Optimization and production of polyhydroxybutyrate from sludge by Bacillus cereus categorized through FT-IR and NMR analyses

Abstract

This study was designed to isolate polyhydroxybutyrate (PHB) producing bacteria from Hosur lake soil and optimize the suitable growth conditions and supplementary factors for PHB production. Totally, 15 bacterial cultures were enumerated from lake soil, out of fifteen, one isolate was recognized as PHB producer based on Sudan Black B staining along with PHB selective media. The PHB positive isolate was identified as Bacillus cereus by standard biochemical and 16S rRNA analyses. The produced PHB was studied by Fourier transform infrared spectroscopy (FR-IR) and Proton nuclear magnetic resonance (1H NMR) analyses. The signal band for the PHB compound was noticed at 1633.71 cm−1 on FT-IR analysis. Three signals were recorded as 2.55, 2.372, and 3.389 ppm on 1H NMR analysis and these were analogous of the methylene group, methyl group, and methine group, correspondingly and these factors are polymeric representatives of PHB. The suitable growth conditions and factors for B. cereus were optimized as 10% of inoculum, at 35 °C, pH 7.5, 2 g L−1 of yeast extract, rice bran 20 g L−1, and 48 h of incubation for production of PHB. Under these optimized circumstances, B. cereus produced 90.80% of PHB as 32.78 g L−1 of PHB from 38.54 g L−1 of biomass. Finally, the results concluded that the isolated B. cereus would be a suitable candidate for viable PHB fabrication due to its low-cost substrate consuming potential and minimal cost of production.