Study On The Efficiency Of Dimethyl Phthalate (DMP) Degrading Functional Bacteria Group Screened From River Sediment

In some areas of China,there are refractory organic compounds such as dimethyl phthalate(DMP)in river sediments,which pose a serious threat to sediment ecosystem and human health.Indigenous microbial augmentation method has been widely used in the degradation of DMP in soil and other environments,and mainly a single strain.Sediment is a complex polluted environment,and it is more advantageous to degrade DMP in sediment by bacteria group.This paper aims to screen a DMP degrading bacteria group from river sediment,explore its optimal expansion culture conditions,and analyze its degradation characteristics in culture medium,and study its degradation perfomance in simulated sediment,so as to obtain a mixed bacteria that can efficiently degrade DMP in river sediment,and provide more technical and theoretical support for the removal of refractory organic matter such as DMP in river sediment.A functional bacteria group which can degrade DMP effectively was screened from the river sediment polluted by DMP.Novosphingobium(47.4%)was the most dominant species of the functional bacteria group,and its relative abundance was increased by about47%compared with the actual sediment.The growth kinetics equation of this functional bacteria group was in accordance with Andrews equation,and its degradation of DMP was in accordance with the first-order reaction kinetics equation.The results of single factor experiment showed that the optimal conditions of this functional bacteria group were as follows:p H of culture medium was 6,culture temperature was 35?,initial concentration of DMP was 500 mg/L,bacteria dosage was 3%,shaking speed was 140r/min,nitrogen source was peptone(nitrogen content was 450 mg/L).Under the optimal conditions,this bacteria group with OD₆₀₀ of 1.938 could be cultured within 22 h.The degradation characteristics of this functional bacteria group in culture medium were studied by single factor experiment.It has good tolerance to salinity and heavy metals,and can still degrade DMP in the environment containing 3%salinity,60 mg/L copper,150 mg/L zinc,30 mg/L lead,35 mg/L nickel or 5 mg/L chromium.The degradation pathways of this functional bacteria group to DMP are as follows:DMP is hydrolyzed to monomethyl phthalate,and then monomethyl phthalate is hydrolyzed to phthalic acid and corresponding alcohol;Phthalic acid is converted into protocatechuic acid by enzymatic reaction,and further decomposed into carbon dioxide and water.The experimental results showed that sodium acetate,glucose,methanol and starch could enhance the DMP degradation characteristics and growth ability of this functional bacteria group,and the enhanced stimulation effect of these four kinds of organic compounds was almost the same.The degradation efficiency of this functional bacteria group in simulated sediment environment was further studied.The results showed that this functional bacteria group could degrade DMP in simulated sediment efficiently.When the amount of bacteria was3%,this group could degrade 93.7%DMP(15 mg/kg)in the sediment environment with p H=6 and environment temperature of 35?.The addition of salinity and heavy metals in a certain range can effectively promote DMP degradation of DMP in sediment;When the degradation of DMP is beyond a certain range,the degradation ability of this functional bacteria group will be inhibited.This paper provides a kind of indigenous microorganism strengthening technology support for the degradation of DMP in river sediment.