Assessment of surface water of Gulf of Kachchh, west coast of India: A chemometric approach.

The present study is aimed at investigation of surface water quality of Gulf of Kachchh (GoK), Gujarat. The main objective of this study was to convert complex dataset of water quality parameters from GoK into comprehensive, simple and interpretable observations. Hence, physico-chemical parameters and nutrients of surface water from GoK were analyzed. Chemometric results indicated that oxygen, salinity, dissolved solids, nutrient and natural conditions were the factors that affected surface water quality. The water quality index was calculated to identify water quality classes to evaluate the spatio-seasonal trend in the study area. The results revealed that water quality was moderate in summer, worst in pre-monsoon and best in post-monsoon. The study also highlighted that Marine National Park (Central GoK) was observed to be comparatively in good condition with abundant marine biodiversity. Thus, the results of chemometric study of water quality parameters can be a valuable tool for government authorities for sustainable development of GoK.

Characterization of L-asparaginase from marine-derived Aspergillus niger AKV-MKBU, its antiproliferative activity and bench scale production using industrial waste.

L-asparaginase (LA), an enzyme with anticancer activities, produced by marine-derived Aspergillus niger was subjected to purification and characterization. The purified enzyme was observed to have molecular weight ∼90KDa. The enzyme retained activity over a wide range of pH, i.e. pH 4-10. The enzyme was quite stable in temperature range 20-40°C. Tween 80 and Triton X-100 were observed to enhance LA activity while inhibition of LA activity was observed in presence of heavy metals. The values for Km was found to be 0.8141 mM and Vmax was 6.228µM/mg/min. The enzyme exhibited noteworthy antiproliferative activity against various cancer cell lines tested. Successful bench scale production (in 5L bioreacator) of LA using groundnut oil cake as low cost substrate has also been carried out.

Influence of antibiotic adsorption on biocidal activities of silver nanoparticles.

Excessive use of antibiotics has posed two major challenges in public healthcare. One of them is associated with the development of multi-drug resistance while the other one is linked to side effects. In the present investigation, the authors report an innovative approach to tackle the challenges of multi-drug resistance and acute toxicity of antibiotics by using antibiotics adsorbed metal nanoparticles. Monodisperse silver nanoparticles (SNPs) have been synthesised by two-step process. In the first step, SNPs were prepared by chemical reduction of AgNO3 with oleylamine and in the second step, oleylamine capped SNPs were phase-transferred into an aqueous medium by ligand exchange. Antibiotics - tetracycline and kanamycin were further adsorbed on the surface of SNPs. Antibacterial activities of SNPs and antibiotic adsorbed SNPs have been investigated on gram-positive (Staphylococcus aureus, Bacillus megaterium, Bacillus subtilis), and gram-negative (Proteus vulgaris, Shigella sonnei, Pseudomonas fluorescens) bacterial strains. Synergistic effect of SNPs on antibacterial activities of tetracycline and kanamycin has been observed. Biocidal activity of tetracycline is improved by 0-346% when adsorbed on SNPs; while for kanamycin, the improvement is 110-289%. This synergistic effect of SNPs on biocidal activities of antibiotics may be helpful in reducing their effective dosages.

Antibacterial activities of silver nanoparticles and antibiotic-adsorbed silver nanoparticles against biorecycling microbes.

Silver nanoparticles have a huge share in nanotechnology based products used in clinical and hygiene products. Silver nanoparticles leaching from these medical and domestic products will eventually enter terrestrial ecosystems and will interact with the microbes present in the land and water. These interactions could be a threat to biorecycling microbes present in the Earth's crust. The antimicrobial action towards biorecycling microbes by leached silver nanoparticles from medical waste could be many times greater compared to that of silver nanoparticles leached from other domestic products, since medical products may contain traditional antibiotics along with silver nanoparticles. In the present article, we have evaluated the antimicrobial activities of as-synthesized silver nanoparticles, antibiotics - tetracycline and kanamycin, and antibiotic-adsorbed silver nanoparticles. The antimicrobial action of silver nanoparticles with adsorbed antibiotics is 33-100% more profound against the biorecycling microbes B. subtilis and Pseudomonas compared to the antibacterial action of silver nanoparticles of the same concentration. This study indicates that there is an immediate and urgent need for well-defined protocols for environmental exposure to silver nanoparticles, as the use of silver nanoparticles in nanotechnology based products is poorly restricted.

Antibacterial activity of silver: the role of hydrodynamic particle size at nanoscale.

