Three-liquid-phase system: A highly efficient, enantioselective, and enzyme-recoverable platform for enzymatic chiral resolution reaction

Enzymatic resolution of chiral secondary alcohols has attracted wide attention due to its low cost and environmental pollution as well as mild environmental requirements. However, in the traditional enzymatic reaction system, its application is greatly limited by the low enzymatic catalytic efficiency and enantioselectivity, as well as difficulty in reusing enzymes. Therefore, it is urgent to develop novel enzymatic chiral resolution systems that can overcome these drawbacks. The study assessed the use of a three-liquid-phase system (TLPS) as a novel enzymatic reaction and separation system for the enzymatic chiral resolution of racemic 1-(4-methoxyphenyl) ethanol acetate. Among the systems tested, polymer/salt TLPSs presented promising potential for practical use with superior catalytic efficiency, 10-fold increase in enantiomeric ratio, and 36 % enhancement in hydrolysis efficiency, especially for PEG600/Na 2 SO 4 TLPS in comparison with the O/W system. The partition coefficient of the product between the substrate-enriched and product-enriched phases also decreased by more than half for the PEG600/Na 2 SO 4 TPLS when compared with the O/W system, and this ensured improved separation of the products from the substrate. Droplet size distribution and microstructure analysis further indicated that the TLPS provided a new phase-transfer catalytic interface with large interfacial reaction area, which was a plausible reason for the enhanced catalytic efficiency. Furthermore, the enzymes that are highly enriched in the middle phase could also be reused, at least for eight rounds without significant loss in enantioselectivity and catalytic efficiency. The high reusability of the enzyme, in addition to promising applicability to different reaction systems were also demonstrated, suggesting the potential application of the TLPS for effective interfacial selective enzymatic catalysis.