生物拆分法制备D-天冬氨酸

目的]利用L-天冬氨酸-β-脱羧酶生物转化拆分DL-天冬氨酸得到D-天冬氨酸的工艺过程。方法]研究了碳源、有机氮源、转化过程pH值和转化温度对发酵液L-天冬氨酸-β-脱羧酶酶活力的影响,探讨了L-天冬氨酸-β-脱羧酶的热稳定性及L-丙氨酸对L-天冬氨酸-β-脱羧酶热稳定性的影响,并测定了拆分产物的主要指标。结果]糖类对该酶的生物合成有明显的阻遏作用,而富马酸和苹果酸是很好的碳源物质。有机氮源中蛋白胨浓度对发酵液酶活力的影响较大,当牛肉膏浓度为0.2%,玉米浆为1.0%,蛋白胨为1.0%时发酵液酶活力可以达到最高。转化过程最适pH值为6～7。转化过程最适温度50℃。温度超过60℃酶失活比较严重。浓度6.0%以上的丙氨酸能显著提高转化过程中酶的热稳定性。结论]利用D-天冬氨酸和L-丙氨酸的等电点的差异来分离提取D-天冬氨酸的制备工艺,其工艺简单,原料价格适宜,提取方便,工艺路线要比其他方法更便捷,更容易产业化。

Production of D-Aspartic Acid by Biotransformation

Objective] The research aimed to investigate the process of production of D-aspartic acid from DL-aspartic acid with L-aspartate-β-decarboxylase by biotransformation.Method] The effects of carbon source,organic nitrogen source,pH value during transformation and transition temperature on activity of L-aspartate-β-decarboxylase were studied,the thermal stability of L-aspartate-β-decarboxylase and the effects of L-alanine on its thermal stability were discussed,and the main indices of separation products were determined.Result] From experiments,it may be concluded that some sugars played a negative role in formation of decarboxylase and some organic acids especially fumaric and malic acid were proper carbon source for formation of that.The concentration of peptone notably effected the concentration of decarboxylase.Through the orthogonal test,the optimum concentration of beef extract,corn steep and peptone was 0.2%,1.0% and 1.0%.From test,under pH value 6-7 and temperature 50 ℃,the biotransformation process might get desired results.When temperature beyond 60 ℃,the inactivation of decarboxylase should be considerable.If the concentration of L-alanine exceeded 6.0%,the activation of decarboxylase would be mostly protected against high temperature.Conclusion] This process of production of D-aspartic acid from DL-aspartic acid with L-aspartate-β-decarboxylase by biotransformation was simple and convenience,and its material price was suitable.The technics way was more convenient and easier to be industrialized.