Production of polyhydroxyalkanoate from new isolated bacteria of Acidovorax diaphorobacter ZCH-15 using orange peel and its underlying metabolic mechanisms.

Polyhydroxyalkanoate (PHA) is considered a sustainable alternative to traditional petroleum-based plastics due to its biodegradability and biocompatibility. In this study, Acidovorax diaphorobacter ZCH-15, an efficient PHA-producing strain, was isolated from activated sludge. Using food waste-derived orange peel as a substrate, the strain initially achieved a PHA concentration of 0.39 g/L. Under optimal fermentation conditions (30℃, pH 8, 2 % inoculum concentration, and 30 g/L carbon source), the PHA concentration increased by 138 % to reach a maximum of 0.93 g/L. Proton nuclear magnetic resonance spectroscopy and gas chromatography analyses identified the PHA composition as poly(3-hydroxybutyrate-co-3-hydroxyvalerate), which exhibited high crystallinity and structural stability. Metabolomic analysis indicated that the tricarboxylic acid cycle and pentose phosphate pathway were involved in producing succinyl-CoA, a precursor required for PHA synthesis. This study demonstrates the potential for cost-effective industrial PHA production while enabling the high-value utilization of food waste.