Subir Kundu

Trace analysis of cefotaxime at carbon paste electrode modified with novel Schiff base Zn(II) complex.

Cefotaxime a third generation cephalosporin drug estimation in nanomolar concentration range is demonstrated for the first time in aqueous and human blood samples using novel Schiff base octahedral Zn(II) complex. The cefotaxime electrochemistry is studied over graphite paste and Zn(II) complex modified graphite paste capillary electrodes in H(2)SO(4) (pH 2.3) using cyclic voltammetry and differential pulse voltammetry. Cefotaxime enrichment is observed over Zn(II) complex modified graphite paste electrode probably due to interaction of functional groups of cefotaxime with Zn(II) complex. Possible interactions between metal complex and cefotaxime drug is examined by UV-vis and electrochemical quartz crystal microbalance (EQCM) techniques and further supported by voltammetric analysis. Differential pulse voltammetry (DPV) with modified electrode is applied for the determination of cefotaxime in acidified aqueous and blood samples. Cefotaxime estimation is successfully demonstrated in the range of 1-500 nM for aqueous samples and 0.1-100 microM in human blood samples. Reproducibility, accuracy and repeatability of the method are checked by triplicate reading for large number of samples. The variation in the measurements is obtained less than 10% without any interference of electrolyte or blood constituents.

Fast-growing, non-infectious and intracellularly surviving drug-resistant Mycobacterium aurum: a model for high-throughput antituberculosis drug screening

OBJECTIVES Enoyl acyl-carrier-protein reductase (InhA), the primary endogenous target for isoniazid and ethionamide, is crucial to type-II fatty acid biosynthesis (FAS-II). The objectives of this study were first to generate InhA mutants of Mycobacterium aurum, secondly to characterize InhA-mediated isoniazid and ethionamide resistance mechanisms across those mutants and finally to investigate the interaction of InhA with enzymes in the FAS-II pathway in M. aurum. METHODS Spontaneous mutants were generated by isoniazid overdose and limited broth dilution, while for genetically modified mutants sense-antisense DNA technology was used. Southern hybridization and immunoprecipitation were both used to identify the InhA homologue in M. aurum. The latter method was further used to compare the level of InhA expression in M. aurum with that in corresponding mutants. Isoniazid/ethionamide susceptibility modulation was examined in vitro and ex vivo using a resazurin assay as well as by cfu counting. In addition, circular dichroism and the bacterial two-hybrid system were exploited to investigate the interaction of InhA with other enzymes of the FAS-II pathway. RESULTS A Mycobacterium tuberculosis InhA homologue was detected in M. aurum. Susceptibility to isoniazid/ethionamide was significantly altered in genetically modified mutants and simultaneously InhA was overexpressed in both spontaneous and genetically modified mutants. InhA interacts with other FAS-II enzymes of M. aurum in vivo. CONCLUSION Close resemblance of isoniazid/ethionamide action on InhA between M. tuberculosis and M. aurum further supports the use of fast-growing and intracellularly surviving drug-resistant M. aurum to substitute for highly virulent, extremely slow-growing M. tuberculosis strains in the early stage of antituberculosis inhibitor screening.

Studies on cephalosporin-C production in an air lift reactor using different growth modes of Cephalosporium acremonium

This paper deals with the studies on Cephalosporin-C production in a lab-scale airlift reactor using Cephalosporium acremonium. Various growth modes, viz. pellets and Siran supported bioparticles were used to improve the process over conventional free mycelial fermentation. Cephalosporin-C production was significantly improved by using bioparticles over the free mycelial culture, probably due to the enhanced mass transfer in the fermentation broth. However, the biofilm of the bioparticles became unstable as the fermentation proceeded, and increase in the free cells in the broth occurs. The maximum specific growth rate of free cells, pellets and Siran carrier were observed to be 0·037, 0·033 and 0·045 h−1, respectively. The oxygen transfer coefficient also improved for the immobilised modes (100 h−1, 70 h−1 for Siran carrier and pellets) and thereby enhanced specific antibiotic productivity, 18–28% were observed.

Development of Probiotic Candidate in Combination with Essential Oils from Medicinal Plant and Their Effect on Enteric Pathogens: A Review

Medicinal plants and probiotics both have very high potential in terms of their antimicrobial activity against antibiotic-resistant enteric pathogens. The probiotics being enteric microorganism do not have any parasitic effect on human beings. They have been an integral part of daily food for centuries. They have been shown to have health beneficiary properties. The probiotics retard the growth of the microorganisms, while essential oil kills them. Combining the effect of medicinal plant extract and probiotics may be a new approach due to their complementary antimicrobial effects and practically no side effects. The synergistic effect of the essential oil and probiotics will be necessarily higher than using them alone as health product.

