Biosorbents for heavy metals removal and their future

Silver nanoparticles (NPs) have been the subjects of researchers because of their unique properties (e.g., size and shape depending optical, antimicrobial, and electrical properties). A variety of preparation techniques have been reported for the synthesis of silver NPs; notable examples include, laser ablation, gamma irradiation, electron irradiation, chemical reduction, photochemical methods, microwave processing, and biological synthetic methods. This review presents an overview of silver nanoparticle preparation by physical, chemical, and biological synthesis. The aim of this review article is, therefore, to reflect on the current state and future prospects, especially the potentials and limitations of the above mentioned techniques for industries.

/pdf/synthesis-of-silver-nanoparticles-chemical-physical-and-2arg54gdmv.pdf

Synthesis of silver nanoparticles: chemical, physical and biological methods.

http://fac.ksu.edu.sa/sites/default/files/Abdel-Raouf%20et%20al%2C2012.pdf

Microalgae and wastewater treatment.

Biogenic synthesis of nanoparticles: A review

Using aqueous cyanobacterial extracts in the synthesis of silver nanoparticle is looked as green, ecofriendly, low priced biotechnology that gives advancement over both chemical and physical methods. In the current study, an aqueous extract of Oscillatoria limnetica fresh biomass was used for the green synthesis of Ag-NPs, since O. limnetica extract plays a dual part in both reducing and stabilizing Oscillatoria-silver nanoparticles (O-AgNPs). The UV-Visible absorption spectrum, Fourier transforms infrared (FT-IR), transmission electron microscopy (TEM) and scanning electron microscope (SEM) were achieved for confirming and characterizing the biosynthesized O-AgNPs. TEM images detected the quasi-spherical Ag-NPs shape with diverse size ranged within 3.30–17.97 nm. FT-IR analysis demonstrated the presence of free amino groups in addition to sulfur containing amino acid derivatives acting as stabilizing agents as well as the presence of either sulfur or phosphorus functional groups which possibly attaches silver. In this study, synthesized Ag-NPs exhibited strong antibacterial activity against multidrug-resistant bacteria (Escherichia coli and Bacillus cereus) as well as cytotoxic effects against both human breast (MCF-7) cell line giving IC50 (6.147 µg/ml) and human colon cancer (HCT-116) cell line giving IC50 (5.369 µg/ml). Hemolytic activity of Ag-NPs was investigated and confirmed as being non- toxic to human RBCs in low concentrations.

/pdf/synthesis-and-biological-characterization-of-silver-1gpnjonquc.pdf

Synthesis and biological characterization of silver nanoparticles derived from the cyanobacterium Oscillatoria limnetica.

The co-cultivation approach using cyanobacteria—Leptolyngbya tenuis and green alga—Chlorella ellipsoidea demonstrated in the present study showed additive and synergistic effects on biomass yield, biomass productivity, lipid yield, lipid productivity, CO2 fixation, and cadmium bioremediation efficiency. The results of co-culture in batch mode revealed about 2–3 times increase in biomass and two times increase in total lipid, when compared to the pure culture batches. The results revealed that co-cultures exhibited significantly high CO2 fixation rate of 2.63  ±  0.09 g/L/d, which is 1.5–2 times better than monocultures (P   Chlorella (58%, 0.29 mg/L) > Leptolyngbya (50%, 0.25 mg/L) (P < 0.05). In addition, fatty acid composition, CHNS analysis, biodiesel characterization, and biochemical compositions were also determined using co-culture method. The maximum biomass yield, productivity, lipid content, and CO2 fixation rate in cadmium induced co-culture were 3.95  ±  0.13 g/L, 258.88  ±  15.75 mg/L/d, 41.43  ±  0.71%, and 3.21  ±  0.20 g/L/d, respectively which is 1.2, 1.3, 2.3, and 1.2 times higher than the control (P < 0.05). Cadmium induced changes in growth and lipid yield using co-culture suggests cost-effective and eco-friendly production of biodiesel and carbon mitigation.

Co-Cultivation of Leptolyngbya tenuis (Cyanobacteria) and Chlorella ellipsoidea (Green alga) for Biodiesel Production, Carbon Sequestration, and Cadmium Accumulation

The bio-sorption of heavy and toxic radionuclides by three genera of algae from different taxonomic groups was studied employing the recently developed 'Tracer Packet' technique. The ‘tracer packet’ of heavy and toxic metals' contained 197Hg, 198,199,200,201Tl, 199,200,201Pb, 204Bi and 204,205Po radionuclides in carrier-free state and was produced by irradiating a gold metal foil with medium energy 7Li and 12C beams successively in a 12 MV Pelletron. Three genera, Spirulina from Cyanophyceae, Oedogonium from Chlorophyceae and Catenella from Rhodophyceae were cultured in laboratory condition and were used in the experiment. The radionuclide accumulation varied according to different genera at different pH levels. At basic pH Spirulina showed a maximum radionuclide accumulation in comparison to other genera.

