Production of PHB (Poly-Beta-Hydroxybutyrate) in Bacillus subtilis cultures

Environmental pollution due to plastic wastes is an emerging problem of the world. The use of novel biodegradeable plastics is currently seen as a solution to overcome this problem and poly-ß-hydroxybutyrate (PHB) polymer is a well-known bioplastic agent. Many organisms accumulate PHB granules as carbon and energy sources under stress.There has been an increase in the number of researchers working on PHB-producing microorganisms in recent years. PHB has many advantages compared to petroleum-based plastics, which facilitate its use in many fields of industry.In the present study, our aim was to assess the PHB productivity of Bacillus subtilis ATCC 6633 strain under different conditions. The amount of PHB production was measured by UV-VIS spectrophotometer at 235 nm. The effects of incubation time (2-30 hours), temperature (20, 25, 30, 35 and 40 0C), pH (5.0, 6.0, 7.0, 8.0 and 9.0), carbon sources (glucose, sucrose, D ?mannitole, arabinose), nitrogen sources (protease peptone, L-glycine, L-cystein, ammonium sulfate and potassium nitrate) and the rate of carbon/nitrogen ratio (0.5, 1, 1.5, 2, 2.5) on PHB synthesis were all assessed in the study.According to the results of the study, the highest PHB production was obtained after 24 hours of incubation (10.4981 µg/ml), at 7.0 of pH (10.4981 µg/ml), with D-mannitole (23.6623 µg/ml) as carbon source, L-glycine (14.6217 µg/ml) as nitrogen source, C/N ratio of 2.5 (3.2481 µg/ml) and with a temperature of 30 0C in culture media (10.4981 µg/ml).Although PHB production is relatively an expensive method with Bacillus subtilis ATCC 6633 strain, nature-friendly bioplastics such as PHB will probably gain popularity with more efficient strains or microorganisms and/or cheap substrates.Keywords: Bacillus subtilis, carbon and nitrogen sources, Poly-ß-hydroxybutyrate (PHB), PHB (bioplastic) production