The synergistic effect of formate dehydrogenase and carbonic anhydrase accelerates the ethanol fermentation process and improves carbon recovery

Abstract

Bioethanol is a significant product in the two-carbon strategy, but the CO₂ generated during ethanol fermentation incurs substantial carbon losses. To tackle this issue, we explored a prospective dual-enzyme approach, using formate dehydrogenase (FDH) and carbonic anhydrase (CA), aiming to convert CO₂ to formate in situ, transforming the process from carbon-neutral to carbon-negative. TsFDH was selected among four FDH candidates due to its high enzymatic activity. To overcome the low solubility of CO₂, CA was co-expressed with FDH, facilitating CO₂ hydration. The recombinant strain S. cerevisiae-tsfdh-ca efficiently converted CO₂ to formate and exhibited rapid glucose consumption, which produced 76.3 mg L⁻¹ formate during fermentation, with a 69% increase in the glucose fermentation rate and a 108% increase in formate yield. Additionally, it reduced CO₂ emissions significantly, and the ratio of CO₂ release and ethanol production decreased from 1.89 to 1.39. The dual-enzyme system, FDH/CA, as elucidated by transcriptomic analysis, amplifies fermentation efficiency. It achieves this by concurrently sustaining the integrity and optimal efficiency of the electron transport chain and optimizing metabolic fluxes, particularly those in the TCA cycle and oxidative phosphorylation. Consequently, it offers a promising strategy for mitigating carbon emissions and enhancing the production of biofuels and chemicals and thus holds immense potential for contributing to a more sustainable and environmentally friendly energy future.