Screening Of Aflatoxin B₁ Removing Strain And Research Of Its Characteristics And Application

Aflatoxin B₁(AFB₁)is a mycotoxin widely found in nuts,peanuts,and most grains.It is classified by the World Health Organization as a Class IA carcinogen.AFB₁poses a huge threat to human health and the world economy,therefore,how to remove aflatoxin B₁economically and efficiently is an issue of global concern.Biological methods have been widely concerned for their lower cost,higher efficiency and safety.In this study,the strains that efficiently adsorb AFB₁were screened and initially identified.The growth conditions were optimized,and the adsorption mechanism and characteristics were studied;at the same time,a strain that produces laccase to efficiently degrade AFB₁was screened,and its degradation mechanism and characteristics were studied.Finally,their practicability and safety were systematically evaluated.The findings are as follows:(1)Taking the adsorption rate of AFB₁as the screening index,D1,a strain with high-efficiency AFB₁adsorption,was screened from fermented food and initially identified as Saccharomyces cerevisiae.It was found that the adsorption rate of D1 on AFB₁was positively correlated with its OD₆₀₀.The growth conditions were simply optimized,and the adsorption rate of 100?g/L AFB₁could reach 70.25%.(2)The adsorption effect of D1 on AFB₁was a reversible physical adsorption based on its cell wall polysaccharides.AFB₁existed on the surface of D1,and its structure and property remained unchanged.Heating and hydrochloric acid treatment could change the cell wall structure of D1 to a certain extent,and then the adsorption rate was increased.After the adsorption conditions were optimized,the adsorption rate of D1 heated at 100?for 30 min to AFB₁(100?g/L)could reach 89.97%,and it was 75.78%for AFB₁(1 mg/L).(3)Simultaneously,using the coumarin-guaiacol screening plate,a pleurotus eryngii that could produce laccase and efficiently degrade AFB₁was screened.Through gradient ammonium sulfate precipitation,it was preliminarily determined that the AFB₁degradation activity of crude enzyme solution was positively correlated with its laccase activity.The best conditions of pleurotus eryngii crude enzyme solution to degrade AFB₁were as follows:the reaction time was 5 d,the p H was 7.0,the temperature was 43?,and the concentration of Cu²⁺was 10 m M.(4)The mixed adsorption of yeast strains had no significant effect on the adsorption rate of AFB₁.And the combined adsorption of montmorillonite and D1 could increase the adsorption rate of AFB₁to 94.08%.Combined detoxification of adsorbed strain and crude enzyme solution could accelerate the process of detoxification.The adsorption rate could reach over 90%by secondary combined adsorption of D1(10~9CFU/m L)mixed montmorillonite(3.0 mg/m L)in liquid food.The best solid-liquid ratio of corn meal treated with D1 and crude enzyme solution was 1:2,and the detoxification rate of AFB₁could reach76.48%in 3 days.(5)The adsorption effect of D1 on AFB₁had no obvious change after freeze-drying.In artificial stomach and intestinal juice,the adsorption capacity of D1 after heat treatment remained unchanged.D1,fruiting body of Pleurotus eryngii and crude enzyme solution had no obvious inhibitory effect on the growth of Aspergillus flavus.AFB₁(10 mg/kg)caused very obvious physiological damage to red zebrafish,and the antioxidant index of its viscera was extremely significantly reduced.Adding cell wall extract of yeast D1 could improve this toxic damage,increase the survival rate and antioxidant capacity of red zebrafish.The product of AFB₁degraded by crude enzyme solution had no obvious oxidative damage to the viscera of red zebrafish,so the degradation reduced the toxicity of AFB₁.