The influence of divalent cations and chelators on aflatoxin B1 degradation by Flavobacterium aurantiacum

The influence of divalent cations (Mg2+ and Ca2+) and chelators (EDTA and 1,10-phenanthroline) on aflatoxin B1 (AFB1) degradation by Flavobacterium aurantiacum was determined in an effort to elucidate the possible manner by which this organism degrades AFB1. AFB1 (10 microg/ml) was added to 72-h cultures of F. aurantiacum that had been washed and resuspended in phosphate buffer (pH 7.0). High-performance liquid chromatography was used to determine AFB1 concentration in these cultures. Incubating cells with 0.1, 1, and 10 mM Ca2+ for 48 h significantly increased AFB1 degradation by 11.8, 13.5, and 14.0%, respectively, compared with F. aurantiacum cells alone. Likewise, incubation with 0.1, 1, and 10 mM Mg2+ for 48 h significantly increased AFB1 degradation by 13.8, 13.3, and 13.1%, respectively. Incubating the bacterium with either divalent cation for 16 and 24 h did not significantly affect AFB1 degradation (P < or = 0.05). Addition of 0.1, 1, and 10 mM EDTA and 0.1 and 1 mM 1,10-phenanthroline resulted in significant increases in AFB1 degradation after 24 h. Significantly less AFB1 degradation was observed using 10 mM 1,10-phenanthroline after 24-h incubation. These results suggest the involvement of Mg2+ and Ca2+ cations in AFB1 degradation by F. aurantiacum.     

Degradation of aflatoxin B(1) by cell-free extracts of Rhodococcus erythropolis and Mycobacterium fluoranthenivorans sp. nov. DSM44556(T)

Biological degradation of aflatoxin B(1) (AFB(1)) by Rhodococcus erythropolis was examined in liquid cultures and in cell-free extracts. Dramatic reduction of AFB(1) was observed during incubation in the presence of R. erythropolis cells (17% residual AFB(1) after 48 h and only 3-6% residual AFB(1) after 72 h). Cell-free extracts of four bacterial strains, R. erythropolis DSM 14,303, Nocardia corynebacterioides DSM 12,676, N. corynebacterioides DSM 20,151, and Mycobacterium fluoranthenivorans sp. nov. DSM 44,556(T) were produced by disrupting cells in a French pressure cell. The ability of crude cell-free extracts to degrade AFB(1) was studied under different incubation conditions. Aflatoxin B(1) was effectively degraded by cell free extracts of all four bacterial strains. N. corynebacterioides DSM 12,676 (formerly erroneously classified as Flavobacterium aurantiacum) showed the lowest degradation ability (60%) after 24 h, while >90% degradation was observed with N. corynebacterioides DSM 20,151 over the same time. R. erythropolis and M. fluoranthenivorans sp. nov. DSM 44,556(T) have shown more than 90% degradation of AFB(1) within 4 h at 30 degrees C, whilst after 8 h AFB(1) was practicably not detectable. The high degradation rate and wide temperature range for degradation by R. erythropolis DSM 14,303 and M. fluoranthenivorans sp. nov. DSM 44,556(T) indicate potential for application in food and feed processing.     

Biotransformation of Isoflavones by Bifidobacteria in Fermented Soymilk Supplemented with D-Glucose and L-Cysteine

ABSTRACT: Soymilk prepared using soy-protein isolate supplemented with D-glucose and L-cysteine was fermented with 4 strains of Bifidobacterium. Enumeration of bifidobacteria and quantification of isoflavones using HPLC were performed at 0, 12, 24, 36, and 48 h of incubation. Supplementation did not significantly enhance ( p > 0.05) the growth of bifidobacteria between 0 and 12 h, but did after 12 h. The increase in concentration of isoflavone aglycones and equol was significantly lower ( p < 0.05) in supplemented soymilk after 24 h when compared to plain soymilk. Supplementation increased the concentration of aglycones by 0.796 mg/100 mL in soymilk fermented with B. animalis between 12 and 24 h, and the population by 1.27 log₁₀ CFU/mL ( p < 0.05).     

