Screening Isolation Characterization And Production Of Polyhydroxybutyrate _Phb_ By A Bacterium Isolated From Sewage Waste

Abstract

Plastics and polypropylene polymers are synthesized from nonrenewable resources and persist in environment long after intended use, resulting into problems of global environmental pollution. Hence, the present study focused on production of Polyhydroxybutyrate (PHB) microbial polyester by bacterial fermentation. In the present study, PHB producing bacterial species were isolated from sewage waste, Guntur, India. Among all one isolate showed the maximum PHB yield. The high PHB producing bacterium was identified as Acinetobacter nosocomialis RR20, based on biochemical and molecular methods. Further, the characterization of PHB produced from this strain was also studied by analytical methods namely, FT-IR, DTA, TGA, 1H-NMR, 13C-NMR and LC-MS. In this study, different strains of isolated bacteria were evaluated for their PHB productivity, but Acintobacter nosocomialis RR20 strain resulted highest production. Therefore, optimization of process parameters was determined in batch fermentation mode using one-parameter at a time approach and statistical methods for enhanced production of PHB. The influence of physical and chemical variables namely incubation period, temperature, , inoculums size, pH, carbon source, nitrogen source and mineral salts were studied for improving the production of PHB. Maximum PHB was found 4.17 g/L at optimized conditions of incubation period 48 h, temperature 37 oC, pH 7.0, inoculums size of 4 %, molasses 30 g/L, ammonium sulphate 3g/L and 0.3 g/L MgSO4. Further, the modeling and optimization were performed to enhance the production of PHB through submerged fermentation by A. nosocomialis RR20 using Response Surface Methodology (RSM). The effect of process parameters namely molasses (carbon source), ammonium sulphate (nitrogen source), MgSO4 (mineral salt), temperature (oC), pH and incubation time (h) and their combinational interactions on production was studied in shake flask culture by Central Composite Design.