Nonconventional Reactor for Enzymatic Synthesis of Semi-Synthetic β-Lactam Antibiotics

Selectivity and kinetic modeling of penicillin G acylase variants for the synthesis of cephalexin under a broad range of substrate concentrations

The kinetics of cephalexin synthesis and hydrolysis of the activated acyl-donor precursor phenylglycine methyl ester (PGME) were characterized under a broad range of substrate concentrations. A previously developed model by Youshko-Svedas involving the formation of the acyl-enzyme complex followed by binding of the nucleophilic β-lactam donor does not fully estimate the maximum reaction yields for cephalexin synthesis at different concentrations using initial-rate data. 7-aminodesacetoxycephalosporanic acid (7-ADCA) was discovered to be a potent inhibitor of cephalexin hydrolysis, which may account for the deviation from model predictions. Three kinetic models were compared for cephalexin synthesis, with the model incorporating competitive inhibition due to 7-ADCA yielding the best fit. Additionally, the βF24A variant and Assemblase® did not exhibit significantly different kinetics for the synthesis of cephalexin compared to the wild-type, for the concentration range evaluated and for both initial-rate experiments and time-course synthesis experiments. Lastly, a continuous stirred-tank reactor for cephalexin synthesis was simulated using the model incorporating competitive inhibition by 7-ADCA, with clear tradeoffs observed between productivity, fractional yield, and PGME conversion.

Reactive crystallization: a review

Reactive crystallization is not new, but there has been recent growth in its use as a means of improving performance and sustainability of industrial processes.

Penicillin acylase-catalyzed synthesis of N-bromoacetyl-7-aminocephalosporanic acid, the key intermediate for the production of cefathiamidine

BACKGROUND

Enzymatic approaches have become promising alternatives to chemical methods for the production of semi-synthetic β-lactam antibiotics. In this work, enzymatic synthesis of N-bromoacetyl-7-aminocephalosporanic acid (N-bromoacetyl-7-ACA), the key intermediate for the production of cefathiamidine, was reported for the first time.

RESULTS

Of the immobilized penicillin acylases (PAs) tested, PGA-750 was the best biocatalyst. Optimization of the biocatalytic process was conducted. The optimal acyl donor, molar ratio of acyl donor to 7-ACA, pH, temperature, 7-ACA concentration, and enzyme dosage were methyl bromoacetate, 3, 7.5, 20 °C, 50 mmol/L and 4 U/mL, respectively. Under the optimal conditions, enzymatic N-acylation of 7-ACA with methyl bromoacetate afforded the desired product with the yield of 85% in 2 h, where the synthesis/hydrolysis (S/H) ratio was approximately 1.5. The immobilized enzyme PGA-750 exhibited good operational stability, and the relative yields of approximately 90% and 63% were achieved, respectively, when it was reused in 7th and 11th batch.

CONCLUSIONS

An enzymatic approach to N-bromoacetyl-7-ACA, the key intermediate for the industrial production of cefathiamidine, has been developed successfully in a fully aqueous medium. The present work may open up a novel opportunity for the production of cefathiamidine through a simple and green process.Graphical abstractEnzymatic synthesis of N-bromoacetyl-7-ACA, the key intermediate for the production of cefathiamidine, was reported for the first time.

Reactive crystallization of β-lactam antibiotics: strategies to enhance productivity and purity of ampicillin

Crystallization of ampicillin, as it is synthesized, enhances the yield by reducing hydrolysis.