Two-stage biorefinery strategy using Rhodopseudomonas harwoodiae KKU-NM3/1-2 for biohydrogen production and dairy...

To address the dual challenges of sustainable energy production and agro-industrial waste management, this study presents a novel two-stage biorefinery strategy for the valorization of dairy farm effluent (DFE) using Rhodopseudomonas harwoodiae KKU-NM3/1-2. In Stage 1, an active hydrogen-producing culture was developed using low-cost carbon sources; vinegar was identified as the most cost-effective substrate, yielding 559 mL H₂/L at 87 % purity and a 7.4-fold cost advantage. In Stage 2, the post-biohydrogen production culture was reutilized as a biocatalyst for DFE treatment, achieving an 87 % reduction in chemical oxygen demand (COD). To the best of our knowledge, this is the first report on the application of R. harwoodiae KKU-NM3/1-2 for high-strength DFE remediation. In addition, value-added products, including biomass (2.30 g/L) and carotenoids (1.04 mg/L), were generated, highlighting the process's biorefinery potential. This integrated approach offers a promising model for simultaneous wastewater treatment and resource recovery.