Characteristics And Function Of S1in Degrading3,4-dichloroaniline

The3,4-dichloroaniline (DCA) is a type of chlorinated aniline compound, which is slightly soluble in water but soluble in most organic solven. DCA is widely used in the synthesis of organic products, such as dyes, drugs, and pesticides. It is also metabolites of several herbicides (e.g., diuron, linuron, and propanil) and has a higher toxicity than its parent compounds. Due to the fact that DCA is hard to be degradated, it accumulates in the environment. Therefore, eliminating the environment DCA residues becomes an urgent problem to be solved.A strain S1was isolated in this study and able to utilize DCA as a sole source of carbon and nitrogen for growth. By identifying the strain, analysing it’s degradation characteristics and preliminarily positioning the degradation function, I draw the following conclusions:1.30stains which can utilize DCA as a sole source of carbon and nitrogen for growth was isolated from11kinds of soil and water samples collected. The strain S1had the highest degradation rate of DCA, it was up to63.82%. Based on the morphology, physiological biochemical characteristics, and16S rDNA sequence analysis, the strain was identified as Pseudomonas putida.2.The degradation characteristics of S1was analyzed via single factor test and orthogonal test. The single factors test mainly studied the influence of factors(including tempreture, pH value, initial concentration of DCA and the inoculation amount) on degradation rate. The results showed that:The best degradation tempreture was31℃, pH value was7.0and DCA initial concentration was30mg/L; When the inoculation amount was equal or greater than3mL, the growth of degradation rate was not obvious, the rising trend tended to be stable; These four factors had larger influence on the degration rate of DCA.3.This study selected30mg/L as DCA test concentration. Through the orthogonal test of three factors (tempreture, pH value and the inoculation amount) and three levels, the following results were founded:The pH value had the biggest influence on DCA degration rate; The optimal combination of degradation conditions was31℃(temperature),7.0(pH value) and4mL (inoculum amount). In this condition, DCA degradation rate reached67.45%.4.The plasmid elimination and transformation experiments proved that:S1contains a plasmid with a size of greater than10kb. As the plasmid was lost, the loss of the degradation ability of strain S1. When the plasmid was transferred into Escherichia coli BL21and back into plasmid-removed S1, the transformants obtained the ability to degrade DCA. These observations indicated that the plasmid of strain S1is responsible for the degradation of DCA.