The Screening Of Strains For Aflatoxin B₁ Degradation And The Detoxification Effects Of The Strains On Aflatoxin B₁

Aflatoxin is one of the most common mycotoxins, which is extremely toxin. The contamination of grain crops and feed by aflatoxin causing huge economic losses to our country’s animal husbandry. Therefore,it is of vital importance to stduy the means of detoxification. Biological degradation because of its efficient, pollution-free, and mild reaction conditions becomes a new research direction of aflatoxin detoxification. This research mainly includes the following aspects:1 Screening and identification for AFB1 degradation microbesUsing cumarin as the carbon source, eleven AFB1 degradation strains were selected from soils that polluted with polycyclic aromatic hydrocarbons,of which T3-5 strain was considered as the most efficient degrading strains with the degradation ratio of 94.16%.The T3-5 strain was identified as Cellulosimicrobium funkei with respest to its colony morphology, physiological and biochemistry characteristics and 16SrDNA sequence.2 The degradation mechanism of Cellulosimicrobium funkei for AFB1 and its opitimal condition for in vitro detoxificationPrepare extracellular extracts, cell suspension, intracellular extracts’respectively to study the ability to remove AFB1.AFB1 was effectively degraded by extracellular extracts of T3-5 strain with the degradation ratio of 94.16%. The mainly active substance was insensitivity to heat. The degradation ratio of extracellular extracts was decreased to 42.19% when treated with Proteinase K and 0.5% SDS mixture.While the AFB1 degradation ratio of protein extracts obtained from 70% ammonium sulfate precipitation was 53.61%.These results demonstrated that the degradative effect of Cellulosimicrobium funkei on AFB1 resulting from combined action of enzymes and other active substances in extracellular extracts.The optimal conditions of AFB1 degradation were obtained as follows:temperature 35℃; pH 6.5; fermentation time 18 h; degradation time 72 h.When the content of AFB1 is 1μg,0.5 mL extracellular extracts can reached the maximum degradation ratio.3 Satety assessment of Cellulosimicrobium funkei in vivosixty 4-day-old Cherry Valley commercial ducks are randomly divided into three treatment groups with four replicates of five birds each.The ducks in all groups were fed ordinary diets.From group I to group III, ducks were administered intragastrically with:1 mL LB medium;1 mL T₃-5 inoculum（1×10⁸ cfu/mL）; 1 mL T₃-5 inoculum（1x101¹0 cfu/mL）.Every day each group was gavaged one time and duckings were gavaged for 7 days running.At the seventh day and fourteenth day,one duck was taken out from every replicate randomly,and jugular bloodletting to dealth.The results showed that:T3-5 strain had no effect on ADG and ADFI,but could decreased F/G（P<0.05）. There were no different effect on serum AST、 ALT、 TP、 ALB and UN among all treated groups（P>0.05）. T3-5 strain could signifigantly decreased the E.coli count（P<0.05）.There were no significant differences on other microorganism indicators（P>0.05）.The duck’s liver didn’t be hurt if gavaged with 1×10⁸ cfu T₃-5 inoculum.4 Efficiency Evaluation of AFB1 degradation strain in vivosixty 4-day-old CherryValley commercial ducks are randomly divided into three treatment groups with four replicates of five birds each. The ducks in all groups were fed ordinary diets.From group â…  to group â…¢, ducks were administered intragastrically with:1 mL LB medium; 0.1 mg/kg·BW of AFB1 solution+1 mL LB medium; 0.1 mg/kg·BW of AFB1 solution+1mL T₃-5 inoculum（1x10⁸ cfu/mL）.Every day each group was gavaged one time and duckings were gavaged for 14 days running.At the seventh day and fourteenth day,one duck was taken out from every replicate randomly,and jugular bloodletting to dealth.The results showed that campared to the control, the ADG of the ducks that gavaged with AFB1 were signifigantly decreased（P<0.05）,while ADFI were signifigantly increased.Also,the contain of AST,ALT and UN in serum and E.coli count in cecum were signifigantly increased （P<0.05）,TP and ALB in serum and lactic acid bacillus count in cecum were signifigantly decreased（P<0.05）.For the ducks that gavaged with AFB1, supplemented with T3-5 inoculum had no effect on ADFI,showed a trend of increase ADG（P>0.05）,could signifigantly decreased F/G（P<0.05）.Also,supplemented with T₃-5 could signifigantly decreased the enzymatic activity of AST and ALT in serum （P<0.05）,and decreased E.coli and total aerobe bacteria count （P<0.05）, showed a trend of increase lactic acid bacillus count in cecum （P>0.05）. The liver cell was generalized swelling,apomorphosis and necrosis and the bile ducts was hyperplasiaed intense in the ducks that gavaged with AFB1,however, supplemented with T3-5 could relieve the injury obviously if ducks were gavaged with AFB1 last one week. T3-5 could not be relieve the injury of liver if ducks were gavaged with AFB1 last two weeks.Conclusion:Cellulosimicrobium funkei T3-5 that screed by this study could degradate AFB1 high performancely. The degradation mechanism of this stain may be the combined action of enzymes and other active substances in extracellular extracts.The vivo test showed that:T3-5 could improve growth performance and have no damage to duck’s kidney and liver if gavaged with 1×108 cfu T3-5 inoculum.The strain had tolerance to the environment of gastrointestinal tract,but couldn’t set in intestinal tract. The strain could decrease E.coli count in cecum and alleviate the descent of growth performance and liver damage which were originated by AFB1.Moreover,The strain made intestinal environment tended to be normal.