Evaluation of different enzymes as catalysts for the production of beta-lactam antibiotics following a kinetically controlled strategy

Several beta-lactam acylases produced by different microorganisms (Escheric hia coli, Kluyvera citrophila, Acetobacter turbidans, and Bacillus megateri um) have been evaluated as catalysts for the syntheses of relevant beta-lac tam antibiotics (ampicillin, cephalexin, and cefamandole). These enzymes di splayed very different synthetic properties showing large differences in sy nthetic yields (by a 4- to 5-fold factor) depending on the antibiotic and t he enzyme. The enzyme from A. turbidans presented the best properties for t he synthesis of ampicillin, which is a low activity in the hydrolysis of th e antibiotic and a high specificity for the transformation of the ester int o antibiotic. Although this enzyme was able to transform approximately 80% of phenylglycine methyl ester into ampicillin, it was unsuitable for the sy nthesis of cephalexin and cefamandole. In fact, all of the enzymes showed s ignificant hydrolysis rates of the antibiotics compared to the synthetic ac tivity, although the enzyme from E. coli exhibited the highest specificity for the transformation of eaters into these antibiotics. To prevent the hyd rolysis of the antibiotic, a two-phase aqueous system was used to extract t he antibiotic from the enzyme environment. In this way, high synthetic yiel ds could be obtained, e.g. 80% of phenylglycine methyl ester was transforme d into cephalexin using the enzyme from E. coli. (C) 1999 Elsevier Science Inc. All rights reserved.