Optimization, Production and Characterization of Polyhydroxyalkanoate (PHA) from Indigenously Isolated Novel Bacteria

Synthetic plastics have multiple applications in modern world. However, being non-degradable in nature, these have turned into environmental pollutants. Natural ecosystem and global biodiversity are facing serious challenges due to the plastic pollution. Effective degradation and replacement of synthetic plastics with natural and ecofriendly biomaterial is crucial. Polyhydroxyalkanoates (PHAs) are the microbial polyesters and have great potential as biopolymers for the development of bioplastics. PHA produced and accumulated as granules in the cytoplasm of various microbes under limited supply of nutrients can serve the purpose of bioplastic production. Biosynthesis of PHA using bacteria needs well-optimized nutrient and growth conditions for which, studies optimizing the parameters of bacterial growth using various carbon and nitrogen sources are required. Current study optimized the production of PHA by two indigenously isolated strains of Pseudomonas sp. AK-3 and AK-4. The strain AK-3 produced 1.08 g/L of PHA with a yield of 54.82% in the presence of 2% sucrose as carbon source and 1% of (NH4)(2)SO4 as nitrogen source (C/N ratio of 4:1). The yield, however, reduced to 7.73% when 2% (NH4)(2)SO4 was added as a nitrogen source in the production medium (C/N ratio of 4:2). Pseudomonas sp. AK-4 produced 0.92 g/L of PHA with a yield of 43.80% for 2% sucrose as carbon source. Addition of 1% (NH4)(2)SO4 had negligible effect on the yield. Considerable increase in cell dry mass was observed when high concentrations of various carbon sources were used. Biosynthesis of PHA was declined when 1% concentrations of nitrogen sources such as ammonium chloride (NH4Cl), ammonium nitrate (NH4NO3) and ammonium sulphate (NH4)(2)SO4 were used. The optimum temperature and pH for production of PHA were found to be 38 degrees C and 8.0 respectively, with an optimum incubation period of 72 h. FTIR results of the extracted polyesters showed transmittance peaks at wavenumbers of 1725 cm(-1), 1375 cm(-1), 1278 cm(-1), 1132 cm(-1), 1054 cm(-1) and 977 cm(-1). Based on FTIR analysis it was concluded that the polyester produced by both Pseudomonas sp. AK-3 and AK-4 was poly-3-hydroxybutyrate P(3HB).