化学-酶法制备L-高苯丙氨酸

以苯丙酸乙酯为原料，通过正交设计优化2-氧4-苯基丁酸盐的制备条件：苯丙酸乙酯与草酸二乙酯摩尔比为1：3，缩合反应时间为2．5h，H2SO4质量分数为20％，水解反应时间为15h，优化条件下2-氧-4-苯基丁酸盐的产率为68．24％。随后，利用E．coli A5所产的天冬氨酸转氨酶为生物催化剂制备L-高笨丙氨酸。酶转化反应的最适条件为：游离细胞体系pH、温度、底物质量浓度和细胞质量浓度分别为8．5、37℃、20g/L和30g／L；而固定化细胞体系则分别为7．0—9．0、40℃、10g／L和30g/L。采用廉价的L-谷氨酸（L—Glu）作为氨基供体，添加表面活性剂有利于提高L-HPA产率。通过研究固定化细胞转化反应进程，结果发现8h内90％的底物可转化为L—HPA。

Process for producing of L-homeoephenylalanine by chemo-enzymatic method

The 2-oxo-4-phenylbutanate （OPBA） was prepared from ethyl 3-phenylpropionate firstly, and orthogonal experimental design was used to optimize the reaction conditions as follows ： molar ratio of ethyl 3-phenylpropionate to diethyl oxalate was 1 ： 3, condensation reaction time was 2.5 h, concentration of H2SO4 was 20%, hydrolysis reaction time was 15 h, and the yield of L-HPA was 68.24% under the optimized conditions. Secondly, L-HPA was prepared from 2-oxo-4-phenylbutanate catalyzed by aspartate aminotransferase produced from E. coli A5, and the optimum conditions were given ： pH, temperature, concentration of OPBA, and cell content was 8.5, 37 ℃, 20 g/L, and 30 g/L, respectively for the free cells system, and 7.0 - 9.0, 40℃ , 10 g/L, and 30 g/L in the immobilized cells system. The amino donor was L-Glu, and the surfactants had a direct influence on the yield of L-HPA. In the reaction catalyzed by the immobilized cells, 90% of the substrate can be converted as L-HPA in 8 h.