| Aflatoxin B1 is one of the most common mycotoxins, which is extremely toxic. The contamination of grain crops and feed by aflatoxin B1 causing huge economic losses to our country’s animal husbandry,threating humanbeing’s health.Therefore it is of vital importance to develop an efficient method to remove aflatoxin B1.Nowadays, because of its high efficiency, pollution-free, mild reaction conditions and not destroying products’ quality microbe solid-state fermentation attracts extensive attention. Cellulosimicrobium funkei is a bacterial strain which could remove AFB1 efficiently. based on the previous research, we did the following works:1 Presumed mechanism of Cellulosimicrobium funkei removing AFB1We prepare bacteria broth,extracellular extracts, protein extracts which obtained from 70% ammonium sulfate precipitation and supernatant, and to study the AFB1 removal ability of this four compositions respectively. extracellular extracts could remove 86.21%AFB1,which is close to bacteria broth(P>0.05), the AFB1 removal ratio of protein extracts was satisfying. Treating extracellular extracts by proteinase K and SDS, we study the possible AFB1 removal mechanism by heating extracellular extracts,changing p H of extracellular extracts, reextracting AFB1-extracellular extracts complex preliminary. The AFB1 removal ratio of extracellular extracts was decreased to 32.68% when treated with Proteinase K and 0.5% SDS mixture,as the concentration increasing, the AFB1 removal ratio rised linearly, extracellular extracts still had a high capacity to remove AFB1 under conditions of strong acid or strong alkaline, the AFB1 removal ratio of extracellular extracts could increase by 7.42% by heating, the AFB1 removal ratio of extracellular extracts could decrease by 6.63% by reextracting the AFB1-extracellular extracts complex. These results demonstrated that the removal effect of Cellulosimicrobium funkei on AFB1 resulted from combined action of protein and other active substances in extracellular extracts by adsorption mainly.2 The best technology for cottonseed meal solid-state fermentationWe Used the Cellulosimicrobium funkei to ferment the cottonseed meal with AFB1.Single factor experiment showed that the optimal ranges of fermentation temperature,fermentation duration,material-water ratio and inoculum size were 30 ℃,35 ℃,40 ℃;96 h,120 h,144 h;1:0.5,1:0.6,1:0.7;5%,10%,15% respectively. In order to optimize the fermentation conditions the orthogonal experiment was done Basing on thesingle factor experiment. AFB1 removal ratio, Dry matter loss ratio,organoleptic properties of fermented cottonseed meal were tested respectively.The optimal fermentation conditions such as fermentation temperature, fermentation duration,material-water ratio and inoculum size were 35 ℃,144 h,1:0.5,15% respectively. AFB1 removal ratio is more than 80% under the optimum conditions.3 Efficiency evaluation of fermented cottonseed meal in vivoone hundred and forty 5-day-old Cherry Valley ducks were randomly divided into five treatment groups with four replicates of seven birds each. Group I was the control group,the ducks in this group were fed on basal diet. The other four dietary treatments consisted of :groupⅡ, diet with 10% of soybean meal replaced by AFB1 contaminated cottonseed meal;groupⅢ: diet with 10% of soybean meal replaced by 2.5% fermented cottonseed meal+7.5% AFB1 contaminated cottonseed meal;groupⅣ, diet with 10% of soybean meal replaced by 5% fermented cottonseed meal+5% AFB1 contaminated cottonseed meal;group Ⅴ, diet with 10% of soybean meal replaced by fermented cottonseed meal. Every day the ducks of each group were fed twice for 14 days running. Ducks were monitored daily,body weight and feed consumption were recorded.At the seventh day and fourteenth day,two ducks was chosen from every replicate randomly to be slaughtered, data of relative organs weight and blood samples were collected. The result showed as follow:Campared to the control group, the F/G of the groupⅡ’s ducks were signifigantly increased(P<0.05),relative weights of liver,kidney and spleen were signifigantly increased(P<0.05),while bursa of fabricius’ s relative weights was signifigantly decreased(P<0.05). AST,ALT,BUN,Cr in serum were signifigantly increased(P<0.05), the amount of TP and ALB in serum were signifigantly decreased(P<0.05).The amount of WBC,LYM,RBC,HGB,HCT,MCH,MCHC in blood were signifigantly decreased(P<0.05), the amount of MCV,RDW were signifigantly increased(P<0.05).The lesions in liver of groupⅡ’s ducks included necrosis and hemorrhage,fibrosis,regeneration of nodules,bile duct proliferation/hyperplasia,vacuolation and fatty infiltration enlarged hepatic cells. Campared to the groupⅡ,as the proportion of fermented cottonseed meal increased in diets, F/G showed a slow downward trend to the level of the control group, relative weights of liver,kidney and spleen were gradually decreased, bursa of fabricius’ s relative weights was gradually increased to the level of the control group.Also, The amount ofAST,ALT,BUN,Cr in serum were gradually decreased,the amount of TP and ALB in serum were gradually increased.Approaching to the control group,the amount of WBC,LYM,RBC, HGB,HCT,MCH, MCHC in blood were gradually increased, the amount of MCV,RDW were gradually decreased approaching to the control group.These results showed that solid-state fermentation can reduced the concentration of AFB1 in cottonseed meal, thus relieving the descending production performance, immunosuppression, injury of liver and kidney, anemia by AFB1 at a certain extent.Conclusion: Cellulosimicrobium funkei could remove AFB1 efficiently. The AFB1 removal mechanism of this stain may be the combined action by protein and other active substances in extracellular extracts by adsorption.The optimum conditions of cottonseed meal fermentation in solid-state were confirmed: fermentation temperature was35 ℃, fermentation duration was144 h,material-water ratio was 1:0.5 and inoculum size was 15%.AFB1 removal ratio could be more than 80% under these conditions.The vivo test showed that :removing AFB1 by fermentation in solid-state in the optimum conditions could relieve negative effects on the production performance, the injury of liver and kidney, hematopoietic function, Immunosuppression. |
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