| Mycotoxins are commonly toxic secondary metabolites produced by fungi in feed,and zearalenone(ZEN)is one of several mycotoxins impairing the livestock industry.Due to the extensive pollution and toxicity of ZEN,it has always been a research hotspot to find effective detoxification methods of ZEN.Biological methods have the advantages that physical and chemical methods cannot replace,such as its specificity,mild reaction conditions and minimal nutritional damage,which attracte much attention.Some bacteria that can degrade zearalenone have been screened,but their degradation characteristics,the safety of the degradation products,and the effectiveness in animals need to be studied further.Therefore,we conducted the present experiment to screen a strain that can high-efficiently degrade zearalenone.Screening and identification of the bacteria degrading ZEN.By enrichment and domestication of bacteria from pig’s manure and detection of ZEN and its degradation products with HPLC,10 strains with degradation effect of zearalenone were screened out,and finally the highest degradation efficiency of the strain,ZJ-2019-1,was selected as its degradation rate of ZEN(10 mg/L)over 98% when fermented in LB liquid medium for 48 h.The ZJ-2019-1 strain was confirmed as Bacillus subtilis by morphology and 16 S r DNA gene sequence alignment.The degradation characteristics of strain ZJ-2019-1 to ZEN and the cytotoxicity of the degradation products.The way bacteria removing ZEN includes the adsorption of ZEN by their cell wall and the degradation of ZEN by its secreted active substances,and in the present study,the detoxification effect of strain ZJ 2019-1 is mainly by its extracellular enzymes.The detoxification of ZEN by strain ZJ 2019-1 could maintain a high degradation rate within 48 h,which was more than 95% in the 20 mg/LZEN(initial concentration),37℃(the optimum temperature)and p H 7.0(optimum p H value),and the ZEN degradation activity of the supernatant enzyme was affected by temperature,p H,ZEN concentration,EDTA concentration and metal ions.The degradation rate was the highest when the ZEN concentration was 10 mg/L,the temperature was at 37℃ and p H was 7.0;EDTA had obvious inhibitory effect on the enzyme;Fe3+ had the most obvious inhibitory effect,but Mn2+ had activated effect on the enzyme.The degradation products of the strain ZJ-2019-1 degrading ZEN had very low toxicity on MCF-7 cells and Hep G2 cells.In all,the strain ZJ-2019-1 was effective in degrading ZEN and was safe for animal feeding.we conducted the trial on gilts in three groups,the control group fed on basic diet,T1 group fed on ZEN-contaminated diet and T2 group fed on ZEN-contaminated diet adding ZJ-2019-1 bacterial solution,to investigate the effect of ZJ-2019-1 on performance,reproductive organs and hormones of gilts fed on ZEN-contaminated diet.It showed that the diet containing 970 μg/kg of ZEN had caused vulva swelling and increased the index of reproductive organs,affected the reproductive hormones concentration in the blood,increased the residual amount of ZEN and its metabolites in the body,damaged reproductive cells,and affected expression of estrogen receptor,but the strain ZJ-2019 added to diets contaminated by ZEN significantly alleviated the adverse symptoms.The experiment design was the same as the experiment 3.The content of ileum,colon and cecum were collected to investigate the effect of the strain ZJ-2019-1 on the gut microorganisms of the replacement gilts fed on the ZEN-contaminated diet.It showed that ZEN could significantly decrease the diversity of bacteria in the ileum with decreasing probiotics but increasing pathogenic bacteria in the gut.Adding ZJ-2019-1 to the ZEN-contaminated diet could alleviate the adverse effect of the ZEN without causing imbalance of the intestinal flora in the gilts.It was concluded that the Bacillus Subtilis ZJ-2019-1 had potential application prospects for detoxification of zearalenone in feed. |
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