Study On The Characteristics Of Bacterial Co-culture To Synthesize Selenium Nanoparticles

In recent years,the biological synthesis of selenium nanoparticles(Se NPs)has caught the researchers'attention due to its low toxicity and mild reaction conditions.Co-culture refers to the mixed culture of some specific microorganisms under anaerobic or aerobic conditions under aseptic conditions.However,the current research on the reduction of Se O₃^2-and the synthesis of Se NPs by microorganisms is mainly concentrated in single bacteria and reactors.There are few relevant reports on the study of co-culture of reduction of Se O₃^2-and the synthesis of Se NPs.Based on the previous experiments,this study focuses on the above-mentioned problems,from the functional gene prediction of synthetic Se NPs,the characteristics of single strains and co-culture systems to synthesize Se NPs,and the preliminary application of Se NPs.The main contents are as follows:The Genbank database was used to analyze the genomes of Providencia sp.DCX(MF957299)and Alcaligenes sp.YBY(MF957298),and the possible functional genes for the synthesis of Se NPs were predicted.Aligning several protein sequences related to the reduction of,among them,there are 3 identical residues and 105 highly similar residues.These residues may be related to the reduction of Se O₃^2-.Comparing the proteins related to the Se O₃^2-reduction process in the literature with the proteomic data of strains DCX and YBY showed that there are similar protein sequences in strains DCX and YBY.Investigate and compare the characteristics of Se NPs synthesized by single strain and co-culture system.The original concentration and p H have important effects on the synthesis of Se NPs.The surface response method was used to optimize the conditions for the reduction of Se O₃^2-in the co-culture system.The optimal reaction conditions were:2.18 m M and p H6.83,and the highest reduction rate reached 97.09%.SEM showed that the morphology of Se NPs is spherical and pseudo-spherical.DLS analysis showed that the average particle size of Se NPs was 18.07 nm,with good dispersibility and good stability.XRD analysis proved that the crystal structure of Se NPs is hexagonal.FTIR analysis proved that functional groups such as amino group and carboxyl group participated in the Se O₃^2-reduction and stabilization process.Compared with a single strain,the co-culture system has better Se NPs synthesis ability and can tolerate higher concentrations of Se O₃^2-.XPS results showed that Se(II)is an intermediate product in the reaction process.The co-culture system still maintained a higher GSH content in the late growth period,which is more conducive to the reduction of Se O₃^2-.In order to explore the preliminary application of the synthesized Se NPs,an application experiment was carried out on the co-culture system synthesized Se NPs.The Se NPs synthesized by the co-culture system showed in antibacterial experiments that Se NPs have good biocompatibility,which is beneficial to their application in the environmental field.The adsorption kinetics of Se NPs on Congo red belongs to the pseudo-first-order model,and the adsorption kinetics of crystal violet belongs to the pseudo-second-order model.It shows that the absorption of dyes by Se NPs is a complicated process.