Study On Biodegradation Of Aflatoxin B1 By Rhodococcus Opacus PD630

Aflatoxin B1?AFB1?is a dihydrofuran coumarin derivative mainly produced by Aspergillus flavus and Aspergillus parasiticus.AFB1 is widely contaminated in grains,nuts,fruits and spices.AFB1 has strong hepatotoxicity,carcinogenicity,mutagenicity,immunosuppression and growth suppression effects on humans and animals.AFB1 is the widest pollution and the most harmful mycotoxin.In the study on the degradation of AFB1,the microbial degradation method has become a research hotspot in the field of degradation due to its advantages of strong specificity,environmental friendliness and mild operating conditions.In this study,a microbial strain which can efficiently degrade AFB1 was screened out.The degradation conditions of AFB1 by this strain were studied,and the degradation mechanism was preliminarily analyzed.Finally,the application experiment was carried out.The contents and results of this paper are as follows:?1?Screening of AFB1 degrading bacteria and study on degradation conditions:Through co-cultivation of the strains and AFB1,a strain of Rhodococcus opacus PD630 strain that can efficiently degrade AFB1 was selected from the strain library.After 72 h,the degradation rate of AFB1 was as high as 93.04%.The PD630 strain has no inhibitory effect on the main AFB1producing fungi,namely A.flavus and A.parasiticus.The degradation activity of the strain is closely related to the concentration of AFB1 in the medium,it can maintain high degradation activity?>66%?in the pollution range of 0-2?g/m L.Using glucose and mannitol as carbon source or tryptone and urea as nitrogen source in culture medium can enhance the degradation activity of AFB1.After AFB1 induced activation,the degradation efficiency of PD630 strain was significantly improved,and the degradation time was shortened from 48 h to 24 h.?2?Preliminary study on AFB1 degradation mechanism of R.opacus PD630:The degradation activity of PD630 strain extracellular supernatant on AFB1 was significantly higher than bacterial suspension and intracellular lysate?P<0.05?.The active components of the extracellular supernatant were analyzed as thermostable enzymes through changes in degradation activity after treatment with proteinase k and heat.The extracellular crude enzyme solution precipitated with 70%saturation ammonium sulfate had the highest degradation activity,with a degradation rate of 55.01%.The extracellular crude enzyme solution can maintain high degradation activity of AFB1 in the range of p H 5-10 and temperature 10-80?.Li⁺and Cu²⁺are the main activators of enzymes.Through TLC and HPLC,it was found that AFB1 was completely degraded and the fluorescence disappeared,but the reported degradation products and degradation pathways were not found by LC-MS.?3?Application study on degradation of AFB1 by R.opacus PD630.In the three polluted substrates of maize,wheat and peanut,AFB1 content could be significantly reduced after solid-state fermentation for 72 h?P<0.05?,and the degradation rates were 64.17%,67.66%and 56.45%respectively.When the material-liquid ratio in maize and wheat is 1:1 and that in peanut is 1:1.4,the degradation activity to AFB1 is the highest.When the inoculation amount of PD630 strain was 20%,the degradation rate of AFB1 in maize,wheat and peanut reached the highest value.The temperature has little effect on the degradation activity of AFB1 in the three substrates,and the stable degradation activity can be maintained at the fermentation temperature of 20?-40?.In addition to the degradation of AFB1 by the PD630 strain,the degradation rates of ZEN in NB medium and maize were 55.65%and 40.12%,respectively.The degradation activity of DON is low,and the degradation rates in NB medium and corn are 22.49%and 18.44%,respectively.Through the above research,a microbial strain that can efficiently degrade AFB1 was selected.A method for strains to increase the degradation rate of AFB1 in contaminated medium and grains was established.The thermostable crude extracellular enzyme solution with degradation effect is obtained.It provides new strain resources for efficient degradation of AFB1,and also provides new methods for eliminating AFB1 pollution in food and feed.