Improving Selectivity and Productivity of the Enzymatic Synthesis of Ampicillin with Immobilized Penicillin G Acylase

An experimental design was applied to improve the reaction conditions for enzymatic synthesis of ampicillin from phenylglycine methyl ester (PGME) and 6-aminopenicillanic acid (6-APA), catalyzed by penicillin G acylase from E. coli immobilized on an agarose-glyoxyl derivative. The presence and magnitude of interactions between reaction variables were estimated using a 2 factorial design. A batch reactor was employed to assess the influence of the following variables: pH, temperature, initial 6-APA concentration, buffer concentration, and the presence of methanol. Response variables were productivity, selectivity, and yield (based on initial 6-APA concentration). The best synthesis yield (56.9%) was at T = 4oC and pH 6.5. The highest productivity (49.3 × 10mM of antibiotic/min) was achieved at T = 25oC and pH 6.5. Our results indicate that it is possible to achieve high productivity for this system while maintaining a high selectivity and yield.