Effects of nitrate or nitro supplementation, with or without added chlorate, on Salmonella enterica serovar Typhimurium and Escherichia coli in swine feces

The effects of coincubating the active agent of an experimental chlorate product with nitrate or select nitro compounds, possible inducers and competing substrates for the targeted respiratory nitrate reductase, on concentrations of experimentally inoculated Salmonella enterica serovar Typhimurium and indigenous Escherichia coli were determined. Studies were completed in swine fecal suspensions as a prelude to the administration of these inhibitors to pigs. Results confirmed the bactericidal effect of chlorate (5 to 10 mM) against these fecal enterobacteria, reducing (P < 0.05) concentrations by > 2 log CFU ml(-1) after 3 to 6 h of incubation. An effect (P < 0.05) of pH was observed, with considerable regrowth of Salmonella and E. coli occurring after 24 h of incubation in suspensions buffered to pH 7.1 but not in suspensions buffered to pH 6.5 or 5.6. A 24-h coincubation of fecal suspensions with 5 to 10 mM chlorate and as little as 2.5 mM nitrate or 10 to 20 mM 2-nitro-1-propanol, 2-nitroethanol, and, sometimes, nitroethane decreased (P < 0.05) Salmonella but not necessarily E. coli concentrations. 2-Nitro-1-propanol and 2-nitroethanol exhibited inhibitory activity against Salmonella and E. coli by an undetermined mechanism, even in the absence of added chlorate.     

Influence of processing schemes on indicative bacteria and quality of fresh aquacultured catfish fillets.

Fresh aquacultured catfish fillets were obtained from three processors using different processing protocols in summer, autumn, winter, and spring and evaluated for microbial quality. Twenty freshly processed fillets were randomly selected and each fillet was placed in a sterile polyethylene bag. The fillets were transported on ice-pack overnight by air immediately after processing. Five fillets were randomly selected for microbial assays. Each fillet was weighed and an equal volume of sterile 0.1% peptone water at 0 to 1 degrees C was added aseptically. The fillet was massaged (or rinsed) for 120 s and the rinse was used to determine microbial quality. Aerobes (incubation at 35 degrees C for 48 h) and psychrotrophs (incubation at 20 degrees C for 96 h) were enumerated using 3M Petrifilm Aerobic Count plates. Escherichia coli (incubation at 35 degrees C for 24 to 48 h) and total coliforms (incubation at 35 degrees C for 24 to 48 h) were enumerated on 3M Petrifilm E. coli Count plates. Staphylococcus aureus counts were determined on Baird-Parker agar (incubation at 35 degrees C for 48 h). Significant differences (P < or = 0.05) in aerobic, psychrotrophic, total coliform, E. coli, and S. aureus counts due to temperature effects during production and variations in processing protocols were observed. E. coli and S. aureus counts were significantly different during the four seasons. E. coli and S. aureus counts were high during summer and low during winter weather. There was a significant difference (P < or = 0.05) in aerobic, psychrotrophic, and total coliform counts among the three processors during warm weather; however, these differences were significantly (P < or = 0.05) reduced in cold weather.     

中性蛋白酶降解棉粕中棉酚的研究

该实验旨在利用芽孢杆菌（Bacillus）和乳酸杆菌（Lactobacillus）发酵棉粕,研究对棉粕中游离棉酚降解率及饲料活菌数的影响。研究发现,芽孢杆菌BLCC1-0039在37 ℃发酵24 h后棉酚降解率达到85.89% （P＜0.05）,产中性蛋白酶活性达到2 811.40 U/g发酵料（P＜0.05）;发酵48 h时棉酚降解率达到91.47%,产中性蛋白酶活性达到2303.24 U/g。单独添加中性蛋白酶发酵24 h时,添加量为1 000 U/g的棉酚降解率已达到58.46%,2 000 U/g时棉酚降解率达到72.68%;发酵48 h时1 000 U/g的棉酚降解率已达到73.29%。乳酸菌发酵棉粕不能降解棉酚,但乳酸杆菌BLCC2-0092添加1 000 U/g的中性蛋白酶发酵24 h时,棉酚降解率达到67.13%,pH值降至4.71。     

