Isolation, Identification And Characterization Of A DDTs-degrading Bacterium

1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane(DDT) is one of the persistent organic pollutants(POP) which were decided to control globally first by the UNEP due to its physical and chemical stability and recalcitrant degradation under natural conditions.DDTs,including 6 congeners and isomers,tends to accumulate in organisms.It had been proved that DDTs may cause cancer,malformation and mutation.Research of elimination of DDTs in the environments is of great significance to the health and sustainable development of mankind.In this paper,a new strain is isolated from the sludge using DDT analogue as substrate. Molecular,physiological and biochemical assays identify it as a member of Alcaligenes sp., named DG-5.Further research has been done systematically on degradation of DDTs by DG-5 and other DDTs-degrading bacteriums(DG-6,DG-M).The results as follows:(1) The degradation rate of DDTs achieved 94%,77%and 51%by Alcaligenes sp.DG-5 at the concentration for 0.5mg/L,5mg/L,15mg/L respectively.The co-metabolic substrate can promote the degradation in liquid effectively,and the effection from high to low is yeast extract,peptone andβ-cyclodextrin by turns.Inoculum size can influence the degradation rate. The greater concentration of bateria suspention,the higher degradation rate of inoculum size. The addition of formate can eliminate the inhibition phenomenon caused by the deficiency of NADPH in the course of degradation.Add the low concentrated formate can enhance effectively the degradation rate of DDTs,otherwise will cause inhibite.Moreover,for DDT and its analogues,the reactivity preference of DG-5 was not found.(2) DG-5,DG-6,DG-M could universally degrade HCB and other OCPs mentioned under aerobic conditions,which might be for reference to solve the complex pollution in the environments.JH-M,one of a PAH-degrading bacterium,could degrade chlorobenzoates in aerobic conditions.(3) For the soil system at the water ratio for 20%,50%,200%,it shows unsatisfied degradated effection.It was difficult to desorb DDTs from soil using activated carbon felt.This paper presented that Alcaligenes sp.DG-5 could effectively degrade DDTs under aerobic conditions,which might be holds the potential for use in bioremediation of DDT contaminated soils,waste deposits and water bodies.