Ethanol-driven biosynthesis of polyhydroxyalkanoates by a newly isolated wild-type Cupriavidus strain

Ethanol has emerged as an attractive and sustainable feedstock for biomanufacturing because of its high atom economy and direct conversion to acetyl-CoA. However, its use for polyhydroxyalkanoate (PHA) production remains limited by the scarcity of microbial chassis. Here, we report a newly isolated wild-type strain, Cupriavidus sp. ZWJ01, obtained through ethanol-enrichment screening of soil samples collected from Pu'er City, Yunnan, China. This strain exhibits an exceptional innate capacity for ethanol-based PHA biosynthesis. Fermentation profiling under diverse carbon regimes revealed robust ethanol tolerance, sustained growth, and efficient polymer accumulation. After culture optimization, this unengineered strain produced 5.07 g/L poly(3-hydroxybutyrate) (PHB) with a conversion yield of 0.51 g/g ethanol, corresponding to 55% of the theoretical maximum. In addition, co-feeding ethanol with secondary substrates enabled the flexible synthesis of the functional copolymers poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P34HB) with tunable monomer composition. Downstream characterization, including molecular weight analysis, further confirmed the structural integrity and material potential. Collectively, this work highlights ethanol as a highly efficient feedstock and establishes a robust native platform for the sustainable production of diverse high-value PHAs.