施氏假单胞菌F4对黄曲霉毒素B_1的酶解作用及其降解产物的初步分析

施氏假单胞菌F4能高效降解黄曲霉毒素B1(aflatoxin B1,AFB1)。研究了F4的AFB1降解活性、降解动力学以及蛋白酶K和SDS对其降解性能的影响。F4细胞悬液与毒素共培养72 h后降解率达80.03%;蛋白酶K处理对降解率没有影响,SDS处理的细胞悬液基本丧失了降解活性。不同时间点的降解液上清液仍能有效降解残留AFB1,其中以60 h的降解液上清液活性较好,与残留AFB1继续作用48 h后降解率达84.30%;而经蛋白酶K处理后降解率仅为45.42%。低浓度AFB1诱导对菌体的降解活性没有影响。上述结果提示,F4通过胞内酶作用降解AFB1。高效液相色谱对产物分析表明,F4可将AFB1酶解为至少2种产物。     

Preliminary evidence that degradation of aflatoxin B1 by Flavobacterium aurantiacum is enzymatic

The ability of crude protein extracts from Flavobacterium aurantiacum to degrade aflatoxin B1 (AB1) in aqueous solution was evaluated. Crude protein extracts (800 microg of total protein per ml) degraded 74.5% of AB1 in solution. An average of 94.5% of AB1 was recovered after incubation with heat-treated crude protein extracts (800 microg of total protein per ml). DNase I-treated crude protein extracts degraded 80.5% of AB1 in solution, suggesting that removal of aflatoxin by F. aurantiacum is not due to nonspecific binding with the bacterium's genomic DNA. Proteinase K-treated crude protein extracts degraded 34.5% of AB1, providing evidence that degradation of aflatoxin is linked to a protein that is possibly an enzyme. Solution pH affected the amount of AB1 degraded by crude protein extracts after 24 h. Maximum degradation was observed at pH 7 (pH levels tested: 5, 6, 7, and 8), with some AB1 degradation occurring at pH levels as low as 5 and as high as 8. Acidic pH levels were more detrimental to the ability of crude protein extracts to degrade AB1 than was basic pH. The results of this work indicate that the degradation of AB1 by F. aurantiacum may be enzymatic.     

复合菌系降解黄曲霉毒素B_1的效果及组成多样性研究

采用"外淘汰法"筛选了一组对黄曲霉毒素B_1(aflatoxin B_1,AFB_1)具有高效降解能力的复合菌系FBAD-2,该复合菌系在120 h内能将质量浓度为2 000μg/L的AFB_1完全降解,对质量浓度为5 000μg/L的AFB_1能降解90%。FBAD-2在30~70℃的范围内均能保持对AFB_1的高效降解能力,其最适温度为60℃。毒素降解实验分析表明,FBAD-2对AFB_1的降解主要是胞外酶的作用,其最适产酶时间为24 h,此时的胞外粗酶液在48 h内能将5 000μg/L的AFB_1完全降解。16S rDNA基因组测序分析结果表明,FBAD-2的微生物组成主要包括土芽孢杆菌(Geobacillus)、嗜热小杆菌(Symbiobacterium thermopilum)、梭菌(Clostridium)和热厌氧杆菌(Tepidanaerobacter)等。     

Inactivation of Enterobacter sakazakii in reconstituted infant formula by monocaprylin