Silver shows the highest antimicrobial activities amongst all metals. It is better than many first line antibiotics. The antimicrobial properties of silver can be tuned by altering its physical and surface properties. Researchers have demonstrated enhancement in the antibacterial properties of silver with decreasing particle size from bulk to nano. In the present article, we study the effect of particle size of silver at nanoscale on their antimicrobial properties. Two samples of silver nanoparticles (SNPs) of same physical size (≈8 nm) but different hydrodynamic size (59 and 83 nm) are prepared by chemical reduction of AgNO3 with oleylamine followed by phase transfer with triblock copolymer Pluronic F-127. Their antimicrobial properties are investigated by microdilution method against clinically important strains of gram positive (S. aureus and B. megaterium) and gram negative (P. vulgaris and S. sonnei) bacteria. Nearly 38-50% enhancement in the antibacterial action of SNPs was observed when their hydrodynamic size was reduced to 59 nm from 83 nm. It has been observed that the antibacterial action of SNPs was governed by their hydrodynamic size and not by their crystallite and physical size. The phenomenological model was also proposed which makes an attempt to explain the microscopic mechanism responsible for the size dependent antibacterial activities of silver.

In silico protein structure modeling and conservation analysis of ChrR, a class-i chromate reducing flavoenzyme from Pseudomonas putida.

Hexavalent chromium [Cr(VI)] is a widespread environmental pollutant, arising as a by-product of numerous industrial processes. Bacteria can reduce toxic and carcinogenic Cr(VI) to insoluble and less toxic Cr(III), offering promise for an environmental friendly and affordable solution to chromate pollution. ChrR, a class I chromate-reducing flavoenzyme from Pseudomonas putida is an efficient chromate reducer. The crystal structure of ChrR is yet unknown to the scientific community, hence a three-dimensional (3D) structure is very essential for structural studies, protein - ligand interaction simulations and designing novel bioremediation strategies. The 3D model of the P. putida ChrR protein was predicted using in silico approach. Due to low percentage of sequence identity for homology modeling, I-TASSER was used for structure prediction which combines the methods of threading, ab initio modeling and structural refinement. The stereo chemical quality of the best model was validated with 90.6% residues under favored region from Ramachandran plot. The modeled protein was submitted to Protein Model Database and can be downloaded with the ID PM0077375. The degree of conservation was mapped onto the predicted model and ligand binding sites were found. The results of conservation analysis and binding site prediction were combined to show several highly conserved binding sites. Altogether, the structure for ChrR has been predicted. The work reveals novel universally conserved residues. These residues could be candidates for binding interactions and provide the basis for designing advanced chromium bioremediation strategies.

Tolerance and removal of arsenic by a facultative marine fungus Aspergillus candidus.

The objective of the work was to investigate tolerance to and removal of arsenic by a facultative marine fungus Aspergillus candidus. The fungus showed luxuriant growth in different concentrations (25 and 50mg/L) of trivalent and pentavalent forms of arsenic. Biomass accumulation data substantiate tolerance of A. candidus towards the test concentrations of trivalent and pentavalent forms of arsenic. Highest arsenic removal (mg/g) was recorded on day 3. As removal increased with an increase in concentration. Hence, the test fungus A. candidus is a promising candidate for arsenic remediation.

Chemical characterization and quantification of siderophores produced by marine and terrestrial aspergilli.

Ten aspergilli (five each from marine and terrestrial habitats) were screened for siderophore production. All test isolates produced siderophores as indicated by a positive reaction in the FeCl(3) test, chrome azurol sulphonate assay, and chrome azurol sulphonate agar plate test. Further, the test isolates were compared for their siderophore production potential and chemical characteristics. Examination of the chemical nature of the siderophores revealed that all test isolates produced hydroxamate siderophores that were trihydroxamate hexadentates. Wide-spread occurrence of siderophores in marine isolates indicate their functional role in maintaining overall productivity of coastal waters. Among all test aspergilli, marine Aspergillus versicolor was found to be the largest siderophore producer (182.5 microg/mL desferrioxamine mesylate equivalent), least siderophore production was recorded in a marine strain of Aspergillus niger (3.5 microg/mL desferrioxamine mesylate equivalent).

Tolerance and accumulation of hexavalent chromium by two seaweed associated aspergilli.

Marine seaweed (Eucheuma sp.) associated strains of Aspergillus flavus and Aspergillus niger were tested for their Cr(VI) tolerance. Both the isolates showed luxuriant growth in different concentrations of Cr(VI), i.e., 25, 50 and 100 ppm. There was no marked variation in the dry weight of control and test isolates, which indicated that both the isolates can tolerate a wide range of hexavalent chromium and their application for bioremediation purpose can be envisaged as XRF data revealed both the isolates accumulated more than 25% of the chromium supplied. A. flavus invariably exhibited higher accumulation potential.