The Characteristics Of DBP Degradation Strain DNB-S1 And Feeding Behavior Research

Di-n-butyl phthalate(DBP) is a kind of plasticizer in the plastic, belongs to Phthalate ester(PAEs),which is widely employed in industry, agriculture and daily life. DBP is easily released into the environment, and damage to the environment, threaten human life and health. In this research, I mainly focus on the DBP degrading bacteria of Novosphingobium aromaticivorans DNB-S1, and research the characteristics of strain DNB-S1 growing and degrading, and primarily explore its ingestive behavior. The main research results are as follows:(1) The growth rate of the strain DNB-S1 is different under different nutrient condition, the sequence of the growth rate from fast to slow: LB>MSM-Glu>MSM-DBP+Glu>MSM-DBP. The DBP degradating effect of strain DNB-S1 is affected by pH and temperature, the degradation rate is the highest under the pH of 7.0 or temperature of 35℃, in 48 h the strain DNB-S1 can degrade the 86.4 % DBP.(2) The strain DNB-S1 can degrade DBP, DMP, DEP and DEHP, it can degrade 500 mg/L DBP, DMP, DEP and DEHP respectively more than 95%, 95%, 84% and 60% within 72 h. The four kinds of mixed PAEs can cultivate strain DNB-S1, and the strain DNB-S1 can grow in good condition, and the PAEs of strain has no toxic effects on the strains. It can degrade 125 mg/L DBP, DMP, DEP and DEHP respectively more than 93%, 88%, 97% and 71% within 5 days. The four kinds of mixed PAEs in 500 mg/L can degrade degrade more than 88 % of the DBP.(3) The strain DNB-S1 can grow well in various condition, the wall of cell is smooth, the structure of cell’s outer and inner membranes is complete without soluble membranes; the cytoplasm is full, the ribosomes along cell inner membrane show quite uniformed distribution, the nucleus form is normal without variation. When the culture system is under the condition of DBP, the peptidogly layer outside of the strain DNB-S1 cell will disappear.(4) The strain DNB-S1 can adjust its CSH according to different environment and different DBP content, the strain CSH in the MSM culture medium or MSM-DBP+Glu culture medium is up to 79.8 % at the beginning of the cultivation, and it is stably at around 50% in 3 days; the strain CSH in the MSM-Glu culture medium is up to 26.9 % at the beginning of the cultivation, and it is stably at around 50% in 3 days; the strain CSH in the LB culture medium always keeps 9.3 %-13.4 % in 7 days, and the pH and temperature of culture medium has certain influence on the strain DNB-S1. The CSH is higher in the acid environment or the temperature of 30-35℃.(5) In the initial concentrations of DBP with 100 mg/L we culture the strain for 72 h, the DBP content of the whole degradation system and the extracellular fluid shows a trend of gradual decline with time. At the beginning of the culture stage, the surface of the strains rapidly accumulate DBP, when the accumulation reaches 1.2 mg/L, the accumulation DBP content of the cell surface will gradually decline with time, after 72 h it will drop to below 0.3 mg/L; Then the DBP content of bacteria cells will increase with cultivation time, and become basically stable within 48-72 h, which shows that DBP can smoothly enter the bacteria cells and is continuously used and degraded.(6) Whether or not the cultivation system has the DBP, the hydrophilic group kinds of strain DNB-S1 remains constant. When there is DBP in the cultivation system, the surface membrane of strain DNB-S1 will generate the hydrophobic groups of C-H and R-COOH. When there is no DBP in the cultivation system, the hydrophobic groups will disappear.