Study Of Aflatoxin Degradation By Pleurotus Ostrcatiis

Aflatoxins are kind of carcinogenic, teratogenic and mutagenic toxic fungal secondary metabolites,and aflatoxin B1which is designated the most toxic by the World Health Organization cancer researchinstitutions. Aflatoxins are widely found in peanuts, corn and other crops. Aflatoxins not only have greatharm to human and animal health, but also have caused enormous loss to China’s export trade. The aimof this study is to get fungus strains which can degrade aflatoxins effectively.In this research, AFB1is extracted by and improved solvent extraction method and detected byAFB1ELISA test kit. The recoveries of AFB1in the react system are94.88%and93.04%when the totalamount of AFB1is500ng and1000ng. The relative standard deviations are less than5%. Therefore,extracting AFB1by improved solvent extraction method and detecting AFB1by AFB1ELISA test kit areavailable.In this study, five high laccase-production strains are selected by guaiacol selected medium plates(GLDS) and α-naphthol selected medium plates (NLDS) from eight Pleurotus ostreatus strainsaccording to the growth, the size of color ring, color depth and other features on the select plates. Twohigh laccase-production strains of the five Pleurotus ostreatus strains are selected by determininglaccase activity in liquid MSM medium which are Pleurotus ostreatus P1and Pleurotus ostreatus P2.The best strain of AFB1-degradation is Pleurotus ostreatus P1and the amount of AFB1-degradation is700.89ng by790μL Pleurotus ostreatus fermentation. The ability of AFB1-degradation increased whenthe laccase activity increased and decreased when the laccase activity decreased. In this study, laccaseactivity disappeared when Pleurotus ostreatus P1fermentation boiled15minutes. The rate ofAFB1-degradation was from75.82%to0.53%by790μL Pleurotus ostreatus P1fermentation and thetotal amount of AFB1was1000ng.The culture conditions of Pleurotus ostreatus P1were studied. Optimized conditions were asfollows: the culture medium was MSM medium and the pH of MSM medium was6.0, incubationtemperature was30°C, incubation speed was200rpm. Under the Optimized conditions, the rate ofAFB1-degradation was82.43%and the total AFB1-degradation was824.32ng in1000ng AFB1by790μL Pleurotus ostreatus P1fermentation.Incubation speed of Pleurotus ostreatus P1fermentation and AFB1was studied and there is nosignificant difference between the conditions of incubation temperature30°C and time72hours with noincubation speed or200rpm. The rates of1000ng AFB1degradation were76.13%and76.26%.Incubation time on the ability of AFB1-degradation was also studied. Incubation3days is a turningpoint in the degradation of AFB1and the rate of AFB1-degradation is from28.58%to75.82%whenincubated from2days to3days and the degradation rate can be91.80%when incubated8days. Theability of AFB1-degradation was higher when the incubation temperature was lower, but there is nosignificant difference between25℃and30℃. Pleurotus ostreatus P1fermentation also can have the ability of AFT-degradation and AFM1-degradation. AFT was completely disappeared and two new substances were found afterAFT-degradation according to the HPLC analysis spectra after950μL Pleurotus ostreatus P1fermentation and50μL AFT (AFB11μg/mL, AFB23μg/mL, AFG11μg/mL, AFG23μg/mL) incubation.The degradation rate of AFM1was88.36%according to the HPLC analysis spectra.