[show abstract][hide abstract] ABSTRACT: Bionanotechnology has revolutionized the nano material synthesis by providing a green synthetic platform using its biological systems. Among the biological systems microalgae has tremendous potential to uptake metal ions and produce nanoparticle by detoxification process. The present study explores the intracellular and extracellular biogenic synthesis of silver nanoparticles (SNPs) using a unicellular green microalga Scenedesmus. Biosynthesized SNPs were characterized by AAS, UV-Vis spectroscopy, TEM, XRD, FTIR, DLS, TGA studies and finally checked for antibacterial activity. Intracellular nanoparticle biosynthesis is initiated by high rate of Ag(+) ion accumulation in the microalgal biomass and subsequent formation of spherical crystalline SNPS (of average size of 15-20 nm) due to biochemical reduction of Ag(+) ions. The synthesized nanoparticles were intracellular as confirmed by the UV-Vis spectra of experimental medium. Furthermore, extracellular synthesis using boiled extract shows formation of well scattered, highly stable, spherical SNPs with average size of 5-10 nm. Size and morphology of the nanoparticle was confirmed by TEM. Crystalline nature of the SNPs was evident from the diffraction peaks of XRD and bright circular ring pattern of SAED. FTIR and UV-Vis spectra showed that the biomolecules, proteins and peptides, are mainly responsible for formation and stabilization of SNPs. Further, the synthesized nanoparticles exhibited high antimicrobial activity against pathogenic gram negative and gram positive bacteria. Use of such a microalgal system provides a simple, cost effective alternative template for biosynthesis of nanomaterials in large scale system with a great use in biomedical application.
Journal of Microbiology and Biotechnology 01/2014; · 1.40 Impact Factor
[show abstract][hide abstract] ABSTRACT: A biogenic route was adopted towards the synthesis of gold nanoparticles using the extract of a novel strain, Talaromyces flavus . Reduction of chloroauric acid by the fungal extract resulted in the production of gold nanoparticle, which was further confirmed by the concordant results obtained from UV–visible spectroscopy, energy dispersive spectroscopy (EDS), and dynamic light scattering (DLS) analysis.
Morphology and the crystal nature of the synthesized nanoparticles were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD) and selected area electron diffraction (SAED). A direct correlation was observed between nanoparticle formation and the concentration of reducing
agent present in the fungal extract. The time-dependent kinetic study revealed that the bioreduction process follows an autocatalytic reaction. Crystalline, irregular, and mostly flowershaped gold nanoparticles with a mean hydrodynamic radius of 38.54±10.34 nm were obtained. pH played a significant role on
production of mono-dispersed nanoparticle. FTIR analysis partially deciphered the involvement of –NH2, −SH, and –CO groups as the probable molecules in the bio-reduction and stabilization process. Compared to the conventional methods, a time-resolved, green, and economically viable method for
floral-shaped nanoparticle synthesis was developed.
Annals of Microbiology 11/2013; · 1.55 Impact Factor
[show abstract][hide abstract] ABSTRACT: Microorganisms are a scientific asset as they remarkably orchestrate life on earth. Microorganisms play a significant role in the various cycles of terrestrial and aquatic ecosystems. Specific microbes from the ancient Precambrian age have key impact in the biogeochemical cycles of carbon and iron due to their immense metabolic versatility. They possess the unique ability to utilize a wide range of soluble electron acceptors such as nitrate, nitrite, sulphur, trimethylamine N-oxide, dimethyl sulfoxide as well as insoluble oxidized metals such as iron and manganese, various radionuclides like uranium, plutonium, etc. Of these, the dissimilatory iron reducing bacteria (DIRB) has found widespread attention due to their ability to reduce Fe (III) as sole electron acceptor coupled to the oxidation of organic carbon source (electron donor) under anerobic/facultative anaerobic conditions. This ability of DIRB was exploited in our study to extract nickel and cobalt from chromite overburden (COB). Nickel is engrained within the goethite phase of COB which restrains its release, thus rendering conventional leaching methods inefficient. A phase change of this ore to its reduced form of hematite and magnetite can loosen the matrix, enhancing the extraction efficiency. COB reduction through thermal activation by roasting at high temperatures, through reduction-magnetic separation process with activated carbon powder as the reductant , solid-state deoxidisation method utilise an energy intensive approach makes it more uneconomic and less eco-friendly. Hence, nickel extraction using microbes has gained interest in the recent past. Several studies have focused on bioleaching of COB using fungi and chemolithotrophs. These microbial processes have exhibited issues of low extraction efficiency, laborious downstream processing due to substantial fungal biomass, and tedious requirement of pH maintenance in case of chemolithotrophs.
