Single-step conversion of cephalosporin-C to 7-Aminocephalosporanic acid by free and immobilized cells of Pseudomonas diminuta

Potential of Biocatalysis in Pharmaceuticals

Biocatalysis has been continuously evolving as an essential tool which is playing a significant role in the industrial synthesis of chemicals, active pharmaceuticals, pharmaceutical intermediates, etc. where the high-yielding chemo-, regio-, and enantioselective reactions are needed. Despite its vital importance, industrial biocatalysis is facing certain limitations such as operational stability, economic viability, efficient recovery, and reusability. The limitations mentioned can be overcome by the isolation of specific enzyme producers from extreme environment by protein engineering, bioinformatics, and recombinant DNA technologies. Recently, chemoenzymatic pathway and biological cascade reactions have also been developed and designed to perform the synthesis of pharmaceuticals. In this chapter, we compile the broad applications of biocatalysts in the synthesis of pharmaceuticals.

Three steps in one pot: biosynthesis of 4-hydroxycinnamyl alcohols using immobilized whole cells of two genetically engineered Escherichia coli strains

Background

4-Hydroxycinnamyl alcohols are a class of natural plant secondary metabolites that include p-coumaryl alcohol, caffeyl alcohol, coniferyl alcohol and sinapyl alcohol, and have physiological, ecological and biomedical significance. While it is necessary to investigate the biological pathways and economic value of these alcohols, research is hindered because of their limited availability and high cost. Traditionally, these alcohols are obtained by chemical synthesis and plant extraction. However, synthesis by biotransformation with immobilized microorganisms is of great interest because it is environmentally friendly and offers high stability and regenerable cofactors. Therefore, we produced 4-hydroxycinnamyl alcohols using immobilized whole cells of engineered Escherichia coli as the biocatalyst.

Results

In this study, we used the recombinant E. coli strain, M15–4CL1–CCR, expressing the fusion protein 4-coumaric acid: coenzyme A ligase and the cinnamoyl coenzyme A reductase and a recombinant E. coli strain, M15–CAD, expressing cinnamyl alcohol dehydrogenase from Populus tomentosa (P. tomentosa). High performance liquid chromatography and mass spectrometry showed that the immobilized whole cells of the two recombinant E. coli strains could effectively convert the phenylpropanoic acids to their corresponding 4-hydroxycinnamyl alcohols. Further, the optimum buffer pH and the reaction temperature were pH 7.0 and 30 °C. Under these conditions, the molar yield of the p-coumaryl alcohol, the caffeyl alcohol and the coniferyl alcohol was around 58, 24 and 60%, respectively. Moreover, the highly sensitive and selective HPLC–PDA–ESI–MSn method used in this study could be applied to the identification and quantification of these aromatic polymers.

Conclusions

We have developed a dual-cell immobilization system for the production of 4-hydroxycinnamyl alcohols from inexpensive phenylpropanoic acids. This biotransformation method is both simple and environmental-friendly, which is promising for the practical and cost effective synthesis of natural products.Graphical abstract

One-pot conversion of cephalosporin C by using an optimized two-enzyme process

Setup of a low cost one-pot enzymatic system to directly convert cephalosporin C into 7-aminocephalosporanic acid with high purity.

Microbial production of 7-amino-cephalosporanic acid and new generation cephalosporins (cephalothin) by different processing strategies

The development of beta-lactam antibiotics has been a continuous battle of the design of new compounds to withstand inactivation by the ever-increasing diversity of beta-lactamases. Semisynthetic cephalosporins like cephalothin were synthesized from 7-amino-cephalosporanic acid (7-ACA), and thiophene-2-acetic acid using cephalosporin-C acylase enzyme was studied. The production of cephalosporin-C acylase by Pseudomonas diminuta was used and the growth kinetics studied. The optimum condition of enzyme activity was determined by using response surface methodology. A 2(3) full-factorial composite design was employed for experimental design and the result analyzed. The pH value and temperature for optimum activity were 6.5 and 32 degrees C, respectively. The structural analog compound similar to the side-chain of semisynthetic cephalosporins, e.g., thiophene-2-acetic acid, was added. HPLC data analysis indicate that the concentration of cephalothin was 1.6 mg/mL.

Reusability of entrapped cells of Pseudomonas diminuta for production of 7-aminocephalosporanic acid

Entrapped cells of P. diminuta were used for the production of 7-aminocephalosporanic acid (7-ACA), a key intermediate required for the production of most of the clinically used cephalosporin derivatives, i.e., semisynthetic cephalosporins. The repeated batch production of 7-ACA with entrapped cells of P. diminuta in different carriers were carried out for six cycles at optimal conditions. It was found that 33% , 38%, and 47% of activity was lost with chitosan, gelatin, and agar, respectively as immobilizing supports after the sixth cycle of operation.