Abstract
Intensive use of chlorpyrifos has resulted in its ubiquitous presence as a contaminant in surface streams and soils. It is thus critically essential to develop bioremediation methods to degrade and eliminate this pollutant from environments. We present here that a new fungal strain Hu-01 with high chlorpyrifos-degradation activity was isolated and identified as Cladosporium cladosporioides based on the morphology and 5.8S rDNA gene analysis. Strain Hu-01 utilized 50 mg·L−1 of chlorpyrifos as the sole carbon of source, and tolerated high concentration of chlorpyrifos up to 500 mg·L−1. The optimum degradation conditions were determined to be 26.8°C and pH 6.5 based on the response surface methodology (RSM). Under these conditions, strain Hu-01 completely metabolized the supplemented chlorpyrifos (50 mg·L−1) within 5 d. During the biodegradation process, transient accumulation of 3,5,6-trichloro-2-pyridinol (TCP) was observed. However, this intermediate product did not accumulate in the medium and disappeared quickly. No persistent accumulative metabolite was detected by gas chromatopraphy-mass spectrometry (GC-MS) analysis at the end of experiment. Furthermore, degradation kinetics of chlorpyrifos and TCP followed the first-order model. Compared to the non-inoculated controls, the half-lives (t 1/2) of chlorpyrifos and TCP significantly reduced by 688.0 and 986.9 h with the inoculum, respectively. The isolate harbors the metabolic pathway for the complete detoxification of chlorpyrifos and its hydrolysis product TCP, thus suggesting the fungus may be a promising candidate for bioremediation of chlorpyrifos-contaminated water, soil or crop.
Highlights
Synthetic organophosphates (OPs) are the most frequently and widely used insecticides, accounting for an estimated 34% of world-wide insecticide sales [1,2]
Phylogenetic analysis of the 5.8S rDNA gene sequences revealed that strain Hu-01 grouped among Cladosporium species and was closely related to C. cladosporioides strain ATT097 (GenBank accession No H607834) and C. cladosporioides strain CY141 (GenBank accession No HQ607983) with high identities (.99%) (Fig. 2)
A novel fungal strain C. cladosporioides strain Hu-01 responsible for chlorpyrifos degradation was isolated from organophosphatecontaminated soils using an enrichment procedure
Summary
Synthetic organophosphates (OPs) are the most frequently and widely used insecticides, accounting for an estimated 34% of world-wide insecticide sales [1,2]. Most organophosphorus insecticides share a similar structure, containing three phosphoester linkages and are often termed phosphotriesters [3] This class of pesticides have acute neurotoxicity attributing to their ability to suppress acetylcholinesterase (AchE) [4], and various clinical effects can occur due to their poisoning in human beings [5,6,7,8,9]. Chlorpyrifos, [O,O-diethyl O-(3,5,6-trichloro-2-pyridyl) phosphorothioate] is one of the most extensively used broad-spectrum OPs, and its phosphorus is linked to a sulfur with a double bond (P = S) (Fig. 1). It is registered for use on lawns, ornamental plants, animals, domestic dwellings as well as commercial establishments [11]
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