Enhancing Biological CO to Formate Conversion: Application of Aerophobic Coatings to Mitigate Bubble Coalescence

Biological carbon monoxide (CO) conversion to formate is hindered by gas-liquid mass transfer limitations due to bubble coalescence, which reduces the interfacial area for gas exchange. In this study, we introduce a novel approach by applying an aerophobic coating to a perforated baffle in an airlift bioreactor. This aerophobic coating prevents bubble coalescence, thereby enhancing mass transfer efficiency and increasing the conversion rate of CO to formate. First, we confirmed that in enzymatic reactions, the mass transfer rate of CO gas determines the maximum productivity under optimal conditions. We optimized the aerophobic coating conditions for the perforated baffle to achieve effective bubble breakage. By installing the aerophobic-coated perforated baffle with optimized coating conditions into the reactor, we promoted efficient bubble breakage, reduced bubble size, and increased gas-liquid mass transfer coefficients. This resulted in the maximum volumetric productivity of 60.4 mM/h in CO-to-formate conversion, a 72% increase over the bioreactor without a coated baffle. This significant improvement demonstrates the effectiveness of aerophobic coatings in enhancing gas-liquid mass transfer, providing a new strategy to increase efficiency and scalability in the biological gas conversion industry.