Composite Enzyme/CaCO₃@Hydrogel Particles for Continuous Cascade Multienzymatic Catalysis

Immobilization of multiple enzymes in particles creates opportunities to organize a complex network of biochemical reactions for continuous cascade catalysis. In this work, hydrogel particles integrated with enzyme/CaCO3 nanoparticles are created via droplet-template synthesis for the continuous cascade catalysis of CO2 into methanol. Three enzymes, including formate dehydrogenase (FateDH), formaldehyde dehydrogenase (FaldDH), and alcohol dehydrogenase (ADH), are separately immobilized in these CaCO3 nanoparticles inside the hydrogel particles. The obtained FateDH/CaCO3@PEGDA, FaldDH/CaCO3@PEGDA, and ADH/CaCO3@PEGDA hydrogel particles enable good performance for cascade enzymatic catalysis in batch, showing a higher conversion rate than the free enzymes and the hydrogel particles coencapsulated with the three enzymes. Meanwhile, these enzyme/CaCO3@PEGDA hydrogel particles exhibit good repeatability for the cascade enzymatic catalysis, typically showing a ∼12% decrease in conversion rate after 7 cycles. Moreover, these enzyme/CaCO3@PEGDA hydrogel particles are filled in a U-shaped reactor for continuous cascade enzymatic catalysis. When three units of such reactors are sequentially used, these enzyme/CaCO3@PEGDA hydrogel particles allow efficient conversion of CO2 dissolved in solution into methanol, exhibiting a maximum methanol yield at 6.00 mM. This work provides a simple, environmentally friendly, and low-cost strategy for creating multienzyme-immobilized particles for cascade enzymatic catalysis.