Immobilization of alcohol dehydrogenase on ceramic silicon carbide membranes for enzymatic CH3OH production

BACKGROUNDAlcohol dehydrogenase (ADH; EC 1.1.1.1) catalyzes oxidation of CH3OH to CHOH during NAD(+) reduction to NADH. ADH can also accelerate the reverse reaction, which is studied as part of cascadic enzymatic conversion of CO2 to CH3OH. In the present study, immobilization of ADH onto macroporous membranes of silicon carbide (SiC) was investigated for CHOH to CH3OH conversion. RESULTSImmobilization techniques included physical adsorption directly to the membrane and functionalization of the membrane with polyethylenimine (PEI) or (3-aminopropyl)triethoxysilane (APTES) followed by glutaraldehyde (GA) cross-linking. Enzyme loadings, flux, NADH conversion, and overall ADH reusability were assessed. Enzyme loadings were similar, but substrate conversion was approximately 2 and 2.5 times higher for APTES-GA and PEI-GA, respectively, and the relative activity retention was better than for physical adsorption. Membrane surface treatment with NaOH prior to APTES-GA immobilization resulted in significant improvement in enzyme loading and a doubling of ADH activity as well as higher activity during recycling as the ADH destabilization rate was unaffected. CONCLUSIONSThe results provided proof-of-concept for the use of NaOH-treated SiC membranes for covalent enzyme immobilization and biocatalytic efficiency improvement of ADH during multiple reaction cycles. These data have implications for the development of robust extended enzymatic reactions. (c) 2018 Society of Chemical Industry