Application of tracer packet technique to the study of the bio-sorption of heavy and toxic metal radionuclides by algae

Antioxidant properties of four common green algal genera viz. Cladophora glomerata, Chaetomorpha aerea, Rhizoclonium crassipellitum, and Pithophora cleveana collected from Sunderban areas of Eastern India were tested in controlled and nutrient stress conditions. Experimental algae were exposed to growth media with variations in nitrate and NaCl salt concentrations from 0 to 1500 ppm level for a period of 21 days. A dose-dependent upregulation in total phenols, flavonoids, pigment, and antioxidant property in relation to % DPPH activity and % ferrous ion chelating activity was observed. Maximum phenol content was observed for algal biomass exposed to 1500 ppm nitrate stress conditions (52.55 ± 0.01 mg GAE/g DW-16.48 ± 0.041 mg GAE/g DW) with Rhizoclonium showing the maximum contents. In the case of total flavonoid content, maximum upregulation was noted in the hypersaline conditions and Pithophora showed the highest contents amongst all (71.8 ± 0.21 mg QE/g DW). The highest carotenoid contents were observed in 750 ppm stress condition. Optimally stressed algal biomass having maximum carotenoid levels and high antioxidant levels were selected as fish feed ingredients, based on dose- and time-dependent two-way Anova and Tukeys test (750 ppm nitrate, 7 days). The processed biomass was included as fish feed ingredient to study the nutritive effects on goldfish (Carassius auratus). Algal feed (AF) was prepared from algal biomass only, which was further mixed with the commercial feed (CF) in varying proportions to formulate three different types of value-added feed (VAF). The experimental feed (25% VAF, 50% VAF, 75%VAF and AF) were tested against commercial feed (control) for 30 days in artificially aerated static aquaria system. The feed type formulated as 50% VAF was found to be most effective in terms of skin pigmentation, growth, and antioxidant activities of experimental fishes showing almost (1.44–4-folds increase) compared to the control setup. Statistically significant results were obtained regarding nutritive properties of experimental feed and fishes using PCA and Tukeys test respectively. Body weight gain and specific growth rate also changed significantly in experimental fishes.

Investigation on the effects of nitrate and salinity stress on the antioxidant properties of green algae with special reference to the use of processed biomass as potent fish feed ingredient

We report an eco-friendly method for biosynthesis of gold-silica (Au-SiO2) nanocomposite using a diatom, Amphora copulata, as reducing agent. The live cells of Amphora covered by siliceous frustules reacted with hydrogen tetra-auro chlorate (HAuCl4), and Au-SiO2 particles were synthesized after 72 h of reaction. Energy-dispersive X-ray (EDAX) analysis confirmed the presence of Au and SiO2 nanoparticles in a composite form, and their characterization was done by UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), and scanning (SEM) and transmission (TEM) electron microscopy. The SEM study revealed that composite particles were deposited on the siliceous frustules of live cells, whereas in dead diatom cells, the surface remained unchanged. The TEM analysis confirmed the synthesis of triangular-, spherical-, and hexagonal-shaped Au-SiO2 particles with 5 to 45-nm size range. Biogenic Au-SiO2 nanoparticles were tested for DNA binding affinity by agarose gel electrophoresis and TEM study after 30 min of interaction with isolated DNA from the green alga, Pithophora. The synthesized nanoparticles were found to bind with DNA molecules without any surface modification. The TEM images of Au-SiO2 particles, taken after interaction with DNA, showed the arrangement of particles in specific manner which formed a “Y”-shaped, chain-like, and coiling structure, indicating that the diatom-based bio-synthesized Au-SiO2 particles were very efficient in binding with DNA which could be applied in the bio-medical field directly.

Diatom-based biosynthesis of gold-silica nanocomposite and their DNA binding affinity

Six Cyanobacterial and fifteen other algal taxa from Sundarban mangrove forest of South East Asia have been analyzed for total lipid estimation and fatty acid profiling to search for a suitable feedstock for algal biodiesel production. Total lipid content varied from 7 – 23 % for the studied genera. GCMS analysis revealed that Palmitic (16:0) and Oleic (18:1) as major fatty acids from the taxa collected from freshwater, brackish water and marine habitat of Sundarban with variable salinity (0-23psu). A few microalgae from cyanophyceae like, Lyngbya majuscula, Phormidium valderianum, Synechocystis pevalekii and chlorophycean genera viz. Rhizoclonium riparium, Rhizoclonium africanum, Pithophora cleveana, Spirogyra orientalis and Cladophora crystallina, having suitable fatty acid composition were identified for biodiesel production. Fatty acid profile showed more diversification in unsaturated fatty acid in fresh water region, indicating more variable environment in upstream fresh water regions of Sundarban.

Ruma Pal

Papers

Co-Cultivation of Leptolyngbya tenuis (Cyanobacteria) and Chlorella ellipsoidea (Green alga) for Biodiesel Production, Carbon Sequestration, and Cadmium Accumulation

Application of tracer packet technique to the study of the bio-sorption of heavy and toxic metal radionuclides by algae

Investigation on the effects of nitrate and salinity stress on the antioxidant properties of green algae with special reference to the use of processed biomass as potent fish feed ingredient

Diatom-based biosynthesis of gold-silica nanocomposite and their DNA binding affinity

Mapping Algae of Sundarban Origin as Lipid Feedstock for Potential Biodiesel Application