Biochemical Leaching of Metals from Indian Ocean Nodules

Bioleaching of valuable metals from Indian Ocean poly-metallic nodules was carried out using a pure culture of Aspergillus niger. Parameters such as pH, pulp density (PD), particle size, time were optimised for the bio-recovery of metals. At pH 4.5, 35 °C temperature and 5% PD and in 30 days the biorecovery of the metals was found to be 97% Cu, 98% Ni, 86% Co, 91% Mn and 32% Fe whereas in control experiment 4.9% Cu, 8.2% Ni, 27% Co, 6.3% Mn and 7.1% Fe were dissolved. The interesting aspect of this investigation is that a good amount of leached metals are adsorbed on fungal mycelia which can be recovered by acid wash. Fall in pH rom 7 to 4.6 and rise in Eh from 140 mV to 380 mV indicated that A.niger followed indirect leach-ing mechanism by releasing some organic acids which in turn converted higher oxides to lower oxide phases as identified by XRD phase analyses

Potential Application of a Heterotrophic Microorganism for Bioleaching of Metals from Indian Ocean Nodules

Bacillus circulans, a heterotrophic microorgansim has been used for the recovery of copper, nickel and cobalt from sea nodules. The organism was revived in nutrient medium and adapted gradually on sea nodules prior to leaching. Bioleaching studies were carried out in shake flasks containing sea nodule powder with growth medium and adapted microbial culture under a range of conditions such as pH, pulp density, particle size of nodules and temperat-ure. Metal recovery was highest in 30 days but the rate of recovery was slow after 25 days of bioleaching. A 92% Cu, 73% Ni, 72% Co, 38% Mn and 17% Fe was recovered at pH 2 in 25 days at 35°C temperature. XRD identification of residue showed the presence of some lower and mixed oxidation phases of manganese and some unaltered iron phases. The biodissolution of metals was direct enzyme leading to reduction of Mn (IV) to Mn (II) and Fe (III) to Fe (II)

Yb(III), Sm(III) and La(III) complexes of a tetradentate pyridoxal Schiff base ligand: their DNA-binding activity and bio-imaging applications

Yb(III), Sm(III) and La(III) complexes of a tetradentate Schiff base ligand, bis(pyridoxylidene)ethyelenediamine, are reported. Single crystal X-ray crystal structures of the complexes reveal that in all of them the Ln(III) ions are in a distorted dodecahedral geometry with N4O4-coordination environment provided by two coordinated ligands. Fluorescence spectroscopy shows that in the Yb(III) and Sm(III) complexes energy transfer from ligand centered excited state leads to population of emissive f-f excited states. The reported complexes bind to ct-DNA, with high binding constant (Kb) comparable to those which bind by intercalative mode. Cytotoxicity study shows that the complexes have quite low cytotoxicity towards HeLa cell. Further, they exhibited fast response, bright fluorescence and stability at physiological pH, making them suitable for use in fluorescence bio-imaging

A review on biological control and metabolism of aflatoxin

The series of events that led to the discovery of aflatoxin as a potent carcinogen, its biosynthesis, mechanism of action, structure-function relationship provide interesting insight into the economical and technological factors involved in the development of an effective control measure for the toxin. Scientists all over the world are making continuous efforts to explore a generalized process of detoxification, which can bring down the toxin content in heterogeneous commodities to a threshold level. hi this article biological control methods with special emphasis on in vivo and in vitro enzymatic detoxification of aflatoxin have been reviewed. Future areas of research involving large-scale enzymatic detoxification and modified atmosphere storage are also discussed

Leaching of copper, nickel and cobalt from Indian Ocean manganese nodules by Aspergillus niger

The leaching of copper, nickel and cobalt from polymetallic manganese nodules from the Indian Ocean was investigated using a fungus Aspergillus niger. Parameters such as initial pH, pulp density, particle size and duration of leaching were optimized for the bio-recovery of metals. At an initial pH of 4.5, 35 degrees C temperature and 5% (w/v) pulp density, about 97% Cu, 98% Ni, 86% Co, 91% Mn and 36% Fe were dissolved in 30 days time using adapted fungus as against only 4.9% Cu, 8.2% Ni, 27% Co, 6.3% Mn and 7.1% Fe solubilized in control experiment. The results indicate that A. niger released organic acids such as oxalic and citric acids which in turn reduced the host metal oxides/hydroxides to their lower valence states, and thus dissolving the base metals following the indirect mechanism. A comparison of results obtained with chemical leaching of sea nodules using citric and oxalic acids and bio-leaching using A. niger show that the leaching of metals was more effective in presence of the fungus. The appearance of some lower oxide phases of manganese and iron in the leach residue identified by XRD phase analyses may account for unlocking of the host lattice leading to release and dissolution of metals during leaching. (C) 2010 Elsevier B.V. All rights reserved

Reductive leaching of valuable metals from indian ocean nodules by bacillus circulans