Here, we subjected the COB to microbial reduction using DIRB followed by acid leaching for enhanced nickel-cobalt recovery. Various DIRB consortia were isolated from different marshy areas and screened the consortia capable of efficiently reducing Fe (III) of Chromite overburden (COB) under facultative anaerobic condition. DIRB was found to liberate the goethite-associated nickel as a result of the phase change in ore during its growth. The phase change was confirmed by XRD analysis, wherein the goethite and hematite peaks were observed in original COB while DIRB-treated COB showed a nickel oxide and magnetite peaks in addition to goethite and hematite. The phase change is pertained to the microbial reduction of Fe (III) to Fe (II). Morphological study using FESEM showed a variance from needle shaped goethite in original ore to granular magnetite in treated ore. About 27% nickel was obtained on bio-reduction of COB which was enhanced by 43% on treating with 8M sulphuric acid, resulting in 70% Ni recovery.
INTERNATIONAL CONFERENCE ON CONSERVING BIODIVERSITY FOR SUSTAINABLE DEVELOPMENT((INCCBSD 2013), NATIONAL INSTITUTE OF TECHNOLOGY,Rourkela; 08/2013
[show abstract][hide abstract] ABSTRACT: Biosurfactants are amphiphilic molecules having hydrophobic and hydrophilic moieties produced by various microorganisms. These molecules trigger the reduction of surface tension or interfacial tension in liquids. A biosurfactant-producing halophile was isolated from Lake Chilika, a brackish water lake of Odisha, India (19°41′39″N, 85°18′24″E). The halophile was identified as Bacillus tequilensis CH by biochemical tests and 16S rRNA gene sequencing and assigned accession no. KC851857 by GenBank. The biosurfactant produced by B. tequilensis CH was partially characterized as a lipopeptide using thin-layer chromatography, Fourier transform infrared spectroscopy, and nuclear magnetic resonance techniques. The minimum effective concentration of a biosurfactant for inhibition of pathogenic biofilm (Escherichia coli and Streptococcus mutans) on hydrophilic and hydrophobic surfaces was found to be 50 μg ml−1. This finding has potential for a variety of applications.
Applied Biochemistry and Biotechnology 08/2013; · 1.89 Impact Factor
[show abstract][hide abstract] ABSTRACT: The effect of an adapted Dissimilatory Iron Reducing bacterial consortium (DIRB) towards bio-reduction of Sukinda Chromite overburden (COB) with enhanced recovery of nickel and cobalt is being reported for the first time. The remarkable ability of DIRB to utilize Fe (III) as terminal electron acceptor reducing it to Fe (II) proved beneficial for treatment of COB as compared to previous reports for nickel leaching. XRD studies showed goethite as the major iron-bearing phase in COB. Under facultative anaerobic conditions, goethite was reduced to hematite and magnetite with the exposure of nickel oxide. FESEM studies showed DIRB to be associated with COB through biofilm formation with secondary mineral precipitates of magnetite deposited as tiny globular clusters on the extra polymeric substances. The morphological and mineralogical changes in COB, post DIRB application, yielded a maximum of 68.5% Nickel and 80.98% Cobalt in 10 days using 8M H2SO4.
