Heterogeneous Catalyst–Microbiome Hybrids for Efficient CO-Driven C6 Carboxylic Acid Synthesis via Metabolic Pathway Manipulation

The synthesis of medium chain carboxylic acids (MCCAs) from syngas provides a promising route for converting coal/organic waste/natural gas into high value-added chemicals. However, neither purely chemical synthesis methods nor purely biological approaches seem poised to realize the potential of syngas-to-MCCAs. Hereby, we developed a hybrid approach and created an alternative pathway for C1 chain elongation to C6, where we combined the efficient carbon fixation of heterogeneous catalysts with the high specificity, low cost, and self-adaptation of anaerobic microbiomes. In the hybrid system, inorganic carbon fixation into organic carbon (adsorbed pyruvic acid) was accomplished by the heterogeneous Pt/Fe2O3 catalysts, and the adsorbed pyruvic acid was subsequently metabolized by the anaerobic microbiome. This hybrid system significantly improved CO conversion and n-caproic acid production (6600 mg COD/L), which was 50–190% higher than that observed in previous studies. The interactions were revealed by macro-omics and in situ diffuse reflectance infrared Fourier transform spectroscopy, demonstrating a manipulated inorganic carbon-to-chemical fixation route.