Mutagenic effect of acridine orange on the expression of penicillin G acylase and beta-lactamase in Escherichia coli

Exploitation of E. coli for the production of penicillin G amidase: a tool for the synthesis of semisynthetic β-lactam antibiotics

BACKGROUND

Penicillin G amidase/acylases from microbial sources is a unique enzyme that belongs to the N-terminal nucleophilic hydrolase structural superfamily. It catalyzes the selective hydrolysis of side chain amide/acyl bond of penicillins and cephalosporins whereas the labile amide/acyl bond in the β-lactam ring remains intact. This review summarizes the production aspects of PGA from various microbial sources at optimized conditions. The minimal yield from wild strains has been extensively improved using varying strain improvement techniques like recombination and mutagenesis; further applied for the subsequent synthesis of 6-aminopenicillanic acid, which is an intermediate molecule for synthesis of a wide range of novel β-lactam antibiotics. Immobilization of PGA has also been attempted to enhance the durability of enzyme for the industrial purposes.

SHORT CONCLUSION

The present review provides an emphasis on exploitation of E. coli to enhance the microbial production of PGA. The latest achievements in the production of recombinant enzymes have also been discussed. Besides E. coli, other potent microbial strains with PGA activity must be explored to enhance the yields.

Graphene based nanoassembly for simultaneous detection and degradation of harmful organic contaminants from aqueous solution

Graphene based nanoassemblies that can simultaneously detect and degrade harmful organic contaminants from water are important for conquering the risk of hazardous chemicals.

Improvement of penicillin G acylase expression in Escherichia coli through UV induced mutations

We used ultraviolet (UV) radiation to induce mutation in three locally isolated strains of Escherichia coli. Different dilutions of bacterial cultures were exposed to UV lamp of 254 nm wavelength for different time intervals at varied distances ranging from 5 to 210 sec and 5 to 100 cm. Viable colonies were screened for mutants with an increased production of penicillin G acylase (PGA) and a reduced production of β-lactamase, which are the desired properties of PGA producing industrial strains. A survival curve was made to get optimum exposure time and distance. The survival percentage for each exposure period was calculated and 1-5% survival was found useful for obtaining mutants with desired change. Screening for PGA and β-lactamase constitutive and/or deficient mutants was made by Serratia marcescens overlay test. A total of 100 survivors were selected of which 49% expressed PGA activity higher than the parent strain. Frequency of β-lactamase constitutive and deficient mutants was 48 and 52%, respectively. The best hyper-producing mutant (BDCS-N-M74), with almost negligible expression of β-lactamase, exhibited three-fold (22.5 mg 6-APA h(-1) mg(-1) wet cells) increase in PGA activity compared with that in the parent strain (6.7 mg 6-APA h(-1) mg(-1) wet cells). The results indicated the successful induction of UV mediated mutation in E. coli for PGA hyper-producing mutants lacking β-lactamase activity.

Assessment of acridine orange and SYTO 16 for in vivo imaging of the peritoneal tissues in mice

The effect of peritoneal injection of acridine orange and SYTO 16 in mice was investigated. Images of peritoneal tissues stained with these dyes and obtained through a confocal micro-endoscope are presented. Seventy-five Balb/c mice were split into five groups and given peritoneal injections of dye or saline. The proportions of negative outcomes in each group were compared using confidence intervals and the Fisher's exact statistical test. A statistically significant increase in adverse events due to dye injection was not observed. These data provide an initial investigation into the safety of acridine orange and SYTO 16 for in vivo imaging.

Comparative production of 6-aminopenicillanic acid by different E. coli strains and their acridine orange (AO) induced mutants

The present study was conducted to see the difference in production of 6-APA I) between wild strains of E. coli collected from local environment and their acridine orange (AO) induced mutants and ii) between mutants and E. coli strains (ATCC 11105 and ATCC 9637) of American Type Culture Collection (ATCC) used commercially for enzymatic production of 6-APA. The optimum conditions for bioconversion were standardized and 6-APA was obtained in crystalline form. Relative PGA activity of local and foreign E. coli strains varied significantly with the highest being 12.7 in mutant strain (BDCS-N-M36) and the lowest 4.3 mg 6-APA h(-1) mg(-1) wet cells in foreign strain (ATCC 11105). The enzyme activity exhibited by mutant strain (BDCS-N-M36) was also two folds higher compared to that in wild parent BDCS-N-W50 (6.3 mg 6-APA h(-1) mg(-1) wet cells). The overall production of 6-APA and conversion ratios ranged between 0.25-0.41 g of 6-APA per 0.5 g of penicillin G and 51-83%, respectively. Maximum conversion ratio (83%) was achieved by using crude cells of mutant strain (BDCS-N-M36) which is the highest value ever reported by crude cells on a shake-flask scale whereas reported 6-APA production by immobilized cells is 60-90% in batch and continuous systems. Results are being discussed with reference to importance of local bacterial strains and their significance for industrially important enzymes.