[show abstract][hide abstract] ABSTRACT: Acetyl-CoA carboxylase (ACCase), a biotin-dependent enzyme that catalyses the first committed step of fatty acid biosynthesis, is considered as a potential target for improving lipid accumulation in oleaginous feedstocks, including microalgae. ACCase is composed of three distinct conserved domains, and understanding the structural details of each catalytic domain assumes great significance to gain insights into the molecular basis of the complex formation and mechanism of biotin transport. In the absence of a crystal structure for any single heteromeric ACCase till date, here we report the first heteromeric association model of ACCase from an oleaginous green microalga, Chlorella variabilis, using a combination of homology modelling, docking and molecular dynamic simulations. The binding site of the docked biotin carboxylase (BC) and carboxyltransferase (CT) were predicted to be contiguous but distinct in biotin carboxyl carrier protein (BCCP) molecule. Simulation studies revealed considerable flexibility for the BC and CT domains in the BCCP-bound forms, thus indicating the adaptive behaviour of BCCP. Further, principal component analysis revealed that in the presence of BCCP, the BC and CT domains exhibited an open-state conformation via the outward clockwise rotation of the binding helices. These conformational changes might be responsible for binding of BCCP domain and its translocation to the respective active sites. Various rearrangements of inter-domain hydrogen bonds (H-bonds) contributed to conformational changes in the structures. H-bond interactions between the interacting residue pairs involving Glu201BCCP/Arg255BC and Asp224BCCP/Gln228CT were found to be essential for the intermolecular assembly. The present findings are consistent with previous biochemical studies.
Applied biochemistry and biotechnology 05/2013; · 1.94 Impact Factor
[show abstract][hide abstract] ABSTRACT: Optimization studies of plasma smelting of red mud were carried out. Reduction of the dried red mud fines was done in an extended arc plasma reactor to recover the pig iron. Lime grit and low ash metallurgical (LAM) coke were used as the flux and reductant, respectively. 2-level factorial design was used to study the influence of all parameters on the responses. Response surface modeling was done with the data obtained from statistically designed experiments. Metal recovery at optimum parameters was found to be 79.52%.
Plasma Science and Technology 05/2013; 15(5):459. · 0.51 Impact Factor
[show abstract][hide abstract] ABSTRACT: Acetyl-CoA carboxylase (ACCase), a biotin-dependent enzyme that catalyzes the first
committed step of fatty acid biosynthesis is considered as a potential target for
improving lipid accumulation in oleaginous feedstocks, including microalgae. ACCase
is composed of three distinct conserved domains and understanding the structural
details of each catalytic domain assumes great significance to gain insights into the
molecular basis of the complex formation and mechanism of biotin transport. In the
absence of a crystal structure for any single heteromeric ACCase till date, here we
report the first heteromeric association model of ACCase from an oleaginous green
microalga, Chlorella variabilis using a combination of homology modeling, docking and
molecular dynamic simulations. The binding site of the docked biotin carboxylase (BC)
and carboxyltransferase (CT) were predicted to be contiguous but distinct in biotin
carboxyl carrier protein (BCCP) molecule. Simulation studies revealed considerable
flexibility for the BC and CT domains in the BCCP bound forms, thus indicating the
adaptive behaviour of BCCP. Further, principal component analysis revealed that in
presence of BCCP, the BC and CT domains exhibited an open-state conformation via
the outward clockwise rotation of the binding helices. These conformational changes
might be responsible for binding of BCCP domain and its translocation to the
respective active sites. Various rearrangements of inter-domain hydrogen bonds (Hbonds)
contributed to conformational changes in the structures. H-bond interactions
between the interacting residue pairs involving Glu201BCCP/Arg255BC and
Asp224BCCP/Gln228CT were found to be essential for the intermolecular assembly.
The present findings are consistent with previous biochemical studies.
Applied Biochemistry and Biotechnology 01/2013; Article in Press. · 1.89 Impact Factor
[show abstract][hide abstract] ABSTRACT: This paper presents the application of the Taguchi experimental design in developing nanostructured yittria stabilized zirconia (YSZ) coatings by plasma spraying process. This paper depicts dependence of adhesion strength of as-sprayed nanostructured YSZ coatings on various process parameters, and effect of those process parameters on performance output has been studied using Taguchi's L16 orthogonal array design. Particle velocities prior to impacting the substrate, stand-off-distance, and particle temperature are found to be the most significant parameter affecting the bond strength. To achieve retention of nanostructure, molten state of nanoagglomerates (temperature and velocity) has been monitored using particle diagnostics tool. Maximum adhesion strength of 40.56 MPa has been experimentally found out by selecting optimum levels of selected factors. The enhanced bond strength of nano-YSZ coating may be attributed to higher interfacial toughness due to cracks being interrupted by adherent nanozones.
