Isolation, Identification And Degrading Characterization Of DDT Degrading Bacterium

Concentrating on the organochlorine pesticide DDT, the research takes samplesfrom DDT polluted soil of a shipyard in Guanzhou. Eight strains that can degrade DDTare isolated after enrichment cultured and filtered. With initial study on morphology,physiological and biochemical characteristics, fatty acid identification and16S rDNAmolecular biology identification, the content of the research is as follow:Eight strains of DDT degrading bacteria that use DDT as the sole carbon source areisolated from DDT polluted soil through enrichment culture and streak plate method. Bystudy on morphology, physiological and biochemical characteristics, fatty acididentification and16S rDNA molecular biology identification, the strains are identified.Strains numbered5~#and6~#belong to Delftia sp.,20#belongs to Thauera sp.,12-1~#belongs to Alcaligenes sp., and23~#,24~#,12-2~#,12-3~#belong to Pseudomonas sp..Analysing condition of DDT is set up using high performance liquidchromatograph at the analysing temperature of25℃, with99.9%methanol as themobile phase, and a floe rate at1ml/min, so that the peak at254nm is explored. Thefinal DDT degration rate of the eight strains are measured through external standardmethod. At30℃,pH7.0, and a culture condition with a DDT concentration of20mg/L,all of the strains have a certain effeciency of DDT degrading, the rates of which reachhigher than10%. The strain12-3~#has the highest rate, which can reach51.6%in8hours.Using turbidimetry to study the growth status of the eight strains and the degradingcurves show that all the eight strains can degrade DDT at different degrees, strains of5~#,6~#,23~#and12-1~#have faster rate of growth, and can reach the maximum absorbance in12h, which means the concentration of bacteria reaches the maximum, followed by thestationary phase; strains of20#and24#have slower rate of growth, and reach themaximum absorbance in22h and28h respectively. Strains of12-2~#and12-3~#have theslowest rate of growth, and reach the maximum absorbance in30h. At the culturecondition of30℃, DDT concentration of20mg/L, using shake cultivation at150r/minfor8days. The strain of12-3~#has the best degration rate. Protein content of the eight strains are measured through coomassie brilliant blueG-250method. The strain of5~#has the highest content, which is73.118μg per ml ofbacteria solution. On the contrary,20~#has the lowest content of64.345μg per ml.