“Studies on Bioremediation of Isoprothiolane, fungicide/insecticide and Glyphosate, a herbicide and Monitoring of Biodegradation using Biosensors

Arul Selvi, A. (2011) “Studies on Bioremediation of Isoprothiolane, fungicide/insecticide and Glyphosate, a herbicide and Monitoring of Biodegradation using Biosensors. Doctoral thesis, University of Mysore.

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Abstract

Glyphosate [N-(phosphonomethyl) glycine] is a broad-spectrum, non selective, systemic, post-emergence herbicide used both agriculturally and domestically. It is the active ingredient in a number of commercial herbicides produced by Monsanto, Cheminova, and Zeneca Corp. Glyphosate is a member of the amino acid herbicide family, and its mode of action is through inhibition of 5-enolpyruvylshikimate- 3-phosphate synthase (EPSP), an enzyme of the shikimic acid pathway. This enzyme is important in the biosynthesis of the aromatic amino acids phenylalanine, tyrosine, and tryptophan. A blockage of the shikimic acid pathway leads to a depletion of the free pool of aromatic amino acids in higher plants consumption of it results in symptoms such as intestinal pain, vomiting, excess fluid in the lungs, pneumonia, clouding of consciousness, and destruction of red blood cells. Short term exposure to glyphosate can cause breathing difficulties, loss of muscle control and convulsions. Isoprothiolane (di-isopropyl 1, 3-dithiolan-2-ylidenemalonate), a systemic fungicide, is effective against Pyricularia oryzae, which causes blast disease in rice. It is applied at 3.2–4.8 kg/ ha. Because of a high rate of application, there is an appreciable risk of ground water and surface water contamination by isoprothiolane, particularly in the agro-climatic zone having light soil and high rainfall. With continuous usage, these pesticides enter the human body via food chain. Residues of these pesticides have been detected in soil, water and air. A microbial consortium capable of degrading glyphosate and isoprothiolane was isolated in the laboratory by long term enrichment. The consortium was made of 10 bacterial isolates of which 7 belonged to Pseudomonas sp. and one each of Flavobacterium , Vibrio and Burkholderia sp. Conditions were optimized by response surface methodology. The maximum predicted percentage degradation of 100, 100, 100, 82 and 73 was obtained respectively for, 20, 40, 50, 75 and 100 ppm initial glyphosate concentrations at pH 6.60 with an incubation temperature of 30 0C and inoculum concentration of 1146 g protein/ml. Similarly the maximum predicted percentage degradation of 100, 100, 100, 100 and 95.5 was obtained respectively for 5, 10, 20, 30 and 50 ppm initial isoprothiolane concentrations at pH levels 7.7, 6.8, 6.2, 4.7 and 4.6 with an incubation temperature of 30 0C and inoculum concentration of 50 g protein/ml. The degradation of these pesticides by the microbial consortium increased with time. The degradation reached 100% by 120 h of incubation for these pesticides. Residues of glyphosate and isoprothiolane are generally analyzed by thin layer chromatography, gas chromatography and High performance liquid chromatography which are expensive, labour intensive, require extensive clean up and are not suited for on field assay. Immunoassay is highly sensitive, specific, on- field method, does not need sample clean up and has high throughput of samples. In our lab we attempted to develop an immunoassay for the detection of glyphosate and isoprothiolane by using avian antibodies. Glyphosate and isoprothiolane levels up to 2 ng could be detected by Well- Dot. Signal amplification improved the detection signal with the same sensitivity. Immunosensor based on DNA coated CdS nanoparticles and antibody coated CdS nanoparticles were developed for the detection of glyphosate and isoprothiolane. The detection limit by these nanoparticles based methods was 0.2 ng /ml.

Item Type:	Thesis (Doctoral)
Uncontrolled Keywords:	Glyphosate, herbicide, degradation, microbial consortium
Subjects:	500 Natural Sciences and Mathematics > 04 Chemistry and Allied Sciences > 26 Pesticide Chemistry 600 Technology > 05 Chemical engineering > 01 Biotechnology and Bioengineering
Divisions:	Fermentation Technology and Bioengineering
Depositing User:	Food Sci. & Technol. Information Services
Date Deposited:	14 May 2012 09:42
Last Modified:	19 Jan 2021 07:01
URI:	http://ir.cftri.res.in/id/eprint/10738

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