for pullulanase production from <i style="mso-bidi-font-style:normal">Anoxybacillus</i> species using experimental design</span>

Abstract

The aim of the present study was to improve pullulanase production from the thermophilic <i style="mso-bidi-font-style: normal">Anoxybacillus </i>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 <i style="mso-bidi-font-style: normal">p</i>H, 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 <i style="mso-bidi-font-style:normal">p</i>H 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 <i style="mso-bidi-font-style:normal">Thermus</i> medium.