The Scientific World Journal 01/2013; 2013:527491. · 1.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: Abstract Bioleaching of a low grade chalcopyrite (ball
mill spillage material) was tested for copper recovery in
shake ﬂasks. The original samples (as received) were
thermally activated (600°C, 30 min) to notice the change in
physico-chemical and mineralogical characteristics of the
host rock and subsequently its effect on copper recovery. A
mixed culture of acidophilic chemolithotrophic bacterial
consortium predominantly entailing Acidithiobacillus fer-
rooxidans strain was used for bioleaching studies and
optimization of process parameters of both original and
thermally activated samples. Mineralogical characteriza-
tion studies indicated the presence of chalcopyrite, pyrite
in the silicate matrix of the granitic rock. Field emission
scanning electron microscopy coupled with Energy
dispersive spectroscopy (FESEM-EDS) and X-ray Fluor-
escence (XRF) analysis indicated mostly SiO2. With pH 2,
pulp density 10% w/v, inoculum 10% v/v, temperature
30°C, 150 r$min–1
,49% copper could be recovered in 30
days from the ﬁnest particle size ( – 1 + 0.75 mm) of the
original spillage sample. Under similar conditions 95%
copper could be recovered from the thermally activated
sample with the same size fraction in 10 days. The study
revealed that thermal activation leads to volume expansion
in the rock with the development of cracks, micro and
macro pores on its surface, thereby enabling bacterial
solution to penetrate more easily into the body, facilitating
enhanced copper dissolution.
Keywords ball mill spillage, thermal activation, bioleach-
Frontiers of Environmental Science & Engineering in China(Impact Factor-0.75). 01/2013; 7(2):281–293.
[show abstract][hide abstract] ABSTRACT: The concept of using microalgae as an alternative renewable source of biofuel has gained much importance in recent years. However, its commercial feasibility is still an area of concern for researchers. Unraveling the fatty acid metabolic pathway and understanding structural features of various key enzymes regulating the process will provide valuable insights to target microalgae for augmented oil content. FabH (β-ketoacyl-acyl carrier protein synthase; KAS III) is a condensing enzyme catalyzing the initial elongation step of type II fatty acid biosynthetic process and acyl carrier protein (ACP) facilitates the shuttling of the fatty acyl intermediates to the active site of the respective enzymes in the pathway. In the present study, a reliable three-dimensional structure of FabH from Chlorella variabilis, an oleaginous green microalga was modeled and subsequently the key residues involved in substrate binding were determined by employing protein-protein docking and molecular dynamics (MD) simulation protocols. The FabH-ACP complex having the lowest docking energy score showed the binding of ACP to the electropositive FabH surface with strong hydrogen bond interactions. The MD simulation results indicated that the substrate-complexed FabH adopted a more stable conformation than the free enzyme. Further, the FabH structure retained its stability throughout the simulation although noticeable displacements were observed in the loop regions. Molecular simulation studies suggested the importance of crucial hydrogen bonding of the conserved Arg(91) of FabH with Glu(53) and Asp(56) of ACP for exhibiting high affinity between the enzyme and substrate. The molecular modeling results are consistent with available experimental results on the flexibility of FabH and the present study provides first in silico insights into the structural and dynamical aspect of catalytic mechanism of FabH, which could be used for further site-specific mutagenic experiments to develop engineered high oil-yielding microalgal strains for biofuel production.
[show abstract][hide abstract] ABSTRACT: Optimizing microalgal biofuel production using metabolic engineering tools requires an in-depth understanding of the structure-function relationship of genes involved in lipid biosynthetic pathway. In the present study, genome-wide identification and characterization of 398 putative genes involved in lipid biosynthesis in Arabidopsis thaliana Chlamydomonas reinhardtii, Volvox carteri, Ostreococcus lucimarinus, Ostreococcus tauri and Cyanidioschyzon merolae was undertaken on the basis of their conserved motif/domain organization and phylogenetic profile. The results indicated that the core lipid metabolic pathways in all the species are carried out by a comparable number of orthologous proteins. Although the fundamental gene organizations were observed to be invariantly conserved between microalgae and Arabidopsis genome, with increased order of genome complexity there seems to be an association with more number of genes involved in triacylglycerol (TAG) biosynthesis and catabolism. Further, phylogenomic analysis of the genes provided insights into the molecular evolution of lipid biosynthetic pathway in microalgae and confirm the close evolutionary proximity between the Streptophyte and Chlorophyte lineages. Together, these studies will improve our understanding of the global lipid metabolic pathway and contribute to the engineering of regulatory networks of algal strains for higher accumulation of oil.
