Screening And Degradation Characteristics Of Dibutyl Phthalate Degrading Bacteria

Dibutyl phthalate(DBP),as a common organic compound,is widely used as plasticizer added to various industrial products.It pollutes water,soil and atmosphere to varying degrees.EPA,EU and China Environmental Monitoring Station rank DBP as a priority pollutant.Therefore,to solve the problem of DBP pollution in the environment is of great scientific significance for the protection of the ecological environment.At present,biodegradation is considered to be the most effective way to degrade DBP.In this paper,Dibutyl phthalate(DBP)was taken as the research object.The conditions of ultrasonic extraction and GC-MS detection of DBP were optimized.A strain with high DBP degradation effect,named as DP-2,was screened from the activated sludge of a sewage treatment plant.On this basis,the growth and degradation conditions of the strain were optimized.Finally,pot experiments were carried out to study the effect of strain DP-2 on the restoration of DBP-contaminated soil and the effect of degradation bacteria on the growth of Chinese cabbage under DBP stress.This rsearch can provide a scientific basis for the remediation of DBP contaminated soil.The main results are as follows:?(1)The extraction conditions were optimized from three aspects: selection of extractant,extraction time and extraction temperature.Finally,n-hexane: ethyl acetate(V: V,1:1)was selected as extractant,the extraction time was 30 minutes,and the extraction temperature was set to 40?.The collision energy was optimized to obtain the highest response in the quantitative detection of GC-MS,and the optimal collision energy was 25 eV.(2)A strain named DP-2 with high DBP degradation effect was screened from the activated sludge of a sewage treatment plant.It was identified as Acinetobacter sp.(3)Experiments on optimizing the growth conditions of strains were carried out.It was showed that the strains grew best when the pH was 8,the temperature was 30 C,and the shaking speed was 150 rpm,respectively.The optimization test of the degradation conditions of the strain was carried out.It showed that the initial degradation rate of DBP was the highest when inoculation amount was 20%.The degradation rate decreased gradually with the increase of initial DBP concentration.The highest degradation rate was 97.83% at NaCl concentration of 5 g/L.Glucose promoted degradation most obviously.The optimal degradation conditions of strain DP-2 were studied by response surface methodology.It showed that the optimum degradation conditions of DP-2 were salinity 5 g/L,inoculation amount 17.14%,substrate concentration 9.81 mg/L.The theoretical value of degradation rate predicted by the model was 86.81%.And the verification experimental result was 85.86%,which was close to the predicted value.(4)Pot experiments on DBP degradation in soil by strains showed that DBP-contaminated soil had a certain stress effect on the growth of Chinese cabbage.At,the biomass of cabbage decreased by 58.77% compared with the blank control after 30 days cultivation.The inoculation of DP-2(DBJ,GBJ)could alleviate DBP stress effect,and the biomass of Chinese cabbage was 20.34%-23.83% higher than that of non-inoculated treatment.Compared with non-inoculated treatment,the DBP concentration in roots,stems and leaves of Chinese cabbage treated by inoculation decreased to a maximum of 23.86%.The treatment of planting Chinese cabbage and DP-2 inoculation could reduce DBP concentration in soil.For the low and high concentration treatments,the removal efficiency of DBP in soil by planting Chinese cabbage and inoculating bacteria reached 46.63% and 30.77%,respectively.Through the above research,a strain with high degradation effect on DBP was screened,and the growth conditions(temperature,pH,shaking speed)and degradation conditions(inoculation amount,substrate concentration,salinity,carbon source)were optimized.The effect of strain on the repair of DBP contaminated soil was clarified.The results provide theoretical basis and technical support for the restoration of DBP contamination by functional microorganisms.