Abstract: The potentiality of the conversion of 7-aminodeacetoxicephalosporanic acid(7-ADCA) to cephalexin using penicillin G acylase (PGA) (penicillin amidohydrolase, EC3.5.1.11) was studied in aqueous two-phase systems (ATPS).In a system consisting of 20%(mass) PEG 400 and 12%(mass) magnesium sulfate, the partition coefficient of PGA was less than 0.01, PGA almost completely partitioned into the magnesium sulfate-rich bottom phase. Meanwhile, the partition coefficient of cephalexin was 6.7, the partition coefficients of phenylglycine methyl ester (PGME) and 7-ADCA were 1.5 and 1.2, respectively. Then the stability of PGA in 20%(mass) PEG 400/15% (mass) magnesium sulfate ATPS was investigated and the results showed that PGA was suitable for the enzymatic synthesis of cephalexin in ATPS. When pure enzyme was used for bioconversion, a high yield of cephalexin (60%) was achieved form 75 mmol·L^-1 7-ADCA and 75 mmol·L^-1 PGME in the developed ATPS.

Key words:

双水相体系, 反应-萃取耦合, 分配系数, 头孢氨苄, 青霉素酰化酶

摘要： 应用聚乙二醇(PEG)/硫酸镁双水相体系(ATPS)进行了酶法合成头孢氨苄的反应-双水相萃取的耦合过程研究.通过考察头孢氨苄、苯甘氨酸甲酯和7-氨基脱乙酰氧基头孢烷酸(7-ADCA)在ATPS中的分配行为建立了一个含20％(质量)PEG 400和12％(质量)硫酸镁的ATPS，在此体系中头孢氨苄的分配系数为6.7，苯甘氨酸甲酯的分配系数为1.5，7-ADCA的分配系数为1.2，且青霉素酰化酶的分配系数小于0.01.底物、产物以及催化剂的分配特性有利于构建双水相体系应用于酶法合成头孢氨苄的反应-双水相萃取的耦合过程.对此双水相体系中青霉素酰化酶的稳定性研究表明催化剂亦适合此体系的构建.进而将此体系应用于头孢氨苄酶法合成，产率为60％左右，相对水相体系20％左右的产率取得了较好的结果.

关键词:

双水相体系, 反应-萃取耦合, 分配系数, 头孢氨苄, 青霉素酰化酶