CYPERMETHRIN DEGRADATION USING KLEBSIELLA PNEUMONIAE AND CHECKING TOXICITY OF DEGRADATION PRODUCTS ON AQUATIC LIFE

Agricultural loss due to different pests is increasing extensively. Various chemical pesticides like organophosphorus pesticides, organochlorines, carbamates are being used for control of the various pests. But these pesticides are found to be associated with different side effects and toxicity to human beings and to aquatic life. So, these pesticides have been banned for use by many countries. Therefore, synthetic pyrethroids are being used extensively in the agriculture after the ban over organochlorine and organophosphorous pesticides. Cypermethrin is the fourth generation pyrethroid useful against pests of fruits, vegetables and household insects. Cypermethrin shows affectivity against different pests at low concentration but at the same time shows toxicity to human beings and to aquatic life. So, removal of these pesticides from soil is very important for crop protection. Focus of this paper is degradation of cypermethrin by using rhizospheric isolates. For this, different isolates were obtained from soil samples and checked for their capacity of cypermethrin degradation. Two isolates showing capacity of cypermethrin degradation were identified by 16S rRNA. One of the isolate K. pneumoniae was used for cypermethrin degradation. Cypermethrin degradation was confirmed by detecting reduction in the COD values. COD value was found to reduced more than 50%. Cypermethrin degradation metabolites were detected by GC-MS analysis and different degradation metabolites were identified by comparing with standard database. Toxicity of the cypermethrin degradation product was tested by fish bioassy. It was found that guppy fishes could survive up to 48 hrs in presence of cypermethrin degradation product whereas in control fishes were died within half hour.

不同虫害引发的农业损失正持续大幅攀升。当前各类化学农药，如有机磷农药（organophosphorus pesticides）、有机氯农药（organochlorines）、氨基甲酸酯类农药（carbamates）等，被广泛应用于虫害防治。但研究证实，此类农药会引发多种副作用，且对人类及水生生物具有毒性，因此多国已明令禁止其使用。在有机氯与有机磷农药被禁用后，合成拟除虫菊酯类农药（synthetic pyrethroids）在农业生产中得到广泛应用。氯氰菊酯（cypermethrin）作为第四代拟除虫菊酯类农药，可有效防治果蔬害虫与居家虫害。尽管氯氰菊酯在低浓度下即可对多种害虫展现出灭杀活性，但同时也会对人类及水生生物产生毒性，因此从土壤中去除此类农药对作物保护而言至关重要。本研究聚焦于利用根际分离菌株（rhizospheric isolates）降解氯氰菊酯。为此，研究人员从土壤样本中分离得到多株菌株，并对其降解氯氰菊酯的能力进行了筛选。通过16S核糖体RNA（16S rRNA）测序，鉴定出两株具备氯氰菊酯降解能力的菌株，其中一株为肺炎克雷伯菌（K. pneumoniae），并将其用于氯氰菊酯降解实验。通过检测化学需氧量（COD）值的降幅，验证了氯氰菊酯的降解效果，结果显示COD值降幅超过50%。研究采用气相色谱-质谱联用仪（GC-MS）分析检测到氯氰菊酯的降解代谢产物，并通过比对标准数据库鉴定出多种降解产物。通过鱼类生物毒性实验检测氯氰菊酯降解产物的毒性：结果表明，孔雀鱼在含有该降解产物的水体中可存活长达48小时，而对照组孔雀鱼仅在半小时内便全部死亡。