The ungenerous release of metals from different industrial, agricultural, and anthropogenic sources has resulted in heavy metal pollution. Metals with a density larger than 5 g cm−3 have been termed as heavy metals and have been stated to be potentially toxic to human and animals. Algae are known to be pioneer organisms with the potential to grow under extreme conditions including heavy metal-polluted sites. They have evolved efficient defense strategies to combat the toxic effects exerted by heavy metal ions. Most of the algal strains are reported to accumulate elevated metal ion concentration in cellular organelles. With respect to that, this review focuses on understanding the various strategies used by algal system for heavy metal resistance. Additionally, the application of this metal resistance in biosynthesis of metal nanoparticles and metal oxide nanoparticles has been investigated in details. We thereby conclude that algae serve as an excellent system for understanding metal uptake and accumulation. This thereby assists in the design and development of low-cost approaches for large-scale synthesis of nanoparticles and bioremediation approach, providing ample opportunities for future work.

Heavy metal resistance in algae and its application for metal nanoparticle synthesis

Surface characterization and metal ion adsorption properties of Spirulina sp. and Spirulina maxima were verified by various instrumental techniques. FTIR spectroscopy and potentiometric titration were used for qualitative and quantitative determination of metal ion-binding groups. Comparative FTIR spectra of natural and Cu(II)-treated biomass proved involvement of both phosphoryl and sulfone groups in metal ions sorption. The potentiometric titration data analysis provided the best fit with the model assuming the presence of three types of surface functional groups and the carboxyl group as the major binding site. The mechanism of metal ions biosorption was investigated by comparing the results from multielemental analyses by ICP-OES and SEM-EDX. Biosorption of Cu(II), Mn(II), Zn(II), and Co(II) ions by lyophilized Spirulina sp. was performed to determine the metal affinity relationships for single- and multicomponent systems. Obtained results showed the replacement of naturally bound ions: Na(I), K(I), or Ca(II) with sorbed metal ions in a descending order of Mn(II) > Cu(II) > Zn(II) > Co(II) for single- and Cu(II) > Mn(II) > Co(II) > Zn(II) for multicomponent systems, respectively. Surface elemental composition of natural and metal-loaded material was determined both by ICP-OES and SEM-EDX analysis, showing relatively high value of correlation coefficient between the concentration of Na(I) ions in algal biomass.

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Biosorption of microelements by Spirulina: towards technology of mineral feed supplements.

As one of the most widely used pesticides in agriculture, chlorothalonil can pose threat to soil ecosystems. Therefore, the impact of this substance on the development of microbiological and biochemical properties of the soil as well as on the growth of spring wheat was evaluated. The study was conducted with two soils (loamy sand with pHKCl 5.6 and sandy loam with pHKCl 7.00), to which fungicide was used in the following doses: 0.00, 0.166 (recommended dose), 1.660, and 16.60 mg kg−1 dry matter of soil (DM of soil). In addition, we determined the effectiveness of fertilizing substances (Lignohumat Super and Bioilsa N 12.5) in the restoration of soil homeostasis and chlorothalonil degradation in the soil. Chlorothalonil caused modifications in the count and biological diversity of soil microorganisms. It stimulated the growth of heterotrophic bacteria and actinobacteria, and inhibited the growth of fungi. This pesticide was a potent inhibitor of dehydrogenase, catalase and acid phosphatase activities. It showed variable effects on urease and alkaline phosphatase. The fungicide also a reduction the yield of dry matter of the aboveground parts of spring wheat. It should, however, be noted that these changes in the soil environment occurred after the introduction of higher doses of chlorothalonil. The fertilizing substances used contributed to enhanced microbial and biochemical activities of soils, while they did not significantly affect plant yields. The Bioilsa N 12.5 preparation was effective in chlorothalonil degradation, while Lignohumat Super reduced the degradation rate of the tested fungicide. Based on the conducted experiment, an ecological risk assessment of chlorothalonil was made by estimating the changes occurring in the soil environment evaluated through the microbiological and biochemical analyses of the soil.

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The influence of chlorothalonil on the activity of soil microorganisms and enzymes

Pesticides are a large and varied group of substances that are specifically designed to kill biological organisms including weeds, insects, and rodents. However, the extensive use of pesticides may result into their accumulation in the agricultural produce. Their low biodegradability has classified these chemicals as persistent toxic substances (Tayade et al., 2013). Fungicides, herbicides, insecticides, nematicides, rodenticides, fumigants, disinfectants, wood preservatives, and antifoliants are examples of pesticides (Puget Sound Water Quality Authority (PSWQA), 1991). About one third of the world s agricultural production is lost every year due to pests despite the pesticide consumption which is more than two million tons. In India pests cause crop loss of more than Rs 6000 crores annually, of which 33 per cent is due to weeds, 26 % by diseases, 20 % by insects, 10 % by birds and rodents and the remaining 11% is due to other factors (Rajendran, 2003). Pesticides are also used in industrial, domestic and marine environments. Pesticides are used globally and extensively for the control of pests (Bakiyaraj et al., 2014). The regular monitoring and control of pesticide usage in agriculture is very important because of the ISSN: 2319-7706 Volume 3 Number 10 (2014) pp. 23-33 http://www.ijcmas.com

https://www.ijcmas.com/vol-3-10/Kavita%20Rani%20and%20Geeta%20Dhania.pdf

Bioremediation and Biodegradation of Pesticide from Contaminated Soil and Water - A Noval Approach

Current perspective of innovative strategies for bioremediation of organic pollutants from wastewater.

Environmental pollution is a result of Industrial revolution. Environmental pollution effects quality of life and environmental ecosystem. Since decades, many attempts are being done to reduce environmental pollution. Among these attempts Bioremediation is one of the good remedial techniques. In the Bioremediation technique microorganisms are used to reduce the toxicity of harmful wastes and heavy metals from contaminated wastes water. Bioremediation has provided problem solving opportunities in the field of solid waste by detoxifying wastes. Due to its cost effectiveness and environmental impact offers attractive and more conventional clean-up technologies. In this regard researchers are carried out to study the effect of bioremediation by using various cyanobacteria species in reducing the toxicity. At this juncture this review glimpses the studies done in relation to removal of heavy metals in waste water by using Bioremediation techniques.

Bioremediation of heavy metals using spirulina

Plants never encounter stress factors, whether biotic or abiotic in sequence. Mostly they have to face multiple environmental factors in suboptimal level (stressful) at the same time. As a result, the strategy of the plant to survive in such situations demands handling of multiple stresses at the same time by efficient management of the genetic repertoire that the plant has. The plant achieves this by altering expression of transcription factors that regulate the activity of different genes, whose products themselves play the structural and functional roles. In the present study, differentially regulated genes under heat and drought stress from different microarray studies were analyzed to assess the kind of metabolic pathways that are specifically altered (promoted or sacrificed) under heat and drought stress and the transcription factor families which have the governing role in such regulatory processes. It was observed that expression of genes related to metabolism, specifically in the cell organelles like plastids and mitochondria is differentially regulated. Some transcription factor families like AP2-EREBP, NAC, C2H2 and MYB play more important role in the two kinds of stress conditions.

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O Murali

Papers

Bioremediation of heavy metals using spirulina

Effect of heat and drought stress on the expression of regulatory transcription factors and the genes involved in different metabolic pathways