Media Optimization of Bacillus thuringiensis PBT-372 Using Response Surface Methodology

S. R. Prabagaran, K. Pakshirajan, T. Swaminathan and S. Jayachandran

Abstract
Statistical design of experiments, to determine the optimal levels of the sugar concentration from molasses, initial pH of the medium and the inoculum for the production of Bacillus thuringiensis in shake flask fermentation, was used. Initial screening of locally available raw materials viz. fish meal, molasses, sago, paddy straw and whey for maximizing biomass and pesticidal crystal protein (PCP) production from B. thuringiensis was performed. Optimized values of 4.19 % of inoculum, initial pH of 5.62 and 11.9 g L–1 of molasses resulted in higher biomass and PCP production. Using response surface methodology, good interactions between these factors were found to be present in optimizing the biomass yield. Among the interactions between these factors, the one between pH and sugar concentration was the most significant.

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Keywords
Bacillus thuringiensis, pesticidal crystal protein, response surface methodology, microbial insecticide