Optimization of Polyhydroxybutyrate (PHB) production by locally isolated Bacillus aryabhattai using response surface methodology

In the present study, an attempt was made to isolate an efficient Polyhydroxybutyrate producing bacterium from soil. A total of 38 different types of bacteria were isolated, out of which 15 were found to be PHB positive, based on the viable colony staining method of screening using Nile red Dye. The isolate (6N) showed maximum PHB production of 0.17 g/L, and PHB produced was confirmedusing NMR. The most potent isolate (6N-NRC) was identified using 16S rRNA, and phylogenetic analysis clearly demonstrated that the strain 6N-NRC is a member of the genus Bacillus and is identified as Bacillus aryabhattai. The culture medium and growth parameters were optimized using one factor at a time, multifactorial experimental design (Plackett-Burman and Box-Behnken) and utilization of Beet molasses as cheap and economic carbon source for maximum PHB production was done. Beet molasses (30 g/L) as the carbon and ammonium chloride (0.75 g/L) as the nitrogen source were found to be the best nutritional sources for maximum PHB production. Incubation time period 36h, pH of the medium at 8.0 and temperature of 30°C were found to be optimum conditions for obtaining maximum PHB yield of 3.799 g/L.