Production of thermostable pullulanase by Clostridium thermosulfurogenes SV2 in solid-state fermentation: optimization of nutrients levels using response surface methodology

The optimization of nutrient levels for the production of thermostable pull ulanase by Clostridium thermosulfurogenes SV2 in solid-state fermentation ( SSF) was carried out using response surface methodology based on the centra l composite rotatable design. The design contains a total of 54 experimenta l trials with the first 32 organized in a fractional factorial design and e xperimental trials from 33-40 and 51-54 involving the replication of the ce ntral points. The design was employed by selecting potato starch, magnesium chloride, ferrous sulfate, corn steep liquor and pearl millet flour as mod el factors. Among the five independent variables studied, except magnesium chloride, all the nutrients were found significant. 16.5% potato starch, 2. 5% corn steep, 0.015% ferrous sulfate and 14% pearl millet flour have been found optimal for the production of thermostable pullulanase. The strain SV 2 produced 10% more pullulanase in the nutritionally optimized solid-state fermentation medium containing only four nutrients.