Enterobacter sakazakii is an emerging pathogen that causes meningitis, bacteremia, sepsis, and necrotizing enterocolitis in neonates and children, with a mortality rate of 14%. Epidemiological studies have implicated dried infant formula as the principal source of the pathogen. Caprylic acid is a natural eight-carbon fatty acid present in breast milk and bovine milk and is approved as generally recognizable as safe by the U.S. Food and Drug Administration. The objective of this study was to determine the antibacterial effect of monocaprylin (monoglyceride ester of caprylic acid) on E. sakazakii in reconstituted infant formula. A five-strain mixture of E. sakazakii was inoculated into 10-ml samples of reconstituted infant formula (at 6.0 log CFU/ml) followed by 0, 25, or 50 mM (1%) monocaprylin. The samples were incubated at 37 or 23 degrees C for 0, 1, 6, and 24 h and at 8 or 4 degrees C for 0, 6, 24, and 48 h, and the surviving populations of E. sakazakii at each sampling time were counted. The treatments containing monocaprylin significantly reduced the population of E. sakazakii (P < 0.05) compared with the controls. Monocaprylin (50 mM) reduced the pathogen by >5 log CFU/ml by 1 h of incubation at 37 or 23 degrees C and by 24 h of incubation at 8 or 4 degrees C. Results indicate that monocaprylin could potentially be used to inactivate E. sakazakii in reconstituted infant formula; however, sensory studies are warranted before its use can be recommended.     

木犀草素与叶酸对黄曲霉毒素B1致食管上皮细胞毒性及MTHFR基因高甲基化的影响

目的：研究木犀草素（luteolin,LUT）与叶酸（folic acid,FA）对黄曲霉毒素B1（aflatoxin B1,AFB1）诱导损伤的人正常食管上皮细胞（human normal esophageal epithelial cells,HEEC）MTHFR基因甲基化的影响。方法：不同浓度（0、13、25、50、100、200 μmol/L）AFB1染毒HEEC 24、48、72 h,CCK-8法检测细胞活力;将HEEC分为空白对照组、AFB1染毒组（200 μmol/L）、LUT干预组（160 μmol/L）、FA干预组（20、200 μmol/L）以及联合干预组（160 μmol/L LUT＋20 μmol/L FA、160 μmol/L LUT＋200 μmol/L FA）,处理24 h后CCK-8法检测细胞活力,流式细胞术检测细胞周期及凋亡,Western blot检测MTHFR蛋白的表达水平,MassARRAY甲基化检测MTHFR基因启动子区甲基化的情况。结果：不同浓度的AFB1染毒HEEC 24、48、72 h均可以抑制细胞增殖,而经LUT和FA干预后,与AFB1染毒组相比,LUT及联合干预组细胞周期阻滞显著减少（P＜0.05）,细胞抑制率及凋亡率显著降低（P＜0.05）,MTHFR蛋白表达上调有所改善（P＜0.05）。且LUT与FA及二者联合对MTHFR基因启动子区高甲基化水平均有降低作用（P＜0.05）。结论：AFB1对HEEC有毒性作用,表现在增殖抑制、周期阻滞,促进凋亡,上调了MTHFR蛋白的表达,LUT干预可减弱这些损伤,对AFB1所致毒性起到一定的保护作用。AFB1提高了MTHFR基因启动子区甲基化水平,导致表观遗传的改变。LUT与FA及联合作用可以降低该甲基化水平,改善该表观遗传的改变。     

In vitro inactivation of Escherichia coli O157:H7 in bovine rumen fluid by caprylic acid

