Process optimization for hyper production of xylanase via statistical methodology from isolated Bacillus pumilus 3GAH using lignocellulosic waste

Xylanases hold immense importance in many of the industrial applications for which their economic production at large scale is desired. Isolated xylanolytic strain Bacillus pumilus 3GAH with potential of high titre productivity was selected for subsequent optimization using wheat bran as a substrate. For this, Plackett Burman design was constructed with 11 process variables including media components (wheat bran, peptone, xylose, KNO3 and yeast extract), incubation conditions (shaking conditions, incubation temperature and incubation time), pH, inoculum age and inoculum size. As soon as the most significant factors were identified, they were used to construct Central Composite Design (CCD) within the range of xylose (0.01-0.32 g/50 ml), incubation time (12-26 h), yeast extract (0.01-0.32 g/50 ml), peptone (0.01-0.32 g/50 ml) and temperature (19.7-55.3 °C). CCD predicted the maximum xylanase activity (IU/ml) at the optimum conditions of xylose (0.1 g/50 ml), incubation time (22 h), yeast extract (0.1 g/50 ml), peptone (0.1 g/50 ml) and temperature (30 °C) while the fixed variables were wheat bran (0.3 g/50 ml), KNO3 (0.1 g/50 ml), inoculum size (0.5 ml), inoculum age (16 h) and shaking at 120 rpm. These statistical designs altogether resulted in approximately 1430 IU/ml xylanase activity translating to around 200,200 IU/gds (per gram dry substrate) with 24 fold increase as compared to unoptimised 8310 IU/gds; hence proving its utility.