Unlocking efficient polyhydroxyalkanoate production by Gram-positive Priestia megaterium using waste-derived feedstocks.

Polyhydroxyalkanoates (PHA) are sustainable alternatives to conventional plastics due to biodegradability and biocompatibility. However, most PHA-producing strains are Gram-negative, which co-produce endotoxins that limit their applicability in high-quality biomedical fields. Additionally, industrial-scale PHA production is hindered by high costs, with feedstocks accounting for half the total expenses. In this study, a Gram-positive strain, GM-4, was isolated and evaluated for industrial potential. This strain achieved a dry cell weight (DCW) of 5.4 g/L and a PHA content of 63% with glucose, exhibiting the highest production rates at the genus level. GM-4 could efficiently utilize sugarcane molasses and corn steep liquor, yielding 13.60 g/L DCW and 9.84 g/L PHA, which represents one of the highest PHA production observed from a wild bacterial strain utilizing waste-derived feedstocks at the flask scale. This feedstock combination significantly enhanced biomass growth and PHA production by 2.6-fold and 3.1-fold, respectively, offering economic and environmental benefits. The produced PHA was determined as polyhydroxybutyrate with excellent material properties through comprehensive characterization. Whole-genome analysis clarified the metabolic pathways that convert diverse substrates into PHA. These findings position GM-4 as a promising candidate for sustainable and cost-effective PHA production, with potential for biomedical and other applications.