The antibacterial effect of caprylic acid (35 and 50 mM) on Escherichia coli O157:H7 and total anaerobic bacteria at 39 degrees C in rumen fluid (pH 5.6 and 6.8) from 12 beef cattle was investigated. The treatments containing caprylic acid at both pHs significantly reduced (P < 0.05) the population of E. coli O157:H7 compared with that in the control samples. At pH 5.6, both levels of caprylic acid killed E. coli O157:H7 rapidly, reducing the pathogen population to undetectable levels at 1 min of incubation (a more than 6.0-log CFU/ml reduction). In buffered rumen fluid at pH 6.8, 50 mM caprylic acid reduced the E. coli O157:H7 population to undetectable levels at 1 min of incubation, whereas 35 mM caprylic acid reduced the pathogen by approximately 3.0 and 5.0 log CFU/ml at 8 and 24 h of incubation, respectively. At both pHs, caprylic acid had a significantly lesser (P < 0.05) and minimal inhibitory effect on the population of total anaerobic bacteria in rumen compared with that on E. coli O157:H7. At 24 h of incubation, caprylic acid (35 and 50 mM) reduced the population of total anaerobic bacteria by approximately 2.0 log CFU/ml at pH 5.6, whereas at pH 6.8, caprylic acid (35 mM) did not have any significant (P > 0.05) inhibitory effect on total bacterial load. Results of this study revealed that caprylic acid was effective in inactivating E. coli O157:H7 in bovine rumen fluid, thereby justifying its potential as a preslaughter dietary supplement for reducing pathogen carriage in cattle.     

降黄曲霉毒素B1 菌株发酵条件的研究

对黄曲霉毒素B1(AFB1)降解菌株NMO-3 进行发酵培养基和培养条件优化,以期提高AFB1 降解率。方法：研究不同碳源、氮源、金属离子对AFB1 降解率的影响,最后选出最佳碳源、氮源和金属离子,通过正交回归试验,最后得出三者配方比。培养条件研究主要包括：初始pH 值、接种量、温度、种龄和降解时间等因素。结果：最终确定优化发酵培养基配方：果糖1.0%、胰蛋白胨1.0%、MgCl2 0.05mmol/L、其他发酵条件：起始pH 值为7.5、装液量25ml/300ml、接种量5%(V/V)、种子液培养时间为12h、控制降解温度为35℃、摇床转速140r/min、降解时间为72h。结论：经培养基成分和发酵参数的优化,AFB1 的降解率达到94.29%。     

植物乳杆菌F22 对黄曲霉毒素B1 的吸附特性

采用体外筛选法从14 株乳酸杆菌中筛选能吸附黄曲霉毒素B1(AFB1)的菌株,并探讨其吸附特性和机理。结果表明,植物乳杆菌F22 吸附率最高;F22 处理AFB1 30min 的吸附率较处理4h 高(P ＜ 0.01);热处理使吸附率极显著上升(P ＜ 0.01);而人工胃肠液处理则导致吸附率显著下降(P ＜ 0.05);冻干过程对F22 吸附率的影响不显著(P ＞ 0.05)。乳酸杆菌对AFB1 的吸附具有菌株特异性,吸附效果与细菌细胞壁的组成和结构相关。     

嗜盐四联球菌对黄曲霉毒素B1生物降解的研究

该实验主要研究了嗜盐四联球菌（Tetraphylococcus halophila）对黄曲霉毒素B1（AFB1）的降解。研究嗜盐四联球菌不同接种量及不同浓度AFB1对降解效果的影响,检测嗜盐四联球菌上清液不同处理条件及金属离子对AFB1降解效果的影响,并利用扫描电镜（SEM）观察了嗜盐四联球菌在AFB1毒素环境中的微观形态。结果表明,嗜盐四联球菌接种量为1%,发酵72 h时对AFB1的降解率可达到70.11%,降解活性物质主要存在于上清液中,且具有一定的耐热性。Ca2+抑制上清液对AFB1的降解,AFB1降解率降至40.32%;Zn2+促进上清液对AFB1的降解,AFB1降解率提高至75.52%,扫描电镜结果表明,与AFB1共培养72 h后,嗜盐四联球菌细胞壁褶皱转好。     

