Use of Enzymes in the Production of Semi-Synthetic Penicillins and Cephalosporins: Drawbacks and Perspectives

Abstract

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.

Microbial Enzymes: Tools for Biotechnological Processes

“…Enzymes are useful for preparing beta-lactam antibiotics such as semi-synthetic penicillins and cephalosporins [150]. Beta-lactams constitute 60%–65% of the total antibiotic market.…”

Hydrogen Peroxide in Biocatalysis. A Dangerous Liaison

“…The enzyme is inactivated by hydrogen peroxide, and the reaction product (an alpha-keto acid) is decarboxilated by this reagent. Considering that one of their main uses is the production of 7-cephalosporanic acid (7-ACA) from cephalosporin C, and that the second enzyme in the process (glutarayl acylase) recognizes glutaryl-7 ACA much better that alphaketo adiplyl-7ACA, this was a serious drawback in the design of the reaction [62]. In some cases, the excess hydrogen peroxide was destroyed in situ (most was consumed in the decarboxylation) by using catalase or some metal (e.g., manganese), or even both, immobilizing the enzyme on metal or metal oxide particles [159].…”

“…In other cases, this modification permits to obtain the target product as in the route to produce 7-aminocephalosporanic acid from cephalosporin C. D-amino acid oxidase produces Ketoadipyl-7-ACA, that after reacting with hydrogen peroxide produces glutaryl 7-ACA, which is the preferred substrate of the enzyme glutaryl acylase and has been the standard route to enzymatically produce 7-ACA until a cephalosporin acylase has been synthesized [61,62]. Even in this case, the presence of hydrogen peroxide becomes the bottleneck of the process and thus some routes avoiding this reagent have been proposed [62].…”

Ionization constants and solubility of compounds involved in enzymatic synthesis of aminopenicillins and aminocephalosporins

“…In the past several decades, the enzymatic synthesis of these antibiotics has been intensively studied as an option with lower environmental impact than traditional chemical synthesis [1,2]. Among the many strategies proposed for increasing the process effectiveness of aminopenicillin and aminocephalosporin enzymatic synthesis, use of the reagents at high concentrations is the most prevailing practice at last time [2][3][4][5][6][7][8][9].…”