Sustainable Valorization of Sugarcane Molasses into Polyhydroxybutyrate by Pseudomonas plecoglossicida MK-6 and Optimization Using Response Surface Methodology

Polyhydroxybutyrate (PHB), is a sustainable, and green alternative to petrochemical plastic, however, its production cost remains high due to reliance on glucose. This study was designed to screen PHB producing bacteria from dumping soil to evaluate PHB production using agro-industry waste of sugarcane molasses as carbon source in reference to an efficient waste recycling practice. The PHB positive strain GSBB-5a2-2 was screened by using Sudan Black B and Nile Blue A and was identified as Pseudomonas plecoglossicida MK-6 based on 16S rRNA sequencing (GenBank accession number OQ236410), was selected for further analysis. The ideal fermentation variables were determined using single factor optimization, the maximum PHB (7.8 g/L) was obtained with 5% sugarcane molasses, ammonium sulfate as a nitrogen source, 8:1 C/N ratio, pH 7, 37°C and 150 rpm for 48hrs were found as optimum factors. Further optimization using Response Surface Methodology with Box-Behnken Design enhance PHB synthesis. The extracted PHB was identified via Fourier transform infrared spectroscopy (FT-IR). PHB production by Pseudomonas plecoglossicida MK-6 has been previously documented; however, this study reports for the first time to optimize PHB synthesis by this strain using sugarcane molasses as a low-cost carbon substrate, contributing to circular bio economy goals.