金黄节杆菌CYC705腈水解酶催化亚氨基二乙酸的合成

Synthesis of Iminodiacetic Acid Catalyzed by a Nitrilase from Arthrobacter aurescens CYC705

将金黄节杆菌CYC705（Arthrobacter aurescens CYC705）腈水解酶用于生物催化合成亚氨基二乙酸（IDA）,从生物催化剂的形式、生物催化反应过程优化和反应体系放大3个方面进行了考察。在氨基载体固定化酶、环氧基载体固定化酶、海藻酸钠固定化细胞、壳聚糖固定化细胞和游离全细胞几种生物催化剂形式中,壳聚糖固定化细胞催化效率最高、稳定性最好。通过反应体系、反应温度、金属离子、底物浓度、固定化细胞投量等因素的优化,确定了最佳的生物催化反应条件：以50 mmol/L p H=6.6磷酸氢二钠-柠檬酸缓冲液作为反应体系,底物亚氨基二乙腈（IDAN）的浓度为200 mmol/L,添加Co Cl2至终浓度为1 mmol/L,反应温度37℃,固定化细胞投量为0.25 g每5 m L反应体积。在该条件下,反应2 h可将IDAN完全转化为IDA。进一步将反应体系放大10倍,催化200 mmol/L的IDAN完全转化为IDA仅需1 h。

A nitrilase from Arthrobacter aurescens CYC705 was used to synthesize iminodiacetic acid（IDA）. The biocatalyst form, optimization of biocatalysis process and scale-up of the reaction system were investigated in detail. Several biocatalyst forms including aminated carrier immobilized nitrilase, epoxy carrier immobilized nitrilase, sodium alginate immobilized cells, chitosan immobilized cells and free whole cells were prepared and compared. It was found that the chitosan immobilized cells had the highest catalytic efficiency and the best stability. After optimizing reaction system, reaction temperature, metal ion concentration, substrate concentration and additive amount of chitosan immobilized cells, the optimal reaction conditions were obtained as follows： 50 mmol/L p H 6.6 Na2 HPO4-citric acid buffer as reaction medium, iminodiacetonitrile（IDAN） concentration 200 mmol/L, final Co Cl2 concentration in the reaction medium 1 mmol/L, reaction temperature 37 ℃, addition amount of chitosan immobilized cells 0.25 g/5 m L reaction volume. Under these conditions, IDAN could be completely hydrolyzed to IDA within 2 h. However, when the reaction system was amplified 10-fold, the time required to catalyze the full conversion of 200 mmol/L IDAN to IDA was only 1 h.