Abstract:

Biosynthesis of chiral epichlorohydrin (ECH) from 1,3-dichloro-2-propanol (1,3-DCP) catalyzed by halohydrin dehalogenases is an efficient and green synthetic route which exhibits advantages of mild reaction conditions, high atomic economy and environmental friendliness. Therefore, it has broad application prospects. Since the substrate and product in this route is easily to be degraded in aqueous phase, a two-phase system of water and organic solvents was applied. In order to improve the stability of the enzyme in organic solvents, a Pickering emulsion system was constructed with modified SiO₂ as emulsifier for the enzyme-medicated biocatalysis of chiral ECH, and its catalytic performance was characterized. The results showed that the stability of the Pickering emulsion-based halohydrin dehalogenase in the water-organic solvent two-phase system was significantly improved, and its half-life was increased from 9.7 h to 20.1 h. After that, the reaction conditions were optimized and 50 mmol/L 1,3-DCP was effectively converted within 40 min. The yield of product (S)-ECH reached 93.6% with e.e. value of 95.3%. The obtained results laid the foundation for highly efficient biocatalytic synthesis of chiral ECH.

Key words: biocatalysis, Pickering emulsion, enzyme, system optimization, chiral epichlorohydrin

摘要：

卤醇脱卤酶催化1,3-二氯-2-丙醇（1,3-DCP）合成手性环氧氯丙烷（ECH）具有反应条件温和、原子经济性高、环境友好等优势，应用前景广阔。由于该路线中底物与产物在水相中稳定性差、易分解，因此构建了水与有机溶剂两相反应体系。为了提高酶在有机溶剂中的稳定性，建立了以改性SiO₂颗粒为固体乳化剂的Pickering乳液酶催化体系并对其催化性能进行表征。结果表明，基于Pickering乳液的卤醇脱卤酶在水-有机溶剂两相体系中的稳定性显著提高，其半衰期从9.7 h提高至20.1 h。进一步优化了反应条件，以50 mmol/L 1,3-DCP为底物，反应40 min (S)-ECH产率达93.6%，目标产物光学纯度（e.e.值）为95.3%，为高效生物催化合成手性ECH奠定了基础。

关键词: 生物催化, Pickering乳液, 酶, 体系优化, 手性环氧氯丙烷