Transforming greenhouse gases into protein powerhouses: Hollow fiber membrane bioreactors for efficient CO2 bioconversion.

Gas fermentation offers a promising approach for converting waste and greenhouse gases into valuable products. Hydrogen-oxidizing microbes like Cupriavidus necator can fix CO2 into single-cell protein (SCP) using H2 under aerobic conditions, but low gas solubility in aqueous media limits productivity. To address this, a hollow fiber membrane bioreactor (HFMB) was integrated with Cupriavidus necator H16 for SCP production via aerobic CO2 bioconversion. Compared to bubble column (BCB) and microbubble column bioreactors (MCB), the HFMB's high gas permeability significantly improved gas dissolution, enhancing bacterial growth (3.15-6.83 folds) and amino acid production (up to 281.11 %). Optimal conditions, including higher gas flow rates (187.5 mL/h) and temperature (40 °C), further increased SCP yields by over twofold in the HFMB. Additionally, HFMB demonstrated the ability to operate continuously with stable SCP production and less membrane fouling. This study underscores the promise of membrane technology for advancing SCP production via gas fermentation.