Optimization of enzymatic saccharification of pretreated sugarcane bagasse for enhanced polyhydroxybutyrate (PHB) production by Bacillus megaterium PNCM 1890

Polyhydroxyalkanoates (PHAs) are microbial polyesters that serve as biodegradable and bio-based alternatives to conventional plastics. Using renewable feedstocks, such as lignocellulosic biomass, offers a sustainable approach to PHA production while mitigating petrochemical dependence and plastic waste accumulation. In this study, enzymatic saccharification of sequentially pretreated sugarcane bagasse (SCB) was optimized to maximize hydrolysate yield for polyhydroxybutyrate (PHB) fermentation. Key parameters—solids loading, enzyme loading, and saccharification time—were evaluated for their impact on reducing sugar yield (RSY). A numeric factorial experiment confirmed their significant effects, and response surface methodology with a face-centered central composite design was employed. ANOVA results revealed the significance of the main and quadratic effects of these factors on RSY. Optimization identified ideal conditions as 4.94 % (w/v) solids loading, 102.98 filter paper units (FPU)/g dry biomass enzyme loading, and 70.44 h of saccharification, yielding 0.46 g reducing sugar/g dry biomass. Fermentation of the optimized hydrolysate achieved a maximum PHB concentration of 6.11 g/L after 20 h, with glucose consumption exceeding xylose. These findings provide a foundation for local bioplastic production using sugarcane bagasse.