有机相酶法不对称水解乳酸乙酯

探讨了在有机介质中酶催化外消旋乳酸乙酯不对称水解制备L-乳酸的可行性。 研究了反应介质、不同来源的酶、摇床转速、水含量、乳酸乙酯浓度及温度等因素对反应的影响。结果表明，N435的活性和选择性较高，叔丁醇和异辛烷的混合溶剂（体积比为1∶1）为最合适的反应介质，其余最适条件为：摇床转数200 r•min^-1、水含量（水与底物的质量比）1∶5、乳酸乙酯浓度0.27 g•ml^-1、酶浓0.8 g•mol^-1、反应温度60℃，在此条件下反应16 h得产物ee值为90.02% ，产率为28.69%。 最后研究了乳酸乙酯不对称水解的动力学，结果表明反应符合米氏方程，属于双底物抑制的双乒乓机制，并考察了D-乳酸乙酯和D-乳酸在建立反应动力学模型时的影响。

Lipase-catalyzed enantioselective hydrolysis of ethyl lactate in organic solvents

The feasibility of preparing L-lactic acid by lipase-catalyzed enantioselective hydrolysis of ethyl lactate in organic solvents was explored.The effects of enzyme sources and organic media on the reaction were examined respectively.The results showed that Candida antarctic lipase B（N435）had both the highest catalytic activity and enantioselectivity.The mixture of tert-butanol and isooctane (1∶1,vol) was the most suitable media for the reaction, and other optimum conditions for catalysis were 200 r•min^-1 for shaking rate, 1∶5 for mass ratio of ethyl lactate to water, 0.27 g•ml^-1 for ethyl lactate concentration, 0.8 g•mol^-1 for enzyme concentration and 60℃ for reaction temperature, respectively.Under these optimal conditions, a product enantiomeric excess (ee) of 90.02% and the yield of 28.69% were achieved after 16 h reaction time.The kinetics of lipase-catalyzed enantioselective hydrolysis of ethyl lactate was investigated too.The experimental results indicated that: the reaction could be described in terms of the Michaelis-Menten equation with a Ping-Pong Bi-Bi mechanism and competitive inhibition by both substrates.The effects of D-lactic acid and D-ethyl lactate substrate concentrations on the initial rate of asymmetric hydrolysis were studied.