鼠李糖乳杆菌对黄曲霉毒素B1的降解及对 肝损伤的保护作用

目的分析鼠李糖乳杆菌(Lactobacillus rhamnosus GG,LGG)对黄曲霉毒素B_1(aflatoxin B_1,AFB_1)的降解能力,阐述LGG对由AFB_1引起的肝损伤的保护作用。方法利用LGG培养液、LGG上清液组、LGG菌体、热处理后上清液和热处理后LGG菌体处理AFB_1,利用高效液相色谱法测定AFB_1的残留量,分析LGG对AFB的降解能力。利用低、中和高剂量的LGG菌液灌胃由AFB_1引起肝损伤的大鼠,并以空白和阳性作为对照组,测定大鼠的血清肝功能及肝组织抗氧化指标,分析LGG对肝损伤的保护作用。结果 AFB_1降解实验表明LGG菌液对AFB_1具有显著的降解作用(P0.05),36 h能够降解(92.01±2.02)%的AFB_1。降解作用是由菌体和LGG的代谢产物共同作用的结果。大鼠血清肝功能及肝组织抗氧化指标结果表明低、中和高剂量的LGG灌胃给药均能显著改善因AFB_1引起的大鼠肝功能和肝组织抗氧化指标异常(P0.05)。结论 LGG对AFB_1具有良好的降解作用,且能够有效抑制因AFB_1引起的肝损伤。     

Production of free conjugated linoleic acid by Lactobacillus acidophilus and Lactobacillus casei of human intestinal origin

A gas chromatographic procedure was used for analysis of conjugated linoleic acid (CLA) isomers cis-9, trans-11-octadecadienoic; trans-10, cis-12 octadecadienoic; and trans-9, trans-11-octadecadienoic (c9t11, t10c12, t9t11) produced by lactobacilli. Four different cultures, two strains each of Lactobacillus acidophilus and Lactobacillus casei were tested for their ability to produce CLA from free linoleic acid in MRS broth supplemented with linoleic acid. Different concentrations of linoleic acid (0, 0.05, 0.1, 0.2 and 0.5 mg/ml) were added to MRS broth, inoculated with the lactobacilli, and incubated at 37 degrees C. Viable counts and amounts of individual isomers of CLA (c9t11, t10c12, t9t11) were measured at 0, 24, 48, and 72 h. All the cultures were able to produce free CLA in media supplemented with linoleic acid. Maximum production of CLA (80.14 to 131.63 microg/ml) was observed at 24 h of incubation in broth containing 0.02% of free linoleic acid. No significant (P > 0.05) increases in total CLA levels were observed after 24 h of incubation. The ability of the cultures to produce CLA in skim milk supplemented with 0.02% free linoleic acid also was studied. In this medium, the total amounts of free CLA after 24 h of incubation ranged from 54.31 to 116.53 microg/ml. The use of lactic acid bacteria able to form free CLA in cultured dairy products may have potential health or nutritional benefits. Free CLA in the products likely would be more readily available for absorption from the digestive tract than if it were incorporated into the cells of the starter culture.     

重组漆酶降解黄曲霉毒素B1分子对接分析及产物结构解析

以重组漆酶lac3基因同源性最高的3KW7作为模板进行同源模建,采用分子对接预测漆酶与黄曲霉毒素B1（aflatoxin B1,AFB1）的结合模式,结果显示漆酶与AFB1可以相互作用,氢键是其关键作用力,漆酶可用于黄曲霉毒素的降解。随后,通过实际的降解实验进行验证,响应面优化获得AFB1降解率最优的条件为底物AFB1 1 μg、孵育时间15 h、孵育温度34 ℃、酶活力2 U,降解率可达91.08%。在此条件下利用超高效液相色谱-飞行时间串联质谱分析AFB1降解产物结构,发现4 个主要降解产物,根据其二级质谱信息和精确分子质量,推测出降解产物的分子式分别为C16H22O4、C14H16N2O2、C7H12N6O和C24H30O6。     

