Screening The Biocontrol Bacterium To Against Aspergillus Flavus And Identification The Antibacterial Lipopeptide Of Biocontrol Strain

Aspergillus flavus is an oridinary saprophytic fungi,which causes a lot of agricultural pollution.Peanuts,grains,nuts are more apt to Aspergillus infection.Some studies show that about 25%of the world’s food crops were contaminated by mycotoxins,so they could not be eaten and be wasted.It caused huge economic losses as much as billions of dollars.In addition,the fungus can also cause a serious threaten to the health of human.If someone exposure to the toxin long-term,it also improves the possibility to suffer from liver cancer.So,how to prevent A.flavusinfection and aflatoxin contamination effectively has very important significance.As people’s consciousness of environmental protection,the demand of health,using biological control to plant diseases has become a mainstrearm.30 strains with broad-spectrum antimicrobial activity from existing biocontrol strain library were selected to investigate how they affect the growth,toxin production of Aspergillus flavus and degregation of aflatoxin B,.The results indicated that 9 biocontrol strains had shown antagonism to Aspergillus flavus on PDA plate and the radius of inhibition zone was 0.58^3.25 mm.DS22 had the highest inhibition rate to prolong hyphae of A.flavus.When compared with the control,biocontrol strains could significantly inhibit mycelial dry weight of A.flavus.And biocontrol strains inhibited aflatoxin production in PDB.Among them,the inhibition rate of 24 biocontrol strains reached to 90%,the same as in PDB with peanut powder.Besides,17 biocontrol strains could reduce toxin pollution in peanut kernels.The inhibition rate was 15.12～66.08%.They could reduce about 49.82-217.72μg/kg toxin pollution in the peanut kernels compared with the control.It is the first report demonstrating that Serratia sp.,Enterobacter sp.and Pseudomonas sp.could reduce toxin pollution caused by A.flavus in peanut.The results still showed biocontrol strains could degregate aflatoxin B,and the degregation rate was 9.22%～68.91%.In summary,we supported some biocontrol strains(strain 54,1JN2,DS22,HS10 et al)had a greater biocontrol potential of prevention A.flavus and aflatoxin contamination.The fermentation supernatant of Bacillus pumilus DS22 had great inhibitory on the growth of A.flavus.HCl was used to precipitate the liquid culture of this strain,and mechanol was used to extract the precipitation.Then Sephadex LH-20 column was used to separate the crude extract.And finally the active ingredients were purificated by reverse phase high performance liquid chromatography(RP-HPLC).The results indicated that the substance could be C14-bacillomycin D-Ci 7-bacillomycin D.In summary,we have selected many strains had the ability to inhibit the growth of A.flavus and reduce aflatoxin of A.flavus.Then we explored the antibacterial substancesof strainDS22,and the results showed maybe something like C14-bacillomycin D-Ci 7-bacillomycin D played the role to inhibit growth of A.flavus.It will provide a resorce of strains against A.flavus,and a theoretical basis for properly taking advantage of DS22 and its antimicrobial substances in the future.