Green and Efficient Conversion of CO₂ to Methanol by Biomimetic Coimmobilization of Three Dehydrogenases in Protamine-Templated Titania

A green and efficient mutienzyme system was established, which efficiently converted carbon dioxide into methanol, by encapsulating three dehydrogenases within titania particles through a facile and mild biomimetic mineralization process. The enzyme-containing titania particles were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The results indicated that the enzyme-containing titania particles were amorphous and consisted of interconnected nanospheres with sizes in the range of 400−600 nm. The three encapsulated dehydrogenases (formate dehydrogenase, formaldehyde dehydrogenase, alcohol dehydrogenase) sequentially converted carbon dioxide into HCOOH, CHOH, and CH 3 OH using NADH as a terminal electron donor for each dehydrogenase-catalyzed reduction. Compared to the open-style system which directly performed the bioconversion using free enzymes in aqueous solution, higher reaction yield in a wider pH and temperature range was obtained by the closed-style coimmobilization multienzyme system.