Amidase-Catalyzed Desorption of CO₂ Captured in Aqueous Monoethanolamine (MEA) Solutions

Aqueous monoethanolamine (MEA) solutions can absorb CO₂ from industrial point sources via amine scrubbing. Mechanistically, CO₂ diffuses in and reacts with MEA or hydroxide to form a mixture of carbamate and carbonate/bicarbonate. Subsequently, CO₂ is released for storage or utilization via an energy-intensive thermal solvent-regeneration process. Here, we explored biocatalytic acceleration of the solvent regeneration step, which accounts for the dominant energy cost of carbon dioxide removal (CDR) processes. We conducted a sequence mining campaign based on urethane-degrading Amidase Signature superfamily enzymes and discovered amidases that hydrolyze MEA carbamate, thereby increasing the overall release rate of CO₂. The most promising candidate, an amidase from Parageobacillus caldoxylosilyticus (PcAmd), showed good thermostability (T_m around 70°C) and a specific activity against MEA carbamate of about 1 U/mg (20 nKat/mg). We found that PcAmd accelerated the regeneration of MEA sorbent. Specifically, PcAmd at 1 µM increased the initial CO₂ release rate by about 20%, and the time required to release 80% of the captured CO₂ was reduced by approximately half compared to enzyme-free solutions. These results identified a novel potential of amidases in carbon capture and motivated further efforts to discover or engineer enzymes with better stability and activity for industrial CDR applications.