The research was aimed at isolation, characterization and identification of PHB producing organism from soil and optimization of physical and media parameters. Six different soil samples and raw milk was used for isolation of microbes. 76 colonies were isolated. Among these samples, 35 gave positive result for Sudan Black staining. 3 samples namely PSNH1B, SRSNH1B and SRSH2A were selected based on maximum intensity of PHB yield. Optimization of media and physical parameters (pH and temperature) was conducted on these samples. Seven different carbon sources (glucose, fructose, sucrose, lactose, xylose, glycerol and sorbose) were used as carbon source and three nitrogen sources ammonium chloride, potassium nitrate and ammonium phosphate) were used to study the effect of these substrates on PHB yield. PSNH1B showed optimal growth at 37° C while other gram negative strain gave rapid growth at 30°C. pH variation was done from 6.5 to 8.5. No significant variation in growth was observed in samples under study. Cell growth and PHB accumulation was found to be distinctive of isolate type. Gram-positive isolate PSNH1B which was identified as Bacillus thuringiensis gave maximum yield when xylose was used as a carbon source. Glycerol followed by lactose gave maximum yield for gram negative samples SRSNH1B and SRSH2A. All three isolates gave highest yield for ammonium chloride as compared to other nitrogen sources.
