Poly-ß-hydroxybutyrate (PHB) is a biodegradable intracellular microbial product produced by many bacteria and it is comparable to some of the petrochemical derived thermoplastics such as polypropylene. One of the main barriers for the commercial exploitation is the high cost of the substrate for the production of biopolymer. The utilization of mixed microbial cultures facilitates the use of complex substrates thereby reducing the cost of PHB production. In the present study, mixed culture systems were evaluated for PHB production. Bacillus firmus NII 0830 was used for the production of PHB since it accumulates a large amount of PHB and a second organism Lactobacillus delbrueckii NII 0925 was used to provide lactic acid. FTIR and 1H NMR analyses revealed that the PHB extracted from pure culture and mixed culture showed exact match to that of standard PHB. Biodegradation studies of the PHB blends showed 87% degradation. It was also found that a consortium of organisms degraded the films faster than a single organism.

The aim of this work was to study the production of poly-3-hydroxybutyrate (PHB) under nitrogen limited conditions by Bacillus sphaericus NII 0838 using crude glycerol from biodiesel industry as sole carbon source. Effect of various process parameters on PHB production such as glycerol concentration, inoculum size and pH of the medium were optimized. Characterization of extracted PHB was carried out by FT-IR, ¹H and 13C NMR. Results showed that the bacterial culture accumulated about 31% PHB in crude glycerol medium. The extracted PHB was blended with other polymers to improve its physical characteristics. The thermal properties of the polymer like melting temperature (Tm) and heat of fusion (ΔHf) were determined using DSC.