Effect of In Situ Bioremediation of Soil Contaminated with DDT and DDE by Stenotrophomonas sp. Strain DXZ9 and Ryegrass on Soil Microorganism

In the present study, the changes in the microbial populations, enzyme activity and bacterial community structure in contaminated soils were investigated during the bioremediation of using Stenotrophomonas sp. strain DXZ9 and ryegrass. The results showed that the removal rates were 81% for DDT and 55% for DDE (69% for DDTs) with ryegrass-microbe. Microbial activity was remarkably improved, and the number of bacteria increased sharply from 7.32 × 106 to 2.56 × 108 cells/g in the 10 days due to successful colonization of the strains and effects of the ryegrass rhizosphere. There was significant difference in fungi number with ryegrass when comparing the 30th and 90th days with the 210th day: The actinomycete number in the soil with ryegrass was higher than without ryegrass, and it indicated that the number of microorganisms significantly increased under the action of ryegrass. The activities of polyphenol oxidase, dehydrogenase and catalase were significantly activated by the combination of ryegrass and microbe, and urease activity was less affected: It has influence on the diversity of bacterial community structure in the soil, but its influence gradually decreased by denaturing gradient gel electrophoresis with an extension in time. The activities represented promising tools for decontaminating and restoring the ecosystem in sustainable ways, and proposing new approaches and technological bottlenecks to promote DDT biodegradation is very significant.