Degradation of fipronil by Stenotrophomonas acidaminiphila isolated from rhizospheric soil of Zea mays.
Fipronil is a widely used insecticide in agriculture and can cause potential health hazards to non-target soil invertebrates and nearby aquatic systems. In the present study, a fipronil degrading bacterium was isolated from fipronil contaminated soil, i.e. rhizospheric zone of Zea mays. Morphological, biochemical and molecular characterization of strain indicated that it clearly belongs to Stenotrophomonas acidaminiphila (accession no. KJ396942). A three-factor Box-Behnken experimental design combined with response surface modeling was employed to predict the optimum conditions for fipronil degradation. The optimum pH, temperature and total inocula biomass for the degradation of fipronil were 7.5, 35 °C and 0.175 g L-1, respectively. The bacterial strain was able to metabolize 25 mg L-1fipronil with 86.14 % degradation in Dorn's broth medium under optimum conditions. Metabolites formed as a result of fipronil degradation were characterized with gas liquid chromatograph. A novel fipronil degradation pathway was proposed for S. acidaminiphila on the basis of metabolites formed. Non-sterilized soil inoculated with S. acidaminiphila was found to follow first order kinetics with a rate constant of 0.046 d-1. Fipronil sulfone, sulfide and amide were formed as the metabolites and were degraded below the quantifiable limit after 90 days of time period. Given the high fipronil degradation observed in the present study, S. acidaminiphila may have potential for use in bioremediation of fipronil contaminated soils.
Department of Environmental science, Swami Ramtirth campus Badshahithaul, Hemwati Nandan Bahuguna Garhwal University, Srinagar Garhwal, Uttarakhand, India. shivi273@gmail.com.
Shivani
S
Uniyal
Ecotechnology laboratory, Department of Environmental Science, G. B. Pant University of Agriculture and Technology, Pantnagar, India.
Rashmi
R
Paliwal
G. B. Pant Institute of Himalayan Environment and Development, Himachal Unit, Mohal-Kullu, Himachal Pradesh, India.
R K
RK
Sharma
Ecotechnology laboratory, Department of Environmental Science, G. B. Pant University of Agriculture and Technology, Pantnagar, India.
J P N
JPN
Rai
Bioremediation; Box–Behnken design; Fipronil; Soil; Stenotrophomonas acidaminiphila