ABSTRACT
A novel yeast strain, Atz-EN-01 isolated from contaminated-agricultural soil was found to be highly effective in degrading atrazine in liquid culture and soil. The molecular characterization based upon partial 18S rDNA and ITS regions identified the strain Atz-EN-01 as Pichia kudriavzevii. The yeast could degrade atrazine completely within 7 days with a rate constant of 0.31 per day following the first order kinetic model. The time in which initial atrazine concentration (500 mg/L) was reduced by 50% (half-life) was 2.2 days under optimal conditions (pH 7.0, temperature 30˚ C, inoculum size 3% (v/v) and shaking speed 120 rpm). The analysis of the metabolites using GC-MS identified the formation of 3 intermediates viz. hydroxyatrazine, N-isopropylammelide and cyanuric acid. The enzyme atrazine chlorohydrolase exhibited maximum activity during degradation. Based upon the intermediates identified by GC-MS and FT-IR analysis, the sequential process of atrazine degradation was proposed. In soil bioremediation experiment, inoculation of soil with Atz-EN-01 promoted effective degradation than did the control. To the best of our knowledge, this is the first report on Pichia kudriavzevii strain Atz-EN-01 which can serve as a potential agent for in-situ bioremediation of atrazine contaminated environment.