Effect of surface roughness and stainless steel finish on Listeria monocytogenes attachment and biofilm formation

The purpose of this study was to evaluate the effect of surface roughness (Ra) and finish of mechanically polished stainless steel (Ra = 0.26 +/- 0.05, 0.49 +/- 0.10, and 0.69 +/- 0.05 microm) and electropolished stainless steel (Ra = 0.16 +/- 0.06, 0.40 +/- 0.003, and 0.67 +/- 0.02 microm) on Listeria adhesion and biofilm formation. A four-strain cocktail of Listeria monocytogenes was used. Each strain (0.1%) was added to 200 ml of tryptic soy broth (TSB), and coupons were inserted to the mixture for 5 min. For biofilm formation, coupons with adhesive cells were incubated in 1:20 diluted TSB at 32 degrees C for 48 h. The experiment was performed by a randomized block design. Our results show that the level of Listeria present after 48 h of incubation (mean = 7 log CFU/cm2) was significantly higher than after 5 min (mean = 6.0 log CFU/cm2) (P < 0.01). No differences in initial adhesion were seen in mechanically finished (mean = 6.7 log CFU/cm2) when compared with electropolished stainless steel (mean = 6.7 log CFU/cm2) (P > 0.05). Listeria initial adhesion (values ranged from 5.9 to 6.1 log CFU/cm2) or biofilm formation (values ranged from 6.9 to 7.2 log CFU/cm2) was not significantly correlated with Ra values (P > 0.05). Image analysis with an atomic force microscope showed that bacteria did not colonize the complete surface after 48 h but were individual cells or grouped in microcolonies that ranged from 5 to 10 microm in diameter and one to three cell layers in thickness. Exopolymeric substances were observed to be associated with the colonies. According to our results, electropolishing stainless steel does not pose a significant advantage for food sanitation over mechanically finished stainless steel.     

Excretion of aflatoxin M1 in milk of dairy ewes treated with different doses of aflatoxin B1

Two experiments were conducted to study the amount of aflatoxin M1 (AFM1) in milk in response to feeding aflatoxin B1 (AFB1). In experiment 1, four dairy ewes in early lactation received a single dose of pure AFB1 (2 mg). Individual milk samples were collected during the following 5 d to measure AFM1 concentration. The average excretion of AFM1 in milk followed an exponential decreasing pattern, with two intermediate peaks at 24 and 48 h. No AFM1 was detected in milk at 96 h after dosing. The mean rate of transfer of AFB1 into AFM1 in milk was 0.032%, with a high individual variability (SD = 0.017%). In experiment 2, 16 dairy ewes in midlactation were divided into four groups that received different daily doses of AFB1 (0, 32, 64, and 128 microgram for control and groups T1, T2, and T3, respectively) for 14 d. Pure AFB1 was administered to each animal divided in two daily doses. Individual milk samples were collected at 12, 24, 36, 48, 72, 96, 144, 216, and 312 h after the first AFB1 administration, during the intoxication period, and every 24 h for 7 d after the withdrawal of AFB1. AFM1 was detected in the milk of all animals of the treated groups at 12 h after the administration of AFB1. In all treated groups, milk AFM1 concentration increased from 12 to 144 h after the beginning of administration. It then decreased, reaching a stable concentration at 216 and 312 h after the first administration. No AFM1 was detected in milk 3 d after the last administration of AFB1. Milk AFM1 concentration measured at steady-state condition was significantly affected by the AFB1 dose (0.031, 0.095, and 0.166 in T1, T2, and T3 groups, respectively), with a linear relationship between AFB1 dose and milk AFM1 concentration (R2 = 77.2%). The carryover (AFM1/AFB1 ratio) was not significantly affected by treatment, and its mean value was 0.112% (SE = 0.011). The carryover was lower than that reported for dairy cattle and goats, suggesting a better ability of sheep to degrade AFB1.