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KMID : 0545120010110020329
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Journal of Microbiology and Biotechnology
2001 Volume.11 No. 2 p.329 ~ p.332
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pH-Controlled Synthesis of Cephalexin by a Purified Acetobacter turbidans Ampicillin Acylase
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NAM, DOO HYUN
RYU, YEON WOO/DEWEY D. Y. RYU
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Abstract
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It has been known that, in enzymatic synthesis of cephalexin, the conversion yield was reduced by high loading of ampicillin acylase. In order to elucidate this phenomena, pH-controlled synthesis of cephalexin was examined using a purified Acetobacter turbidans acylase. When the pH of the reaction mixture was maintained at 6.20±0.04, the reduction of the maximal conversion rate was not observed even with high enzyme loading. The kinetic parameters also suggest that pH drop during the enzymatic synthesis of cephalexin was mainly attributed to the rapid hydrolysis of D-α-phenylglycine methyl ester to D-α-phenylglycine, rather than the disappearance of 7-amino-3-deacetoxycephalosporanic acid for cephalexin synthesis. At higher molar ratio of two substrates, [D-α-phenylglycine methyl esterl/[7-amino-3-deacetoxycephalosporanic acid], the conversion rate was also elevated under pH-controlled enzymatic synthesis, which implies that the main reason for the pH drop is due to the production of D-α-phenylglycine. In order to reduce the hydrolysis of D-α-phenylglycine methyl ester, the effect of a water-methanol cosolvent system on the conversion profile was also examined. Even though the conversion rate was increased in 10% methanol solution, a higher than 16% methanol in the reaction mixture caused an inactivation of enzyme.
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