Strained Partnership: Biocompatibility and Transcriptomic Responses of Hydrogenotrophic Methanogens to Methyl Diethanolamine in Bio-integrated Carbon Capture and Utilization.

Biointegrated carbon capture and utilization (BICCU) represents a promising alternative to conventional carbon capture technologies, combining microbial methanogenesis with CO2 capture agents, such as methyl diethanolamine (MDEA), to produce renewable methane from dilute CO2 sources. However, the biotoxicity of these solvents poses a major challenge to the viability of the BICCU approach. This study investigates the biocompatibility and physiological responses ofMethanococcus maripaludis and Methanosarcina barkeri to MDEA, through batch experiments and transcriptomic analysis. Both methanogens exhibited inhibited methane production when exposed to MDEA, with M. barkeri displaying higher sensitivity. M. maripaludis maintained the highest CH4 production rate at 30 mmol/L MDEA, while M. barkeri was almost fully inhibited at this concentration. Transcriptomic analysis revealed upregulation of genes associated with S-layer formation, cell envelope biogenesis, glycosyltransferase activity, and ion transport, alongside downregulation of lysine biosynthesis and secretion system genes. These findings suggest a metabolic trade-off, where cellular energy is reallocated toward stress response mechanisms. Results demonstrate that, while MDEA can be integrated with microorganisms, the exact response will depend on the methanogenic strain. Future research should focus on more biocompatible solvents and the selection of resilient methanogenic strains.