Screening Of Aflatoxin B1 Degrading Bacteria And Optimization Of Culture Conditions

Aflatoxin B1（AFB1）is a mycotoxin,which is widespread in nature and has strong carcinogenicity and teratogenicity.Until now,there has been no safe and effective method to degrade AFB1.In this paper,the strains capable of efficiently degrading AFB1 was screened out in the grain,which provided a reliable solution for the future treatment of AFB1.Using moldy rice,corn,soybean,paddy,and peanuts as research objects,and using coumarin as a culture medium,purifying and culturing three times or more,screening of 36strains of bacterial growth that can use coumarin as the sole carbon source.Of the 36 strains of bacteria,9 strains were found to have a certain ability to degrade AFB1 after re-screening,of which 3 strains:HS-1,DZ,and HS had higher degradation rates of AFB1,which were 70.65%,61.42%and 46.63%.After microbiological and molecular biological identification,HS-1 and DZ can be identified as Bacillus subtilis,and HS as Bacillus safensis.By optimizing the single factor,the best degradation effect of three degrading bacteria on AFB1 was explored.After the temperature,pH,filling volume,inoculation volume,fermentation time,carbon source,nitrogen source,and metal ion environmental factor tests,it was found that HS-1 was at 37℃,pH 7.0,the filling volume was 50 ml,and the inoculation volume was 4%,fermentation time is 48 h,carbon source is glucose,nitrogen source is beef paste,Mg²⁺is metal ion,the degradation rate of AFB1 can be as high as76.65%,DZ at 37℃,pH 7.0,and the loading volume is 50 ml.The inoculation amount is6%,the fermentation time is 60 hours,the carbon source is glucose,the nitrogen source is beef paste,and Mg²⁺is metal ions,the degradation rate of AFB1 is 64.29%;HS at 37℃,pH8.0,loading volume is 100 ml,inoculation volume is 4%,fermentation time is 48 hours,carbon source is glucose,nitrogen source is beef paste,and Mg²⁺is metal ion,the degradation rate of AFB1 is increased to 47.35%.In order to further enhance the ability of strains to degrade AFB1,the degrading bacteria were combined in pairs to explore the ability of AFB1 to degrade under the optimal conditions after mixed culture of bacteria.The test results show that the degradation rate of AFB1 after the combination is significantly improved by 13%and more than before the optimization.Among them,HS-1 and DZ are in 9 different volume ratios,and the volume ratio is 2:1.The degradation rate of AFB1 is as high as 88.95%.The HPLC method was used to verify the test results based on the ELISA method.The difference between the detection results of the two methods is between 0.1-0.2.The results showed that the HPLC method was consistent with the ELISA method,which verified the accuracy of the test results.The strains that can efficiently degrade AFB1 are safe and effective,save time and effort,can save costs,and can be put in large quantities.The use of mixed strain cultivation methods in this paper also lays the foundation for the application of two strains in the future,and also degrades AFB1 provides a reliable solution.