Vinod Kumar Nigam

Nitrilase-catalysed conversion of acrylonitrile by free and immobilized cells of Streptomyces sp.

The biotransformation of acrylonitrile was investigated using thermophilic nitrilase produced from a new isolate Streptomyces sp. MTCC 7546 in both the free and immobilized state. Under optimal conditions, the enzyme converts nitriles to acids without the formation of amides. The whole cells of the isolate were immobilized in agar-agar and the beads so formed were evaluated for 25 cycles at 50°C. The enzyme showed a little loss of activity during reuse. Seventy-one per cent of 0.5 M acrylonitrile was converted to acid at 6 h of incubation at a very low density of immobilized cells, while 100% conversion was observed at 3 h by free cells.

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.

Extraction of bulk DNA from Thar Desert soils for optimization of PCR-DGGE based microbial community analysis

Electronic Journal of Biotechnology ISSN: 0717-3458 Vol.10 No.3, Issue of July 15, 2007

Extracellular facile biosynthesis, characterization and stability of gold nanoparticles by Bacillus licheniformis

Abstract Context: The development of a reliable, eco-friendly process for synthesis of gold nanoparticles (AuNPs) has gained impetus in recent years to counter the drawbacks of chemical and physical methods. Objective: This study illustrates simple, green synthesis of AuNPs in vitro using cell lysate supernatant (CLS) of non-pathogenic bacteria and to investigate its potential antimicrobial activity. Materials and methods: Gold nanoparticles were synthesized by the reduction of precursor AuCl4− ions using the CLS of Bacillus licheniformis at 37°C upon 24 h of incubation. The nanoparticles were characterized for their morphology, particle size, optical absorption, zeta potential, and stability. Further the antimicrobial activity was assayed using cup-plate method. Results: The process of biosynthesis was extracellular and the gold ions were reduced to stable nanogold of average size 38 nm. However, upon storage of AuNPs for longer duration at room temperature stability was influenced in terms of increase in particle size and decrease in zeta potential with respect to as synthesized nanoparticles. SEM micrographs revealed the spherical shape of AuNPs and EDX analysis confirmed the presence of gold in the sample. Also clear zone of inhibition was observed against Bacilllus subtilis MTCC 8364, Pseudomonas aeruginosa MTCC 7925, and Escherichia coli MTCC 1698 confirming the antimicrobial activity of AuNPs. Discussion: The bioprocess under study was simple and less time consuming as compared to other methods as the need for harvesting AuNPs from within the microbial cells via downstream process will be eliminated. Nanoparticles exhibited good stability even in absence of external stabilizing agents. AuNPs showed good antimicrobial activity against several Gram-negative and Gram-positive pathogenic bacteria. Conclusion: The extracellular biosynthesis from CLS may serve as a suitable alternative for large scale synthesis of gold nanoparticles in vitro. The synthesis from lysed bacterial cell strongly suggests that exposure of microbial whole cells to the gold solution for nanoparticle formation is not necessary and that microorganism even in lysed state retained its bioreduction potential. Further the potential of biologically synthesized AuNPs as antimicrobial agents will be of great commercial importance.

Enzyme Based Biosensors for Detection of Environmental Pollutants--A Review.

Environmental security is one of the major concerns for the safety of living organisms from a number of harmful pollutants in the atmosphere. Different initiatives, legislative actions, as well as scientific and social concerns have been discussed and adopted to control and regulate the threats of environmental pollution, but it still remains a worldwide challenge. Therefore, there is a need for developing certain sensitive, rapid, and selective techniques that can detect and screen the pollutants for effective bioremediation processes. In this perspective, isolated enzymes or biological systems producing enzymes, as whole cells or in immobilized state, can be used as a source for detection, quantification, and degradation or transformation of pollutants to non-polluting compounds to restore the ecological balance. Biosensors are ideal for the detection and measurement of environmental pollution in a reliable, specific, and sensitive way. In this review, the current status of different types of microbial biosensors and mechanisms of detection of various environmental toxicants are discussed.

