Agro-Industrial Waste Valorization for Sustainable PHBV Production from Sugarcane Bagasse Using Bacillus sp. HLI02

The large-scale production of microbial bioplastics remains limited by high production costs, reliance on refined substrates, and inefficient utilization of agro-industrial residues. Although sugarcane bagasse has been explored as a carbon source for polyhydroxyalkanoate production, studies have predominantly focused on poly (3-hydroxybutyrate) (PHB), with limited reports on copolymer synthesis from pentose-rich lignocellulosic streams. In this study, a newly isolated Bacillus sp. HLI02 was employed for the biosynthesis of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), using pentosan-rich sugarcane bagasse hydrolysate as an inexpensive and sustainable carbon source. Fermentation parameters were systematically optimized at different pH and temperature, and the strain demonstrated efficient conversion of xylose-rich hydrolysate into PHBV without the requirement for external nutrient supplementation. Under optimized conditions (pH 7.0, 37 °C, and C/N ratio of 40), a maximum PHBV yield of 2 g/L, corresponding to 59.5% of cell dry weight, was achieved. Structural and compositional analyses using Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and 1H and 13C nuclear magnetic resonance (NMR) spectroscopy confirmed successful PHBV copolymer formation with well-defined structural characteristics. Thermal analysis revealed a decomposition temperature of 166 °C, indicating good thermal stability. The produced PHBV further exhibited favourable biocompatibility and biodegradability, supporting its potential applicability in sustainable packaging and related sectors. This work demonstrates the effective conversion of hemicellulosic sugarcane bagasse hydrolysate into PHBV using a newly isolated Bacillus strain, highlighting an underexplored route for copolymer production from agro-waste–derived C5 sugars. By integrating low-cost feedstock utilization with process optimization and comprehensive polymer characterization, this study contributes to the development of economically viable and sustainable bio-based polymer production strategies.