Successful bi-enzyme stabilization for the biomimetic cascade transformation of carbon dioxide

In nature, carbon dioxide (CO₂) conversion to valuable chemicals occurs via several metabolic pathways through multi-enzymatic reactions. Here, we aimed to mimic this by introducing enzyme immobilization in microbead compartments forming a stabilized multi-enzyme system. The system is assembled by encapsulation of phosphoenolpyruvate carboxylase (PEPCase) in branched polymeric microbeads followed by carbonic anhydrase (CA) immobilization on the silica-shell surface of the microbeads. The step-by-step construction of the CA/PEPCase microbeads is monitored based on the stability of each enzyme and cascade enzymatic oxaloacetate (OAA) production rate from a CO₂ substrate. Each CA and PEPCase in the microbeads preserved their catalytic activity even after 20 times of reuse, with facile magnetic separability at room temperature. The CA/PEPCase system retained about 75% of the OAA production rate of free CA/PEPCase by forming a multi-enzyme/microbead complex structure. To the best of our knowledge, this report is the first demonstration of a stabilized cascade CA/PEPCase system that mimics the biomimetic CO₂ conversion by a multi-enzymatic pathway found in biological systems.