Chromium toxicity is one of the major causes of environmental pollution due to its heavy discharge in industrial wastewaters. Chromate reduction is a viable method to detoxify hexavalent chromium to nontoxic trivalent species mediated by enzymes and metabolites. A new Bacillus methylotrophicus strain was isolated from tannery sludge and was an efficient candidate for chromate reduction. An initial chromate reductase activity of 212.84 U/mg protein was obtained at 48 h in a low-cost defined medium formulation with 0.25 mM chromate. The extracellular enzyme was inducible at 12h substrate addition with 312.99 U/mg at 48 h. Reduced glutathione was required for enhanced specific activity of 356.48 U/mg. Enzyme activity was optimum at pH 7.0 and at 30 °C, and was stable in the presence of EDTA, DTT and metal ions. The enzyme exhibited a Vmax of 59.89 μM/min/mg protein and a Km of 86.5 μM, suggesting feasibility of the reaction with K₂Cr₂O₇ as substrate. Application of the crude reductase in tannery effluent resulted in 91.3% chromate reduction at 48 h. An enzyme-mediated chromate reduction process has therefore been developed for bioremediation of toxic chromium sp. in industrial effluents.
Nanotechnology has made a tremendous impact over a period of three decades in various facets of industrial and medical sectors and still find recent interests to exploit their characteristics for commercial applications. Nanobiotechnology is a field of using nanomaterials for biological applications. The preparation of nanomaterials from biological sources has been known as 'green' technology. Nanoparticles measure in the size range of 1-100 nm and possess unique characteristics than their bulk materials with potential applications in various biological, medical, industrial, agricultural and ecological fields. Using nanoparticles in antimicrobial applications has been explored since the early years of Nanotechnology development. However, few reports exist on the mechanisms of antimicrobial actions mediated by nanoparticles and their effects on environment and ecosystems. Several factors affect the antimicrobial properties of nanoparticles, which are quite important to understand the roles of their antimicrobial action. This review is aimed to discuss the antibacterial properties, the mechanisms and antimicrobial applications of Nanoparticles in medicine and allied areas. We have suggested that despite the several applications of nanomaterials, their production by biological methods and suitable applications also need to focus on the toxicity implications. Nanomaterial toxicity in the ecological niche is of significant concern and regulatory bodies should be organized to evaluate the successful use of nanomaterials for a wide variety of applications. The review significantly summarizes hot topics of interest in antibacterial activities, mode of action, biomedical applications of nanoparticles, their metabolic fate in vivo and toxicity effects in humans for further consideration of researches in Microbial Nanotechnology.
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