Optimization of Polyhydroxyalkanoate Production Using Bacillus Cereus Isolate: a Response Surface Methodology Approach

Polyhydroxyalkanoates (PHAs) are biodegradable, biocompatible polyesters synthesized by bacteria as energy reserves under nutrient-limited, carbon-rich conditions. Despite their industrial potential, high production costs—driven by expensive substrates and suboptimal fermentation limit scalability. Cost-effective PHAs production requires efficient microbial strains and low-cost carbon sources. This study explored PHAs synthesis using a Bacillus cereus isolate, identified via biochemical tests and 16S rDNA sequencing. Corn bran, an abundant agro-industrial waste, served as an economical carbon substrate. Fermentation conditions (pH, temperature, incubation time, substrate concentration, and agitation rate) were optimized using Response Surface Methodology (RSM), a statistical approach for process enhancement. PHAs extraction involved sodium hypochlorite digestion and solvent purification, with characterization via UV-Visible spectrophotometry and crotonic acid assay. ANOVA validated the RSM model, and 3D response plots revealed variable interactions affecting yield. Optimized conditions significantly boosted PHAs production compared to unoptimized methods, proving RSM’s effectiveness. By combining low-cost substrates with statistical optimization, this study addresses key challenges in PHAs biosynthesis. The results support industrial scalability and broader biotechnological applications of microbial PHAs, advancing eco-friendly polymer production. The highest yield (3.902 g/L) was obtained at a substrate concentration of 11 g, pH 9, temperature 31°C, agitation rate of 125 rpm, and an incubation period of 48 hours.