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.

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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.

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

Microalgal biotechnology has gained considerable importance in recent decades and its use is extending day by day into several areas like nutraceutical research, renewable energy source, production of essential biomolecules like β-carotene, astaxanthin, PUFA, bio colorant production, wastewater treatment, bioremediation and aquaculture etc. Among all these, microalgae as a source of nutrition have drawn the attention since long back and are widely used in animal nutrition. Fishmeal is the preferred protein ingredient of feed in aquaculture industry, contributing significantly to the variable production cost. However, decreasing fishmeal supply and increasing costs threaten the sustainability and growth of the aquaculture industry. Therefore, complete or partial substitution of fishmeal with alternative proteins is needed to solve the problem. Presently, microalgae are used worldwide as an alternate protein source replacing fishmeal successfully. In feeding trials with fish, many types of microalgae have been found to be used for increasing growth (protein accretion), feed utilization, physiological activity, stress response, starvation tolerance, disease resistance, and carcass quality. In the present communication an attempt has been taken to review the application of different microalgae in rearing of aquaculture animal especially the fishes.

Microalgae in Aquaculture: A Review with Special References to Nutritional Value and Fish Dietetics

Pro- and eukaryotic algal genera, i.e. Lyngbya majuscula, Spirulina subsalsa (Cyanophyceae) and Rhizoclonium hieroglyphicum (Chlorophyceae), were used for bio-recovery of gold (Au) out of aqueous solution. Au (III) spiked with 198Au was used for the experiment. Batch laboratory experiments indicated quick metabolic independent binding of Au to the algae followed by active accumulation and subsequent reduction. Gold accumulation by different algal genera was found in order of R. hieroglyphicum > L. majuscula > S. subsalsa (3.28, 1.93 and 1.73 mg g-1, respectively). It was observed that the algal biomass and the media used for the experiment turned purple in colour indicating reduction of Au (III) to Au (0) at intra- and extracellular level. This was confirmed by TEM studies of L. majuscula biomass exposed in HAuCl4 solution where <20-nm-sized gold particles were found both inside as well as on the surface of the cell. Up to 90–100% of accumulated gold was recovered from the algal biomass by using nitric acid and acidic thiourea solution.

Biorecovery of gold using cyanobacteria and an eukaryotic alga with special reference to nanogold formation – a novel phenomenon

The cyanobacteria Phormidium valderianum, P. tenue and Microcoleus chthonoplastes and the green algae Rhizoclonium fontinale, Ulva intestinalis, Chara zeylanica and Pithophora oedogoniana were exposed to hydrogen tetrachloroaurate solution and were screened for their suitability for producing nano‐gold. All three cyanobacteria genera and two of the green algae (Rhizoclonium fontinale and Ulva intestinalis) produced gold nanoparticles intracellularly, confirmed by purple colouration of the thallus within 72 h of treatment at 20°C. Extracted nanoparticle solutions were examined by UV‐vis spectroscopy, transmission electron microscopy (TEM) and X‐ray diffractometry (XRD). XRD confirmed the reduction of Au (III) to Au (0). UV‐vis spectroscopy and TEM studies indicated the production of nanoparticles having different shapes and sizes. Phormidium valderianum synthesized mostly spherical nanoparticles, along with hexagonal and triangular nanoparticles, at basic and neutral pHs (pH 9 and pH 7, respectively). Medi...

Screening of different algae for green synthesis of gold nanoparticles

Intracellular bioconversion of auric ion (Au3+) to gold nanorod (Au0) by the cyanobacterium Nostoc ellipsosporum has been observed for the first time in laboratory condition. The nanorods were produced within the cell after exposing the healthy growing filaments to 15 mg L−1 gold (III) solution (pH 4.5) for 48 h at 20°C. The gold nanoparticles were extracted with sodium citrate solution and were subjected to UV–Visible spectroscopy. The characteristic surface-multiple plasmon bands at 560, 610, and 670 nm were observed. The nature and size of the particles were determined by transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), and zeta potential studies. The nanorod size ranged from 137 to 209 nm in length and 33 to 69 nm in diameter. DLS study revealed the average hydrodynamic size as 435 nm and XRD study indicated the reduction of Au3+ to Au0. Methods of extraction and preservation of gold nanorod particles have also been studied.

Gold nanorod production by cyanobacteria—a green chemistry approach

Algal biomass can serve as rich source of bioproducts including lipids for diverse commercial applications. Both biomass production and lipid accumulation are limited by several factors, of which nutrients play a vital role. In the present investigation, the nutritional requirement for the growth by a (an autotrophic) Chlorococcum infusionum was determined using a Plackett–Burman based statistical screening experiment. Five out of the fifteen factors of a reported production medium were found to be significantly affecting the biomass growth. The components NaNO3, K2HPO4, FeSO4.7H2O and KOH had direct proportional correlation with biomass production, while MgSO4 showed inverse proportional relationship in the selected experimental range. Nitrogen was the most influential factor with an effect contribution of 45.77% and a very low p-value of

Ruma Pal

Papers

Microalgae in Aquaculture: A Review with Special References to Nutritional Value and Fish Dietetics

Biorecovery of gold using cyanobacteria and an eukaryotic alga with special reference to nanogold formation – a novel phenomenon

Screening of different algae for green synthesis of gold nanoparticles

Gold nanorod production by cyanobacteria—a green chemistry approach

Strategic enhancement of algal biomass and lipid in Chlorococcum infusionum as bioenergy feedstock