Poly(3-hydroxybutyrate) production from swine wastewater and waste vegetable oil by Cupriavidus necator in nonsterile bioreactors.

Swine wastewater (SW), rich in nitrogen and phosphorus, and waste vegetable oil (WVO) are abundant feedstocks with potential for microbial biopolymers production. However, high polyhydroxyalkanoates (PHA) yields under nonsterile conditions remain challenging due to inhibitory compounds and microbial competition. Here, we cultivated Cupriavidus necator DSM545 under nonsterile conditions with varying SW dilutions combined with WVO for PHA synthesis. Batch bioreactors containing two-thirds (v/v) non-centrifuged wastewater yielded the highest polyhydroxybutyrate titers of 6.8 ± 0.1 gPHB/L, with C. necator comprising over 80% of the microbial community. A nonsterile fed-batch reactor further enhanced PHB titers by 10-fold, reaching a volumetric productivity of 1.37 gPHB/L⋅h, where Cupriavidus dominated the community (>98%). The produced PHB exhibited a melting temperature of 170 °C, molecular weight of 437 KDa, and a polydispersity index of 2.1. These findings demonstrate that C. necator can outcompete native microorganisms in wastewater and convert nutrient-rich waste streams into bioplastics.