Bacillus cereus PHB CMST1: A Potential Halophilic Bacterium for Cost-Effective and Sustainable Production of Polyhydroxyalkanoates

Abstract Bacteria can spontaneously produce polyhydroxyalkanoate (PHA), a thermoplastic and biodegradable substance. PHA is the best polymer substitute for plastic made from petrochemicals. In this investigation, we isolated sixteen bacterial strains from brine and sediment samples collected from a solar salt works facility. Among the sixteen bacterial strains screened for polyhydroxyalkanoate (PHA) production, two strains, Z6 and Z9, exhibited promising results based on Sudan Black B and Nile Blue A staining. Subsequent morphological, biochemical, and molecular characterization identified strain Z9 as Bacillus cereus PHB CMST1 through 16S rRNA sequencing, which demonstrated superior PHA production compared to the other strain. To optimize PHA production, we employed a one-factor-at-a-time (OFAT) methodology, revealing optimal conditions of 35°C, pH 7, 2% salinity, and a 3-day incubation period, utilizing wheat bran as the carbon source and urea as the nitrogen source. Further optimization using Response Surface Methodology-Central Composite Design (RSM-CCD) indicated that B. cereus strain PHB CMST1 requires 5% wheat bran and 2% urea for enhanced PHA synthesis. The yellowish-green dots in the thin layer chromatography (TLC) plate indicated the presence of PHA. FT-IR analysis confirmed that, ????-glycosidic linkages between the sugar monomers were found. The derivatives of polyhydroxybutyric acid confirmed the monomeric polymer by GC-MS analysis. PHA's XRD study showed wide peaks at 20° and 43°, indicating that the PHA had a semi-crystalline structure. Bacillus cereus shows considerable promise for cost-effective and large-scale production of PHA bioplastics, utilizing wheat bran as a non-expensive carbon source.