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

Statistical optimization of medium components to increase the manganese peroxidase productivity by Phanerochaete chrysosporium NCIM 1197

The production of manganese peroxidase (MnP) by the white-rot fungus Phanerochaete chrysosporium NCIM 1197 was investigated by the screening and optimization of the media constituents and physiological factors. MnP production by the fungus was used as the response to screen the media constituents with statistically valid Plackett-Burman (P-B) design. Response surface methodology (RSM) was applied to optimize the level of screened media constituents. Amongst the media constituents screened, glucose, maltose, ammonium chloride, and urea were selected as the most important for MnP enhancement. A five-level Central Composite Design (CCD) was used in optimizing the important media constituents for maximizing the MnP production. The optimal medium composition for maximum MnP production was 13.88 mM of glucose, 13.88 mM of maltose, 0.02 mM of ammonium chloride, and 0.02 mM of urea. The final experiment was conducted to validate the model, which was shown to produce 70.20 U/mL of MnP with a predicted value of 66.49 U/mL on the 8th day of incubation.

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.

Bioengineering of Nitrilases Towards Its Use as Green Catalyst: Applications and Perspectives

Nitrilases are commercial biocatalysts used for the synthesis of plastics, paints, fibers in the chemical industries, pharmaceutical drugs and herbicides for agricultural uses. Nitrilase hydrolyses the nitriles and dinitriles to their corresponding carboxylic acids and ammonia. They have a broad range of substrate specificities as well as enantio-, regio- and chemo-selective properties which make them useful for biotransformation of nitriles to important compounds because of which they are considered as ‘Green Catalysts’. Nitriles are widespread in nature and synthesized as a consequence of anthropogenic and biological activities. These are also present in certain plant species and are known to cause environmental pollution. Biotransformation using native organisms as catalysts tends to be insufficient since the enzyme of interest has very low amount in the total cellular protein, rate of reaction is slow along with the instability of enzymes. Therefore, to overcome these limitations, bioengineering offers an alternative approach to alter the properties of enzymes to enhance the applicability and stability. The present review highlights the aspects of producing the recombinant microorganisms and overexpressing the enzyme of interest for the enhanced stability at high temperatures, immobilization techniques, extremes of pH, organic solvents and hydrolysing dintriles to chiral compounds which may enhance the possibilities for creating specific enzymes for biotransformation.

Antioxidant and antibacterial hydroxyapatite-based biocomposite for orthopedic applications

Post-implantation, vicinity acquired oxidative stress and bacterial infections lead to apoptosis with eventual bone-resorption and implant failure, respectively. Thus, in order to combat aforementioned complications, present research aims in utilizing antioxidant ceria (CeO2) and antibacterial silver (Ag) reinforced hydroxyapatite (HA) composite with enhanced mechanical and cytocompatible properties. Highly dense (>90%) spark plasma sintered HA-based composites elicits enhanced elastic modulus (121-133 GPa) in comparison to that of HA. The antioxidant activity is quantified using ceria alone, wherein HA-ceria and HA-ceria-Ag pellets exhibits ~36 and 30% antioxidant activity, respectively, accrediting ceria as a scavenger of reactive oxygen species, which was corroborated with the % Ce3+ change quantified by X-ray photoelectron spectroscopy. The HA-Ag pellet shows antibacterial efficacy of ~61% for E. coli and ~53% for S. aureus, while a reduction of ~59% for E. coli and ~50% for S. aureus is observed for HA-ceria-2.5Ag pellet, affirming Ag reinforcement as an established bactericidal agent. The enhanced hydrophobicity on all the HA-based composites affords a high protein adsorption (24 h incubation). Further, elevated hFOB cell count (~6.7 times for HA-ceria-Ag on day 7) with filopodial extensions (60-150 μm) and matrix-like deposition reflect cell-substrate intimacy. Thus, synergistic antioxidant ceria and antibacterial Ag reinforcement with enhanced mechanical integrity can potentially serve as cytocompatible porous bone scaffolds or bioactive coatings on femoral stems.