Study On Biosynthesis And Antifungal Activity Of Nano-Selenium

Selenium(Se)is an essential trace element for animals and humans,and thus,low dietary intake of Se can cause health disorders in humans and animals.It has important biological effects and has preventive and therapeutic effects on some diseases.However,the range of biological activity of selenium is relatively narrow,so it is easy to stray into the toxicity range of selenium when it is applied.High concentrations of selenium are highly toxic and it can pollute the environment.The low concentration of selenium has many health effects on life,and nano-selenium has the advantages of more efficient and high safety for organisms.The application of nanomaterials in the agricultural field is increasingly widespread.However,the commonly used physical and chemical synthesis methods have problems such as high cost and large pollution to environment.Therefore,the new green synthesis technology for preparing nanomaterials using the biological reduction method has became one of the hot topics in the field of nanomaterials research.In this research,the bioactive bacteria Bacillus subtilis and sodium selenite were separately incubated and incubated in the laboratory.Then the SEM-EDS combined characterization test was performed on the fermentation product to verify that the biocontrol bacteria Bacillus subtilis can selenium The reduction of sodium into elemental nano-selenium;the final study of the synthesis of elemental nano-selenium on the mycelial growth,spore germination of plant pathogenic bacteria Magnaporthe oryzae and the incidence of inoculation of live rice blast.The main findings are as follows:(1)In this research,sodium selenite was reduced by the biocontrol bacteria Bacillus subtilis.Under the condition of 4mM sodium selenite,the reduction efficiency was 48.69%.The reduction product of sodium selenite was subjected to field scanning electron microscopy(SEM)and energy analysis spectrometer(EDS)characterization test.It was found that the biocontrol bacteria Bacillus subtilis can reduce sodium selenite into nanosized elemental selenium.The diameter size is basically distributed in the range of 50-250 nm.In addition,after the fermentation product was allowed to stand at room temperature for four weeks and sterilized by moist heat,the SEM-EDS was used for the characterization test.The spherical particles in the sample were still nano-sized,and the red liquid was still observed with the naked eye.This proves that the biosynthesized nano-selenium is relatively stable and difficult to change.(2)Preparation of elemental nano-selenium by reduction of sodium selenite using biocontrol bacteria Bacillus subtilis.The effects of different concentrations of nano-selenium on the mycelia growth and spore germination of the plant pathogen Magnaporthe grisea were studied:control group,0 ?g/ml;treatment group 50-250?g/ml,each 50 ?g/ml was a concentration gradient.The data analysis showed that the virulence regression equation for the effect of nano-selenium on mycelial growth of Magnaporthe oryzae was:y=2.7306+1.5095x;correlation coefficient(r)value was 0.9308;EC50 was 31.8707?g/ml;EC90 was 225.0985?g/ml.The virulence regression equation for the effect of nano-selenium on spore germination of Magnaporthe oryzae was:y=1.2465+1.5290x;correlation coefficient(r)value was 0.9244;EC50 was 285.0339?g/ml;and EC90 was 1963.648?g/ml.In addition,the live inoculation test of rice blast fungus was performed in five groups:control group,1.96mg/ml nano-selenium treatment group,biocontrol bacteria Bacillus subtilis treatment group,1 mM sodium selenite solution treatment group,Bacillus subtilis treatment,3d After sodium selenite solution treatment group,sodium selenite solution treatment,3d after the Bacillus subtilis treatment group,research and analysis of its impact on the incidence of rice blast.Studies have shown that after 7 days,except for the normal incidence of rice blast in the control group,no treatment group had any disease.Therefore,preliminary conclusions are drawn that nano-selenium has a certain prevention and control effect on rice blast.