Valorization of Dried Okara Hydrolysate for Polyhydroxybutyrate Production by Newly Isolated Burkholderia sp. EP10

Dried okara (DOK), a lignocellulosic byproduct from tofu production, was evaluated as both a carbon source and culture medium to enable cost-effective polyhydroxybutyrate (PHB) production. Hydrolysis with either HCl or H₂SO₄ generated 48-51 g/L reducing sugars with peak values reaching 60.2 g/L using 3% acid at 121 °C. Analysis of monosaccharides indicated pentoses, especially xylose, as the main sugars present. A novel strain, <i>Burkholderia</i> sp. EP10 exhibited direct growth and PHB accumulation in DOK hydrolysate without requiring detoxification, tolerating inhibitory compounds such as furfural and 5-hydroxymethylfurfural. In shake flask experiments, the strain achieved 6.9 g/L biomass and 26.3 wt% PHB, while in fermentor studies, biomass reached 10.9 g/L and PHB content was 29.3 wt% at a C/N ratio of 5.7. Notably, these outcomes were achieved without pH control, constituting a key benefit for operational simplification and cost minimization. The biopolymer was verified as PHB using gas chromatography, Fourier transform infrared spectroscopy, and proton nuclear magnetic resonance spectroscopy. The PHB displayed melting transitions at 163.5 and 172.4 °C, a degradation onset at 268 °C, and high molecular weight (4.66 × 10⁵ Da). <i>Burkholderia</i> sp. EP10 for sustainable PHB production via direct bioconversion of lignocellulosic hydrolysates, without the need for pH adjustment, detoxification, or complex medium development.