Characterization and Optimization Studies on Poly[(R)-3-Hydroxybutyrate] Producing Moderately Halotolerant Bacterial Strains Isolated from Saline Environment

Objective:
The objectives of this study were to isolate Poly[(R)-3-Hydroxybutyrate] (PHB) producing halotolerant bacterial strains from a saline environment and optimize the various growth conditions of the isolates for the maximum production of PHB. The isolated bacterial strains were then identified based on morphological, biochemical and molecular characteristics.
Materials and methods:
Halotolerant PHB-producing bacterial strains were isolated from saline environment in a nitrogen deficient medium containing 3% Sodium chloride. Following isolation, the strains were screened for PHB production by primary and secondary screening techniques and further confirmed by FTIR analysis. Optimization studies were performed to determine the effect of various carbon and nitrogen sources, different salt concentrations, temperature and pH for the maximum production of PHB. The PHBproducing isolates were then identified by biochemical and molecular characterisation.
Results:
Fifteen different strains of bacteria were isolated from the soil sample collected from Pulicat lake, a saline lake near Chennai. Out of the isolates that that were screened positive for both Sudan Black B staining and Nile Blue A staining methods, four potential PHB- producing bacterial strains were identified by FTIR analysis. The amount of PHB produced by the isolates SNKVG-16, SNKVG-17, SNKVG-20 and SNKVG-22 are 31, 42, 39 and 49 mg/ 100 mL respectively. The four bacterial strains were biochemically characterized and molecularly identified as Roseivivax lentus, Bacillus toyonensis, Klebsiella quasipneumoniae subsps. and Bacillus marcorestinctum.
Conclusion:
Halotolerant organisms are potential sources of PHB as they do not require strict sterile conditions and has relatively simple extraction process. The biodegradable nature of PHB makes it a suitable substitute for conventional plastics. It has potential applications in medicine, agriculture, material sciences and so on.