title: Microbial detoxification of bifenthrin by a novel yeast and its potential for contaminated soils treatment.
abstract: Bifenthrin is one the most widespread pollutants and has caused potential effect on aquatic life and human health, yet little is known about microbial degradation in contaminated regions. A novel yeast strain ZS-02, isolated from activated sludge and identified as Candida pelliculosa based on morphology, API test and 18S rDNA gene analysis, was found highly effective in degrading bifenthrin over a wide range of temperatures (20-40 °C) and pH (5-9). On the basis of response surface methodology (RSM), the optimal degradation conditions were determined to be 32.3 °C and pH 7.2. Under these conditions, the yeast completely metabolized bifenthrin (50 mg · L(-1)) within 8 days. This strain utilized bifenthrin as the sole carbon source for growth as well as co-metabolized it in the presence of glucose, and tolerated concentrations as high as 600 mg · L(-1) with a q(max), K(s) and K(i) of 1.7015 day(-1), 86.2259 mg · L(-1) and 187.2340 mg · L(-1), respectively. The yeast first degraded bifenthrin by hydrolysis of the carboxylester linkage to produce cyclopropanecarboxylic acid and 2-methyl-3-biphenylyl methanol. Subsequently, 2-methyl-3-biphenylyl methanol was further transformed by biphenyl cleavage to form 4-trifluoromethoxy phenol, 2-chloro-6-fluoro benzylalcohol, and 3,5-dimethoxy phenol, resulting in its detoxification. Eventually, no persistent accumulative product was detected by gas chromatopraphy-mass spectrometry (GC-MS) analysis. This is the first report of a novel pathway of degradation of bifenthrin by hydrolysis of ester linkage and cleavage of biphenyl in a microorganism. Furthermore, strain ZS-02 degraded a variety of pyrethroids including bifenthrin, cyfluthrin, deltamethrin, fenvalerate, cypermethrin, and fenpropathrin. In different contaminated soils introduced with strain ZS-02, 65-75% of the 50 mg · kg(-1) bifenthrin was eliminated within 10 days, suggesting the yeast could be a promising candidate for remediation of environments affected by bifenthrin. Finally, this is the first described yeast capable of degrading bifenthrin.
authors.affiliation: Laboratory of Insect Toxicology, Key Laboratory of Pesticide and Chemical Biology, Ministry of Education, South China Agricultural University, Guangzhou, People's Republic of China.
authors.forename: Shaohua
authors.initials: S
authors.lastname: Chen
authors.forename: Jianjun
authors.initials: J
authors.lastname: Luo
authors.forename: Meiying
authors.initials: M
authors.lastname: Hu
authors.forename: Peng
authors.initials: P
authors.lastname: Geng
authors.forename: Yanbo
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D001673:Biodegradation, Environmental; D011722:Pyrethrins / Q000378:metabolism* / Q000633:toxicity; D012722:Sewage / Q000382:microbiology; D012989:Soil Pollutants / Q000378:metabolism*; D015003:Yeasts / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D011722:Pyrethrins; D012722:Sewage; D012989:Soil Pollutants; C099952:bifenthrin