Abstract
Bacterial isolates RP-1, RP-3 and RP-9 were isolated from agricultural soil using enrichment culture technique and screened positive for lindane degradation. RP-1, RP-3 and RP-9 were found to utilize and degrade higher concentrations (100 ppm) of lindane. RP-1 and RP-3 showed 69.5 and 65% lindane degradation after 10 days of inoculation where as RP-9 degraded 62% of lindane after 15 days. The estimated Cl- ion release was 49, 42 and 39 mg/mL, respectively for the three bacterial isolates. Gas chromatography was used for analysis of metabolite formed during lindane degradation and different parameters of degradation kinetics were calculated using first order kinetic equation. A drastic decrease in degradation rate was observed at initial lindane concentrations higher than 200 mg/l in the mineral media. The calculated half-life periods for RP-1, RP-3 and RP-9 were found to be 3.85, 2.77 and 4.00 days, respectively. All three isolates showed maximum degradation activity at: incubation period; 10-15 days, incubation temperatures; 30°C, pH; 7.0, shaking speed 120 rpm, initial substrate concentration; 100 mg/l. Galactose and succinate enhanced the degradation rate up to 10% whereas maltose, lactose and xylose decreased the degradation level up to 40%. Addition of glucose as a co-substrate was found highly favorable for enhancement of lindane degradation. Key words: Enrichment culture, colorimetric assay, lindane, degradation, gas chromatography.
Highlights
The use of pesticides has increased dramatically during the last two decades at global level, due to their promising effects in agricultural and other related areas.Some of these are extremely resistant to biodegradation by native flora when compared with the naturally occurring compounds that are readily degraded upon introduction into the environment
First order kinetic equation was used for calculating different parameters of lindane degradation by fitting experimental data: Ct = C0e
Bacterial isolates RP-1, RP-3 and RP-9 isolated from agricultural soil have been found to possess the ability to utilize and degrade higher concentrations of lindane
Summary
The use of pesticides has increased dramatically during the last two decades at global level, due to their promising effects in agricultural and other related areas. Some of these are extremely resistant to biodegradation by native flora when compared with the naturally occurring compounds that are readily degraded upon introduction into the environment. Pesticides residues and their transformation products are frequently found in the environmental matrices. Despite concerns regarding their toxicity to humans and wildlife along with their relative stability to sediments and soil, they are still widely used (Diez, 2010). The HCH formulation consists of γ-(10–12%), α- (60–70%), β- (5–12%) and δ- (6–10%) isomers
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