Study On Degradation Of Organic Compounds By Soil-Bacteria Providencia Sp.LLDRA6 And Biogenic Mn Oxides

As the strongest oxidant,only next to oxygen on the earth,Mn oxide minerals are widely distributed in terrestrial soils,marine sediments and aquatic environment.Naturally occurring Mn(?)oxidation,including biotic and abiotic pathways,constantly drives the formation of Mn oxides in the crustal layer.The biological oxidation pathway of Mn oxides in natural environment is generally considered to be closely related to the microbial activities.Up to now,the evidence of Mn oxide minerals formation by biogenic oxidation mainly comes from marine and lacustrine facies.The mechanism of microbe-mediated Mn(?)oxidation has been studied mainly around three type model strains.However,the primary products of Mn(?)oxidation are almost all hexagonal birnessite with the poorly crystalline and high valence.In this study,highly active Mn-oxidizing bacteria isolated on the basis of previous laboratory research were selected.An array of techniques,such as scanning electron microscope(SEM),powder X-ray diffraction(XRD),high resolution transmission electron microscope(HRTEM),specific surface area(SSA)and X-ray photoelectron spectroscope(XPS)were applied to characterized and identified the structure and properties of the Mn-oxidizing production of the Mn-oxidizing bacteria.The oxidation products were applied to the degradation of pesticides.The mainly results were listed as follows:1.The bacterial strains used were selected from heavy metal contaminated soil samples by the members of the same research team.The strain has strong ability of Mn oxidation.The strain was identified by16S r DNA,and the results showed that the strain belonged to the Providencia sp.2.The structure of purified the Mn-oxidizing production of soil bacteria LLDRA6 was characterized by SEM,XRD,HRTEM,N₂adsorption and XPS.The results present that the purified biogenic Mn oxide minerals are fine particles with a pore size of about 2-50 nm,which is a bixbyite with poorly-crystalline,and the specific surface area is5.7399 m²/g.XPS characterization results showed that the purified biogenic Mn oxides had three different valence states of element Mn,in which Mn³⁺was the main one.3.The degradation of three pesticides were studied in the co-existence system of soil bacteria LLDRA6 and biogenic Mn oxide.Four groups of experiments were set up,which were soil bacteria,the coexistence system of soil bacteria and unpurified biogenic Mn oxide,purified biogenic Mn oxide and the structure and properties of purified the Mn-oxidizing production of the of soil bacteria LLDRA6 was investigated using SEM,XRD,HRTEM,N₂ adsorption and XPS.coexistence system of soil bacteria and purified biogenic Mn oxide.Among them,the coexistence system of soil bacteria LLDRA6 and purified biogenic Mn oxide had the best degradation effect on the three pesticides.The degradation rates of atrazine on concentrations of 0.1,1and 10 mg/L were 55.00%,46.00%and 37.90%,respectively.The degradation rates of carbendazim on concentrations of 0.1,1 and 10 mg/L were 14.30%,6.80%and 1.53%,respectively.The degradation rates of bifenthrin on concentrations of 0.1,1 and 10 mg/L were 3.15%,0.53%and 0.047%,respectively.