[show abstract][hide abstract] ABSTRACT: Tumbling mills emit vibration that can be captured to assess its performance. We interpret the vibration signature of a one meter diameter mill in response to changes in mill speed, rock/particle size, quantity of balls, and slurry viscosity. A ±500g tri-axial accelerometer with a wireless transmitter located on the surface of the mill shell transmits vibration signal to a receiver connected to a PC. The quality of the vibration signal is preserved due to the use of wireless transfer of data. The filtered vibration signal in the frequency domain is averaged which is then used as a parameter for comparison purpose. This approach to signal analysis is most suitable to compare vibration response of a mill to changes in operating parameters. The mill shell vibration signature turned out to be an excellent indicator to establish the differences in mill performance under wet versus dry grinding conditions, coarse versus fine grinding, changes in mill speed, ball load, etc. The broader implication of the main observations in the context of development of a diagnostic tool to assess the mill performance is highlighted.
[show abstract][hide abstract] ABSTRACT: Silicon carbide dendrite (micrometer size) is produced by carbothermic reduction of rice husk ash in an arc plasma. Transmission electron microscopy reveals the occurrence of equispaced primary arms (60–70 nm in length) in the dendrite consisting of nanorod bundles. Each nanorod is seen to contain thin transverse lamellas, which appear like slip bands/twins in atomic layer thickness. A liquid phase Si-based growth mechanism is discussed to understand the dendrite growth.
Journal of the American Ceramic Society 09/2010; 93(10):3080 - 3083. · 2.11 Impact Factor
[show abstract][hide abstract] ABSTRACT: A one-pot novel facile synthesis of a high surface area nanoakaganeite (β-FeOOH) involving formation of a chelate as the precursor has been described. Ferric chloride solution mixed with ethylenediaminetetraacetic acid (EDTA) solution was heated to 90 °C followed by neutralization with ammonia to obtain a pH of 9, and the precipitate was stirred for half an hour. The precipitate was filtered, washed, and dried at 90 °C. Chemical, X-ray diffraction (XRD), Fourier transform infrared (FTIR), and Raman analyses confirmed the sample to be akaganeite. Transmission electron microscopy (TEM) studies showed the formation of monophase cigar-shaped akaganeite nanorods of (15 to 20) nm in width and (80 to 100) nm in length. The surface area obtained by the Brunauer−Emmett−Teller (BET) method was 176.16 m2·g−1. The nanopowder so obtained was used to generate sorption data for the removal of Pb(II), Cd(II), Cu(II), and Co(II) from aqueous solutions. The relative importance of experimental parameters such as solution pH, contact time, temperature, and concentration of adsorbate on the uptake of various cations was evaluated. The sorption kinetics followed a pseudosecond-order model. Both Langmuir and Freundlich models fitted the isothermic data of all of the cations well. High Langmuir monolayer capacities of (163.9, 70.4, 80, and 98) mg·g−1 were obtained for Pb(II), Cd(II), Co(II), and Cu(II), respectively. The XRD patterns of Pb(II)-, Co(II)-, and Cu(II)-loaded samples showed positive shifts in d-values for the three main planes, that is, (110), (200), and (311) of akaganeite, while Cd(II)-loaded sample showed a negative shift in d-values of the (110) and (400) planes, indicating a disturbance in the internal structure during sorption.
Journal of Chemical and Engineering Data - J CHEM ENG DATA. 03/2010; 55(4).
[show abstract][hide abstract] ABSTRACT: We investigate the electrode reactions involved in the electrolytic precipitation of nickel hydroxide from nickel nitrate through quantitative assessment of the reaction products using stainless steel cathode with Ti and Ni anodes. The nitrate ion is reduced at the cathode to form nitrite and ammonium ion, the later being the major product. The production of ammonium ion followed either directly via reduction of nitrate to ammonium ion or in steps via nitrate reduction to nitrite which further reduced to ammonium ion. Finally, we report XRD measurements, tap density, and the discharge capacity performed on the electrolytically precipitated Ni(OH)2.