Polyhydroxybutyrate (PHB) is biodegradable polyester produced in nature by microbial fermentation and it is used as thermoplastic. Azotobacter vinelandii is a bacterium that accumulates PHB as intracellular granules in response to physiological stress such as excess of carbohydrate sources and limitation of nutrients e.g. nitrogen, oxygen and phosphorus etc. PHB produced in this work have great potential be used in various industries like pharmaceutics and food industry for packaging purposes and medical field. Recent research work was conducted to produce PHB form cheap agro industrial wastes like Molasses and Whey by fermentation. Different parameters such as substrate water ratio, incubation period, volume of inoculums and pH were optimized for maximum yield of PHB.
In this study fermentation media containing whey and molasses as substrates was used to check the production of PHB from the Azotobacter vinelandii. 0.5ml of inoculum media was taken in fermentation media and then kept for incubation for 24-72 hours. After incubation, culture media was centrifuged and then sediment was used for extraction, determination and identification of PHB.
It was found that Azotobacter vinelandii in molasses contained medium gives maximum yield of PHB (mg/100mL) at 4% substrate water ratio after 48 hours of incubation period (140 mg/100mL), at 2.5 mL of volume of inoculum (204 mg/100mL), at pH 8.0 (220 mg/100mL), at 0.2% of peptone (252 mg/100mL) and 0.25% (234 mg/100mL) of yeast extract. While 4% of substrate water ratio after 60 hours of incubation (128 mg/100mL), 2.0 mL of volume of inoculum (176 mg/100mL), pH 7.0 (192 mg/100mL), 0.25% of peptone (248 mg/100mL) and 0.25% of yeast extract (240 mg/100mL) were observed to be optimum parameters for maximum production of PHB from Azotobacter vinelandii in whey based medium. Data was analyzed by means of linear regression analysis to determine R (regression coefficient), which was used to find significant differences (P?0.05) in each experiment.
Conclusion: The results of present study show that molasses and whey are economically good substrates for production of polyhydroxybutyrate (biodegradable polymer) from Azotobacter vinelandii. The results also suggest that Azotobacter vinelandii is a good potential strain for production of PHB under optimized conditions.