In the present investigation B. circulans, a heterotrophic microorganism has been used for the recovery of copper, nickel and cobalt from Indian Ocean nodules. The organism after reviving in growth medium and gradual adaption on sea nodules, was used for the bioleaching studies in shake flasks under a range of conditions such as pH, pulp density, particle size of nodules and temperature. The leaching of metals was found to be 92% Cu, 73% Ni, 72% Co, 38% Mn and 17% Fe in 25 days at 5% (w/v) pulp density (PD), 2 pH and 35°C. XRD identification of the leach residue showed the presence of some lower and mixed oxidation phases of manganese and some unaltered iron phases. Surface morphology of the bioleach residue was examined by SEM. The process may be accompanied by direct enzymatic action of bacteria leading to reduction of Mn (IV) to Mn (II) and Fe (III) to Fe (II) releasing the valuable metals from the host lattice for leaching in acidic conditions

Stress and safe health behaviour among mid adolescent school going children in urban Bhubaneswar, Odisha, India

Background: During adolescence, that the child is heavily influenced by his surroundings and attempts to change his or her habits and take on to newer habits. This has made relevant the emphasis of safe health behaviour in school and incorporation of stress assessment and subsequent counselling among the adolescent age group. The current study was planned among mid adolescent age group boys and girls, both from government and private schools of Bhubaneswar. Aims & Objectives: To see the association of socio-demographic characteristics with perceived stress among the adolescent children and to find the association of safe health behaviour with perceived stress among the adolescent children and determine the significant factors. Material & Methods: A total of 480 students (240 boys and girls each) selected randomly from 4 government and private schools were included in the study and administered a self-marking questionnaire which elicited information regarding safe health behaviour and also stress scores by using the Perceived Stress Scale which is a 10 points item. Results: Type of school and mother’s education emerged most significant in the sample in terms of stress experienced by the children. Children who were verbal abused by the teachers had higher stress (28.9%) compared to who were not abused (p = 0.012). In terms of health history, any report of sickness or illness in the past 3 months accounted for significantly higher stress levels (37%) compared to the group with no such history (22.5). Conclusion: These findings hint that school environment has a major role to play on the adolescent’s stress levels

Effect of mechano-chemical activation on bioleaching of Indian Ocean nodules by a fungus

The effect of mechano-chemical activation of Indian sea nodules, while recording the zeta potential, particle size distribution and surface area, on the bio-dissolution of metals by Aspergillus niger has been investigated. Activation is a term used to indicate what takes place when increasing grinding time does not result in significant change in particle size but rather results in the accumulation of energy that may lead to the development of lattice defects within the particles that can aid biological attack. It was observed that the mechano-chemical activation improved the bio-dissolution of metals such as copper, nickel and cobalt from the sea nodules at initial pH in the range 4.0–5.0. With 10 min milling of particles of 75 μm size, 86% material was reduced to 10 μm size with a change in zeta potential from −18 to −34 mV. Above 95% copper, nickel and cobalt each was leached out in 15 days time from the nodules activated for 10 min at 5% (w/v) PD and 35 °C temperature with initial pH of 4.5; the biorecovery being almost similar when the material was activated for 30 min. In the case of nodules without activation, 89% metal bioleaching was achieved in 25 days time at an initial pH of 4.5 under this condition. The mechano-chemical activation of sea nodules has thus influenced the bio-dissolution process, while providing a wider pH range available for processing of nodules with the involvement of organic acids such as oxalic and citric generated from the fungus

Highly Sensitive and Selective Rhodamine-Based “Off–On” Reversible Chemosensor for Tin (Sn⁴⁺) and Imaging in Living Cells

A structurally characterized new oxo-chromene functionalized rhodamine derivative <b>L1</b> exhibits high selectivity toward Sn⁴⁺ by forming a 1:1 complex, among other biologically important metal ions, as studied by fluorescence, absorption, and HRMS spectroscopy. Complexing with Sn⁴⁺ triggers the formation of a highly fluorescent ring-open form which is pink in color. The sensor shows extremely high fluorescence enhancement upon complexation with Sn⁴⁺, and it can be used as a “naked-eye” sensor. DFT computational studies carried out in mimicking the formation of a 1:1 complex between <b>L1</b> and Sn⁴⁺ resulted in a nearly planar pentacoordinate Sn­(IV) complex. Studies reveal that the <i>in situ</i> prepared <b>L1</b>–Sn complex is selectively and fully reversible in presence of sulfide anions. Further, confocal microscopic studies confirmed that the receptor shows <i>in vitro</i> detection of Sn⁴⁺ ions in RAW cells

Cd²⁺ Triggered the FRET “ON”: A New Molecular Switch for the Ratiometric Detection of Cd²⁺ with Live-Cell Imaging and Bound X‑ray Structure

On the basis of the Förster resonance energy transfer mechanism between rhodamine and quinoline–benzothiazole conjugated dyad, a new colorimetric as well as fluorescence ratiometric probe was synthesized for the selective detection of Cd²⁺. The complex formation of the probe with Cd²⁺ was confirmed through Cd²⁺-bound single-crystal structure. Capability of the probe as imaging agent to detect the cellular uptake of Cd²⁺ was demonstrated here using living RAW cells