Construction Of Shewanella Oneidensis MR-1@FeS Biohybrid Cells For Organic Pollutants Removal

In recent years,with the rapid development of industrial production in China,industrial wastewater containing a large amount of toxic and refractory organic pollutants has been discharged into the water environment.These organic pollutants,which are generally highly toxic to the human body and other organisms,are easily teratogenic,carcinogenic and mutagenic,and cause great damage to human health and ecological balance.Therefore,how to efficiently remove organic pollutants in water bodies is a crucial issue.Biological treatment has the advantages of mild reaction conditions,low cost,and not easy to cause secondary pollution,so it has received widespread attention.However,biological treatment also has the problem of low treatment efficiency.On the other hand,nano-Fe S（ferrous sulfide）is widely used in the reduction and removal of organic pollutants due to its excellent adsorption and reduction properties.However,the single use of nano-Fe S also has problems such as large consumption and prone to agglomeration.Therefore,this study combines the advantages of both microorganisms and Fe S nanomaterials to construct a new type of bio-nano hybrid cell with bioelectrochemical activity,which realizes the biosynthesis,in-situ assembly and in-situ regeneration of Fe S nanoparticles.On this basis,the removal performance of the hybrid system for organic pollutants was studied,and it was found that the hybrid system can use the biological electron transfer process to drive the Fe S nanoparticles to cyclically remove organic pollutants,which greatly improves the processing performance of the system and reduces the consumption of nanomaterials;further,this study preliminarily explains the mechanism of electron transfer and pollutant removal in the hybrid system.The research results of this paper are as follows:（1）A synthetic method of bio-nano hybrid system（Shewanella@ferrous sulfide（SW@Fe S））was established,and a hybrid cell with a uniform surface coating of nano-Fe S was constructed.Studies have found that SW can reduce extracellular Fe and S elements to synthesize Fe S nanoparticles.Through the optimization of the hybrid cell structure,it is found that when sodium thiosulfate is used as the sulfur source,the iron-sulfur concentration ratio is controlled at 1:2,the ratio of bacterial OD₆₀₀ and Fe S concentration is controlled at 1:1,nano-Fe S with a particle size of 20-50 nm can be synthesized,and the nano-Fe S can be more uniformly coated on the cell surface to form SW@Fe S hybrid cells with higher activity.（2）The electrochemical activity detection method of hybrid cells was established,and the bioelectrochemical performance of SW@Fe S hybrid cells was studied.Using a three-electrode system,a high-sensitivity electrochemical detection system for a hybrid system with fumaric acid as the electron acceptor,riboflavin as the electron mediator,and hybrid cells as the source of current signal was constructed.Studies on the electrochemical activity of heterozygous cells showed that SW@Fe S heterozygous cells can produce a more obvious high current response to separate addition of different concentrations of riboflavin and repeated addition of the same concentration of riboflavin.The current response is twice that of SW.Further studies have found that heterozygous cells can use riboflavin at a concentration as low as 1 n M for effective electron transfer,and the current response is linearly related to the concentration of riboflavin.The above results show that the hybrid cell has excellent electrochemical activity and high efficiency of electron transfer.（3）The removal performance of heterozygous cells for different organic pollutants was studied,and the electron transport mechanism was clarified.Studies have shown that the removal rate of organic pollutants by hybrid cells is significantly higher than that of pure bacteria or single bio-Fe S:the reduction rate of p-nitrophenol by the hybrid system can reach 0.083 h^-1,which is about 5.8 times that of SW and about 19.6 times that of a single bio-Fe S（SW@Fe S after sterilization）.The reduction rate of trypan blue by the hybrid system can reach 0.179 h^-1,which is about 6.4 times that of SW,and about14.2 times that of a single bio-Fe S（SW@Fe S after sterilization）.On the other hand,hybrid cells can achieve in-situ recycling of nano-Fe S.The hybrid cell consumes 22μM nano-Fe S and degrades 463.6μM p-nitrophenol.On average,1μM nano-Fe S degrades 21μM p-nitrophenol,which significantly improves the utilization efficiency of nano-Fe S.Further studies have shown that the main mechanism of the reduction of organic pollutants by hybrid cells is:SW produces electrons through intracellular metabolism,and the electrons are transferred to the biological nano-Fe S on the surface of the bacteria through a complex transmembrane electron transfer mechanism,thereby achieving efficient reduction of pollutants.Therefore,a method of constructing SW@Fe S heterozygous cells was established in this paper,which realized in situ assembly and in situ regeneration of ferrous sulfide（Fe S）on the cell surface;the heterozygous cells have electrochemical activity and realize the efficient removal of organic pollutants.Compared with traditional biological treatment and chemical catalysis methods,this study not only improves the treatment efficiency of microorganisms to organic pollutants,but also improves the utilization efficiency of nanomaterials,which has great application potential.In the following research,we can try to construct heterozygous cells from other types of cells and nanomaterials with stronger catalytic properties,so as to expand their application scope in the field of environment.