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.

Summary

In the present investigation fractioned cellular components like intact pigment bearing thylakoids/chloroplasts, carotenoids, protein, polysaccharides were extracted from the cyanobacterium Anabaena sphaerica and green alga Chlorococcum infusionum. Each of these extracts was used separately in search for efficient reducing agents during gold nanoparticle (GNP) production in pro- and eukaryotic algal cell systems. The whole biomass and extracted compounds or cellular structures were exposed in 25 mg L−1 aqueous hydrogen tetrachloroaurate solutions separately at room temperature. Isolated viable chloroplasts from C. infusionum and thylakoids from A. sphaerica were found to be able to reduce gold ions. The protein extracts of both strains were also able to synthesize GNP at 4°C. Extracted polysaccharides of the two strains responded differently. Polysaccharides from A. sphaerica showed positive response in GNP synthesis, whereas no change was observed for C. infusionum. The carotenoids extracts from both strains acted like an efficient reducing agent. Initially the reducing efficiency of these extracted components was confirmed by the appearance of purple color in biomass or in experimental media. The GNPs, synthesized within the biomass were extracted by sonication with sodium citrate. The UV–vis spectroscopy of extracted purple colored suspensions and media showed the absorption bands at approximately 530–540 nm indicating a strong positive signal of GNP synthesis. Transmission electro n microscopy determined the size and shapes of the particles. The X-ray diffraction study of the synthesized GNP revealed that the 2θ values appeared at 38.2°, 44.5°, 64.8° and 77.8°. Amongst all, isolated thylakoids and chloroplast showed only spherical GNP production with variable size range at pH 4. Monodisperse GNPs were also synthesized by isolated thylakoids and chloroplast at pH 9. A detailed morphological change of gold treated biomass was revealed employing scanning electron microscopy. The fluorescent property of gold loaded cells was studied by fluorescence microscopy.

Biogenic synthesis of gold nanoparticle using fractioned cellular components from eukaryotic algae and cyanobacteria

Rice grain arsenic and nutritional content during post harvesting to cooking: A review on arsenic bioavailability and bioaccessibility in humans.

Microencapsulation of antioxidant-rich fraction obtained by supercritical carbon dioxide extraction (at 50°C, 500 bar with extraction time of 90 min, and flow rate of CO2 at 2 L/min) of lyophilized biomass of Phormidium valderianum was carried out in a spray dryer using maltodextrin and gum arabic. Microencapsulation conditions that provided the best combination of phytochemical properties such as antioxidant activity, phenolic content, and reducing power with reasonable powder yield were an inlet temperature of 130°C and wall material composition as maltodextrin: gum arabic = 70 : 30. Toxicological study reported that the Anatoxin-a content of this encapsulated powder was below the limit of detection of HPLC. Storage study established that encapsulation of this antioxidant-rich algal extract resulted in eight times enhancement of half-life () values. The release profile of microencapsulated antioxidant-rich fraction from the encapsulated powder was found to follow first order anomalous transport kinetics. Therefore, this microencapsulated algal extract with minimum toxicity is a source of natural antioxidant and could have promising use as novel dietary supplement.

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Spray Dried Extract of Phormidium valderianum as a Promising Source of Natural Antioxidant

Phormidium tenue (Meneghini) Gomont , a microscopic filamentous cyanobacterium was exposed to 5ppm Na-arsenate (sub lethal dose) for different time intervals (1h, 3h and 24h) at a pH variation of 5.5, 7.0 and 8.5 to study the accumulation pattern of toxic metalloid arsenic. It was observed that arsenic accumulation of P. tenue increased with time and maximum accumulation was recorded in pH-7 after 24h exposure (80.51 mg. g 1 ). In another experiment P. tenue was treated with different concentrations of Sodium arsenate (0.1, 1, 5, 10, 25, 50 and 100ppm) in pH-7 to study the growth pattern and changes in biochemical parameters like, chlorophyll a , carotenoids, phycobiliproteins, total protein and carbohydrate content in control and arsenic exposed biomass. This study was done to assess primarily the ability of the cyanobacteria for arsenic removal and to study the cellular biochemistry of arsenic exposed biomass for a longer period of time. From the study it was evident that P. tenue responded differently in different doses of arsenic and showed optimum growth even when exposed to 50ppm arsenic for 60 days indicating arsenic resistance.

Scope of phycoremediation of Arsenic using Phormidium tenue with special reference to modulation in cellular biochemistry

The taxonomic study of marine seaweeds from Indian Sundarbans mangrove forest reveals the presence of nine taxa belonging to the class Chlorophyceae and Rhodophyceae. The present paper deals the morphotaxonomic description of nine taxa of which two from Chlorophyceae and seven from Rhodophyceae were recorded. Among the Chlorophyceae two species of Ulva viz. U. lactuca and U. intestinalis were found. The Rhodophycean taxa belongs to Catenella with two species viz. C. repens and C. nipae, Polysiphonia, Bostrychia, Compsopogon, Gelidium and Ceramium. The temperature (oC), pH and salinity were also studied at the time of collection of seaweeds.

Ruma Pal

Papers

Biogenic synthesis of gold nanoparticle using fractioned cellular components from eukaryotic algae and cyanobacteria

Rice grain arsenic and nutritional content during post harvesting to cooking: A review on arsenic bioavailability and bioaccessibility in humans.

Spray Dried Extract of Phormidium valderianum as a Promising Source of Natural Antioxidant

Scope of phycoremediation of Arsenic using Phormidium tenue with special reference to modulation in cellular biochemistry

Morphotaxonomic account of some common seaweeds from Indian Sundarbans mangrove forest and inner island area