过氧化氢对D-氨基酸氧化酶转化头孢菌素C为戊二酰-7-氨基头孢烯酸反应的影响

Effect of Hydrogen Peroxide on the Conversion of Cephalosporin C to Glutaryl-7-ACA by D-Amino Acid Oxidase

在D-氨基酸氧化酶D1AAO转化头孢菌素C(CPC)为戊二酰基-7-氨基头孢烯酸(Gl-7-ACA)的反应中,所生成的过氧化氢同时与CPC和Gl-7-ACA发生的氧化副反应是造成目标产物收率损失的关键因素之一。通过联用溶氧电极和过氧化氢电极,测定了DAAO转化CPC为Gl-7-ACA的反应体系内溶氧浓度与相应的过氧化氢浓度的变化曲线,测知反应体系中过氧化氢浓度积累最高可达5mmol·L-1。模拟该反应条件下过氧化氢的氧化反应可知,在过氧化氢浓度较低时,溶液的酸性可加速该氧化反应。在中性条件下,过氧化氢浓度为5mmol·L-1时,反应1h后,CPC的氧化损失为2%,Gl-7-ACA的氧化损失为3%。通过改进氧气分布器、搅拌转速和并调控氧气流量以控制溶液中溶解氧的浓度,来适度地降低物系中过氧化氢积累浓度,使反应收率提高了2.2%。

The simultaneous oxidation of cephalosporin C （CPC） and glutaryl-7-aminocephalosporanic acid （G1-7-ACA） by the hydrogen peroxide, which is formed as a transient product during the conversion reaction, is one of the key factors that result in the loss of the yield in the enzymatic conversion of CPC to G1-7-ACA by D-amino acid oxidase （DAAO）. The curves of the concentration of the dissolved oxygen vs. the corresponding concentration of the hydrogen peroxide in the solution were measured by the dissolved oxygen probe and the hydrogen peroxide probe. It was detected that the hydrogen peroxide can accumulate up to 5mmol·L^-1 in the solution. It was found that the acidity of the solution can accelerate the oxidation in low hydrogen peroxide concentration by means of simulating the oxidation of the hydrogen peroxide under the same conditions. While the concentration of the hydrogen peroxide is 5 mmol·L^-1, the loss of CPC is 2% and G1-7-ACA 3% in one hour under neutrality condition. The yield can be improved by about 2.2% by enhancing the oxygen distributor, regulating the speed of the stirrer and adjusting the flow rate of the oxygen in order to reasonably reduce the accumulation of the hydrogen peroxide in the solution.