Enzymatic Synthesis of Amoxicillin by the Cell-Bound α-Amino Acid Ester Hydrolase of Xanthomonas citri

Whole cells of Xanthomonas citri K24, a penicillinase-deficient α-amino acid ester hydrolase producer, were effectively used for synthesis of amoxicillin from d-α-(p-hydroxyphenyl)-glycine methyl ester (HPGME) and 6-aminopenicillanic acid (6-APA). The yield of amoxicillin from 6-APA was increased by reducing the ionic strength of the reaction mixture and by adding 2-butanol to the reaction mixture. Increasing the HPGME/6-APA ratio above 1:1 raised the yield of amoxicillin. The optimum pH for the synthetic reaction was between 6 and 7, and the optimum temperature, 20°C. The addition of 2-butanol repressed the enzymatic hydrolysis of HPGME, and enhanced the acylation of 6-APA. More than 90% of the added 6-APA was converted into amoxicillin under the optimum conditions.