重庆大学王丹团队：多酶级联耦合电化学实现从CO2高效合成L-乳酸

Core Viewpoint - The article discusses a novel multi-enzyme cascade-electrochemical coupling system developed by Professor Wang Dan's team at Chongqing University, which efficiently synthesizes L-lactic acid from ethanol and CO₂, presenting a new strategy for CO₂ resource utilization and green chemical synthesis [2][20]. Summary by Sections Multi-Enzyme Cascade System - A multi-enzyme cascade system was constructed that does not rely on external NADH, utilizing ADH, PDC, and LDH to convert ethanol to acetaldehyde and CO₂ to pyruvate, ultimately producing L-lactic acid [4]. - PDC was identified as the rate-limiting enzyme, with a high-activity mutant Ptdqy developed through random mutation, resulting in a Kcat/Km value 2.92 times higher than the wild type, leading to a 2.94-fold increase in L-lactic acid production [4][10]. Electrochemical Platform - An electrochemical platform was established to regenerate NADH efficiently at -1.5 V and 0.2 mM NAD⁺, achieving an 18% increase in yield compared to pure enzyme systems, thus addressing the coenzyme regeneration challenge [4][16]. Ionic Liquids - The ionic liquid [CH][His] was selected as a solvent, demonstrating a CO₂ adsorption capacity of 0.57 mol/mol, which enhanced L-lactic acid production by 1.89 times compared to Tris buffer systems, making it the optimal solvent choice [4][19]. Scale-Up Production - The system successfully scaled up to synthesize 22.5 mM (2.03 g/L) of L-lactic acid using 50 mM ethanol as a substrate, with production costs 10% lower than traditional microbial fermentation routes and an atomic utilization rate of 100% [4][22]. Industrial Application Potential - This system not only achieves green production with 100% atomic utilization but also reduces L-lactic acid synthesis costs through scale-up validation and cost control, making it a potential alternative to traditional fermentation routes in food, chemical, and biodegradable materials industries [22]. Future Optimization Directions - Future efforts will focus on reducing the cost of NAD⁺, which currently constitutes a significant portion of production costs, and exploring the application of this coupling platform for synthesizing other high-value chemicals from CO₂ [23]. Concept Learning - L-lactic acid is a key raw material in food, chemical, and material sectors, and this research provides a new pathway for its green production by utilizing CO₂ and ethanol, thus avoiding competition with food resources [24]. - Multi-enzyme cascade reactions allow for high substrate flexibility and efficiency, with the rate-limiting enzyme's activity directly influencing overall reaction rates and yields [25]. - The electrochemical coupling method for NADH regeneration offers a low-cost solution for continuous coenzyme supply, enhancing production efficiency [26]. - Ionic liquids enhance CO₂ solubility and enzyme stability, contributing significantly to the increased yield of L-lactic acid [27].