Optimization of medium components using response surface methodology for production of thermostable amylopullulanase in submerged fermentation by Clostridium thermosulfurogenes SVM17

Response surface methodology (RSM) based on central composite rotatable design (CCRD) was used to determine the optimal levels of medium components, viz., soluble starch, tapioca flour, peptone, magnesium chloride and ferrous sulphate for enhanced thermostable amylopullulanase production by Clostridium thermosulfurogenes SVM17 in submerged fermentation. The design contains a total of 54 experimental trials with first 32 organized in a fractional factorial design and experimental trials from 33-40 and 51-54 involving the replication of the central points. Within the tested range of concentrations, all medium components were found significant. The optimum levels of nutrients for maximum production of enzyme were (% w/v): potato starch, 5.2; tapioca flour, 6.3; peptone, 2.5; MgCl2·6H2O, 0.015 and FeSO4·7H2O, 6.0 ppm. After optimization of medium components, the strain SVM17 showed 96 and 409 % increased amylase and pullulanase activities, respectively when compared with the non-optimized conditions.