Use of enzymes in the production of semi-synthetic penicillins and cephalosporins: drawbacks and perspectives.

Semi-synthetic β-lactamic antibiotics are the most used anti-bacteria agents, produced in hundreds tons/year scale. It may be assumed that this situation will even increase during the next years, with new β-lactamic antibiotics under development. They are usually produced by the hydrolysis of natural antibiotics (penicillin G or cephalosporin C) and the further amidation of natural or modified antibiotic nuclei with different carboxylic acyl donor chains. Due to the contaminant reagents used in conventional chemical route, as well as the high energetic consumption, biocatalytic approaches have been studied for both steps in the production of these very interesting medicaments during the last decades. Recent successes in some of these methodologies may produce some significant advances in the antibiotics industry. In fact, the hydrolysis of penicillin G to produce 6-APA catalyzed by penicillin G acylase is one of the most successful historical examples of the enzymatic biocatalysis, and much effort has been devoted to find enzymatic routes to hydrolyze cephalosporin C. Initially this could be accomplished in a quite complex system, using a two enzyme system (D-amino acid oxidase plus glutaryl acylase), but very recently an efficient cephalosporin acylase has been designed by genetic tools. Other strategies, including metabolic engineering to produce other antibiotic nuclei, have been also reported. Regarding the amidation step, much effort has been devoted to the improvement of penicillin acylases for these reactions since 1960. New reaction strategies, continuous product extraction or new penicillin acylases with better properties have proven to be the key to have competitive biocatalytic processes. In this review, a critical discussion of these very interesting advances in the application of enzymes for the industrial synthesis of semi-synthetic antibiotics will be presented.