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

Abstract7-Aminocephalosporanic acid (7-ACA), the starting material for the production of a number of clinically used semisynthetic cephalosporins, is produced by deacylation of cephalosporin-C. The production of 7-ACA was studied in various modes, at the optimal conditions using free and immobilized whole cells of Pseudomonas diminuta.

Studies on Cephalosporin-C production using immobilised cells of Cephalosporium acremonium in a packed bed reactor

Abstract The production of the β-lactam antibiotic, Cephalosporin-C in a packed bed bioreactor was studied using Cephalosporium acremonium immobilised in calcium alginate, bagasse, and silk sachets. The specific β-lactam antibiotic production rate of immobilised cells was about 120%, 125% and 133% at 100 h (free cells 100%) for calcium alginate, bagasse and silk sachets, respectively. A cells-to-carrier ratio of 3:2 was found to be optimum throughout these studies. The effect of recycle ratio indicated diffusion barriers to substrate transport.

Bioconversion of silver salt into silver nanoparticles using different microorganisms.

Abstract: Recently, silver nanoparticles have generated enough interest due to their immense usage. Until now chemical synthesis has been a fast method to produce nanoparticles, but the release of environmental pollutants has raised caution. So a more subtle biochemical approach is in research. Three microorganisms, Aspergillus flavus, Phoma exigua and Bacillus megaterium, were selected to reduce silver nitrate to silver nanoparticles in aqueous form. All three microorganisms showed varying reducing capacity, of which Phoma exigua showed the highest, when their biomass was incubated in silver nitrate for 48 hours. The nanoparticles showed all the optical and physical properties, which were analyzed by measuring the surface plasmon resonance and TEM. It was also observed that the fungal species have varied growth in silver nitrate and can be used to produce silver nanoparticles, directly incubating the inoculums of fungus in the media containing silver nitrate. On comparing all the characteristics and results produced, Aspergillus flavus was found to be the most effective microorganism, which can convert the silver nitrate to silver nanoparticles in aqueous condition. The bacterial species showed no growth with incubation with silver nitrate.

Influence of medium constituents on the biosynthesis of cephalosporin-C

Electronic Journal of Biotechnology ISSN: 0717-3458 Vol.10 No.2, Issue of April 15, 2007

Continuous Production of Cephalosporin‐C by Immobilized Microbial Cells Using Symbiotic Mode in a Packed Bed Bioreactor

Cephalosporins are usually produced semisynthetically from Cephalosporin‐C, which is exclusively produced by Cephalosporium acremonium. Free cell studies for the production of Cephalosporin‐C had some limitation such as pulpy growth of fungus causing an appreciable rise in the broth viscosity affecting the transfer of oxygen and other nutrients into the cells. High cell concentrations cannot be maintained because of wash out phenomenon at high dilution rates. The whole cell immobilization technique is a potentially important process for Cephalosporin‐C biosynthesis, where increase cell densities were maintained and broth‐handling problems were reduced. Cephalosporin‐C fermentation is a highly aerobic process. The symbiotic relationship of Cephalosporium acremonium and Chlorella pyrenoidosa has been used to increase oxygen transfer rate to the fungi by co‐immobilizing it with algae. Co immobilization of whole cells of fungus and algae were carried out in different immobilizing agents and the systems were coated with polyacrylamide resin of pharmaceutical grade to overcome the problems of leakage. The operational stability of immobilized systems in a packed bed reactor was also studied.

Graphene Quantum Dots - From Emergence to Nanotheranostic Applications

Quantum dots are at the cutting edge of nanotechnology development. Due to their unique optical and physical properties, they have potential applications in many avenues of medicine and biotechnology. With the advancements in nano-sciences, novel applica‐ tions of quantum dots are constantly being explored for drug delivery and bioimaging. Graphene quantum dots (GQDs) are nanoparticles of graphene with properties of quan‐ tum dots as well as graphene. GQDs have ignited remarkable research interest in the field of medicine and biology and are considered as well-suited candidates for nanothera‐ nostic applications due to their excellent biocompatibility and tunable physicochemical properties. The promising emerging implications of GQD platforms for diagnostics and therapeutics advances are the basis of this chapter.