Bioinspired Approach to Multienzyme Cascade System Construction for Efficient Carbon Dioxide Reduction

An efficient multienzyme cascade system based on ultrathin, hybrid microcapsules was constructed for converting CO2 to methanol by combining the unique functions of catechol and gelatin. Gelatin was modified with catechol groups (GelC) via well-defined EDC/NHS chemistry, thus endowed with the ability to covalently attach enzyme molecules. Next, the first enzyme (FateDH)-containing CaCO3 templates were synthesized via coprecipitation and coated with a GelC layer. Afterward, GelC was covalently attached with the second enzyme (FaldDH) via Michael addition and Schiff base reactions. Then, GelC induced the hydrolysis and condensation of silicate, and the third enzyme (YADH) was entrapped accompanying the formation of silica particles. After removal of CaCO3 templates, the GelCSi-based multienzyme system was obtained, in which the three enzymes were appropriately positioned in different places of the GelCSi microcapsules, and the amount of individual enzyme was regulated according to enzyme activity. The system exhibited high activity and stability for converting CO2 into methanol. In detail, the system displayed much higher methanol yield and selectivity (71.6%, 86.7%) than that of multienzyme in free form (35.5%, 47.3%). The methanol yield remained 52.6% after nine times of recycling. This study will provide some guidance on constructing diverse scaffolds for applications in catalysis, drug and gene delivery, and biosensors.