International Research Journal of Engineering and Technology (IRJET) Volume: 04 Issue: 02 | Feb -2017
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e-ISSN: 2395 -0056 p-ISSN: 2395-0072
Characterization of chromium bioremediation by Stenotrophomonas maltophilia SRS 05 isolated from tannery effluent. N. Shobana Sundari1 1 Assistant
Professor, Department Of Biotechnology, RVS College Of Arts & Science, Sulur, Coimbatore, Tamil Nadu, India.
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Abstract - Chromium is an essential micronutrient that is
Chromium is an essential mineral directly involved in carbohydrate, fat, and protein metabolism, However, at high concentration it is toxic, carcinogenic and tetratogenic. It is the major pollutants being discharged from various industries (electroplating, chromate manufacturing, dyes and pigment manufacturing, wood preservation, stainlesssteel production, leather tanning industry, manufacture of alloys and as corrosion inhibitor in conventional and nuclear power plants.) during mechanical operations. They mix in the water bodies and make them unusable.
toxic when present in high levels. Toxicity of chromium has been also associated with cancer and as a disruption to cellular functions. The present study dealing with an approach to remediate chromium from the environment is carried out using tannery effluent. Yellow bacterial colonies were selected from the mass of colonies obtained on serial dilution of tannery effluent samples. The bacteria was identical as Stenotrophomonas maltophilia SRS05 by 16SrRNA sequencing. The sequence of Stenotrophomonas maltophilia SRS05 was submitted to the NCBI and obtained the Accession number KF558319. The hexavalent chromium remediation ability of Stenotrophomonas maltophilia SRS05 was studied and quantify the chromium (VI) in the tannery effluent using Atomic absorption spectroscopy method and was observed at the 15th day of incubation. FTIR and SEM analysis revealed some irregular fragments on the adjoining cell surfaces indicating slight morphological changes on cellular surface of the identified bacterium. The bioremediation process of the above study concluded that the Stenotrophomonas maltophilia SRS05 could be used as a promising agent for the removal of Cr(VI) in effluents.
Among all industrial wastes, tannery effluent are ranked as the highest pollutants and large contributors of chromium pollution. In India alone about 2000–3000 tones of chromium escapes into the environment annually from tannery industries, with chromium concentrations ranging between 2000 and 5000 mg/l in the aqueous effluent compared to the recommended permissible discharge limits of 2 mg/l (Altaf et al., 2008). If it exceeds the permissible discharge limit the hexavalent chromium compounds in the effluent pose health risks to humans, plants, animals and fishes (Lee and Jones, 1998; Srinath et al., 2002). People are facing various health problems by being exposed to the polluted water. Due to its carcinogenicity and mutagenicity, the United States Environment Protection Agency (USEPA) has designated Cr as a “Priority pollutant” or Class A” pollutant (Srinath et al., 2002; Lee and Jones, 1998). At high levels, heavy metals like chromium damage cell membranes, alter enzyme specificity; disrupt cellular functions and damage structure of DNA (Bruins et al., 2000). Cr(VI) activates p53 by reactive oxygen species (ROS) mediated free radical reactions that occur during the oxidative reduction of hexavalent Cr within the cell. Oxidative damage is considered to be an important mechanism in the genotoxicity of Cr(VI). Hence, the need arises to remediate chromium before being discharged.
Key Words : 1. Hexavalent Chromium remediating microorganisms - Stenotrophomonas maltophilia, 2. potassium dichromate, 3. 1,5-diphenylcarbazide (DPC), 4. Spectrophotometer, 5. Bioadsorption studies, 6. Statistical tool - Plackett-Burman design and Box-Behnken factorial design, 7. Bioremediation, 8. Atomic absorption spectroscopy and SEM analysis.
1. INTRODUCTION Chromium is a refractory metal and is a first element in the Group 6 of the periodic table, It’s a hard and brittle metal with high melting point and many of it compounds are intensly coloured. Louis Nicolas Vauquelin first isolated chromium metal from this mineral in 1798 (Barceloux, 1999). Chromium exhibits a wide range of possible oxidation states, where the +3 state is most stable energetically; the +3 and +6 states are most commonly observed in chromium compounds. The Hexavalent chromium are more toxic than Trivalent chromium compounds in terms of its Solubility in water, Permeability through biological membrane and its interaction with cellular proteins and Nucleic acids (Sultan and Hasnain, 2005).
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Chromium remediation is an environmental challenge. Conventional methods used for the removal of hexavalent Cr are expensive and lack specificity (Katiyar and Katiyar, 1997). Recently, bioremediation is emerging as a safe and an alternative to the traditional physicochemical methods. Bioremediation is the microbial clean up approach to remove the inorganic pollutants from the contaminated site such as water, soils, sludges, and waste streams, in situ or ex situ. Hence the present investigation primarily involves the simultaneous removal of chromium in tannery effluent using
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