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.     

Biological degradation of aflatoxin B1 by Rhodococcus erythropolis cultures

Aflatoxin contamination of food and grain poses a serious economic and health problem worldwide, but particularly in Africa. Aflatoxin B(1) (AFB(1)) is extremely mutagenic, toxic and a potent carcinogen to both humans and livestock and chronic exposure to low levels of AFB(1) is a concern. In this study, the biodegradation of aflatoxin B(1) (AFB(1)) by Rhodococcus erythropolis was examined in liquid cultures using thin layer chromatography (TLC), high performance liquid chromatography (HPLC), electro spray mass spectrometry (ESMS) and liquid chromatography mass spectrometry (LCMS). AFB(1) was effectively degraded by extracellular extracts from R. erythropolis liquid cultures. Results indicated that the degradation is enzymatic and that the enzymes responsible for the degradation of AFB(1) are extracellular and constitutively produced. Furthermore, the biodegradation of AFB(1) when treated with R. erythropolis extracellular fraction coincided with a loss of mutagenicity, as evaluated by the Ames test for mutagenicity.     

中国被毛孢降解黄曲霉毒素B1的特性研究

目的 分析中国被毛孢（Hirsutella sinensis）8#菌株降解黄曲霉毒素B1 (AFB1)的能力。方法 考察该菌株培养液、菌丝体悬液和上清液去除AFB1的能力;利用洗脱和萃取法区分生物降解和可逆吸附AFB1;研究不同初始AFB1浓度、温度、pH和金属离子对其降解能力的影响;对AFB1降解液进行高效液相色谱和薄层色谱分析。结果 H.sinensis培养液和菌体降解效果显著（P<0.05）,96 h后对初始浓度100 ng/mL的AFB1降解率分别是96.90%±4.39% 和 97.93%±2.92%。磷酸盐缓冲液洗脱液和甲醇萃取液均未检测到AFB1,证实了该菌生物降解AFB1。菌株AFB1降解效果与初始浓度密切相关。当反应温度25 ℃,pH 7.0时,培养液作用72 h后降解率为99.90%±0.18%。同时,反应液中加入Fe2+有利于降解,而Mg2+却起到了抑制作用。高效液相色谱和薄层层析对产物分析表明,该菌株可将AFB1降解为至少为1种产物。结论 中国被毛孢8#菌株对AFB1有良好的降解作用,可用于生物降解真菌毒素的潜力菌株。     

黄曲霉毒素B1 降解产物及降解 安全性评价研究进展

为推动黄曲霉毒素B1(AFB1)降解技术的应用,寻求高效、快捷、安全的AFB1降解技术,促进食品中黄曲霉毒素的防治工作,对AFB1降解技术（物理降解技术、化学降解技术、生物降解技术）产生的降解产物以及降解后食品安全性评价研究的现状进行了论述,概括了降解技术的不足之处,并对降解技术的发展趋势进行展望。物理降解技术较适合大规模应用,但微波、脉冲电场、低温等离子体等技术仍处于研发阶段,无法确保该技术的安全性与可靠性。化学降解技术的研究比较常见,但存在食品感官品质变差,营养成分损失或破坏,易引入新的化学残留等不足。生物降解技术具有性质温和,不造成食品中营养成分大量损失且绿色环保等优点,但仍处于实验室研发阶段。在今后的研究中,应加强寻找新型纳米材料发展光降解技术、或各种技术联合使用、或利用基因工程联合酶法脱毒等新型技术,同时应更深入地研究降解机制、降解产物、降解路径以及降解产物的安全性。     

微波辅助碱法降解稻米粉中的黄曲霉毒素B1

针对稻米粉中可能存在的黄曲霉毒素污染问题,考察了微波辅助碱法处理对稻米粉中黄曲霉毒素B1(AFB1)的降解效果.研究结果表明:稻米粉中AFB1的初始浓度对其降解率的影响不显著;在碱处理pH10.0、料液比1∶25、单位质量微波功率7.5 W/g和处理时间9 min的条件下,稻米粉中AFB1的降解率为98.5％,AFB1残留量为1.32 μg/kg,符合国家标准(＜10 μg/kg);经该法制备的稻米粉,其基本成分变化不大,营养成分损失较少.由于微波辅助碱法降解条件温和、操作简单、降解效率高,可应用于受黄曲霉毒素污染的粮食物料.     

Reactive molecular dynamics simulation on degradation of aflatoxin B1 by cold atmospheric plasmas

Aflatoxins pose a threat to humans and animals and are not easily degraded. Cold atmospheric plasma (CAP) can effectively decontaminate aflatoxins in foods. In this study, a Reactive Molecular Dynamics (RMD) simulation was carried out to examine the interactions of reactive oxygen species (ROS) produced in CAP and aflatoxin B₁ (AFB₁). The simulation results indicated that ROS (O atoms, OH radicals, and H₂O₂ molecules considered in present study) can reduce the toxicity of AFB₁ by the addition reaction of the double C₈C₉ bond, the ring-opening reaction of the terminal furan ring, and the destruction of the lactone ring. The ketone carbonyl reduction and double CC bonds formation of cyclopentenone can also be observed in the simulation. The reaction pathways and the final products unveiled by simulation results agree well with the experimental observations, which clearly indicate that CAP can degrade AFB₁ by destroying the key structures of AFB₁ in a non-thermal way, and further suggest the optimized way to degrade aflatoxins in applications.Industrial relevanceReactive Molecular Dynamics simulations were applied to visualize the chemical damaging mechanism of AFB₁ upon the impact of reactive oxygen species during food processing by cold atmospheric plasma (CAP). Such detailed information about the pathways of specific ROS is difficult to obtain experimentally. These results can be used to understand the structural changes at the atomic level that could provide theoretical instruction to industrialists. This work can also contribute to the optimization of process parameters to drive the improvement of operating conditions and the development of CAP sources in the food industry.     

Aflatoxin B1 degradation by flavobacterium aurantiacum in the presence of reducing conditions and seryl and sulfhydryl group inhibitors

This study was undertaken to determine the effects of reducing conditions (L-cysteine) and seryl (phenylmethylsulfonyl fluoride) and sulfhydryl (divalent cadmium) group inhibitors on aflatoxin B1 (AFB1) degradation by Flavobacterium aurantiacum. High-performance liquid chromatography was used to determine AFB1 concentrations in 72-h cultures of F. aurantiacum. The addition of 0.1, 1, or 10 mM L-cysteine did not have any significant effect on AFB1 degradation by these cultures after incubation for 4, 24, or 48 h (P > 0.05). The addition of 0.1 mM phenylmethylsulfonyl fluoride did not significantly decrease AFB1 degradation (P > 0.05), but 1 mM phenylmethylsulfonyl fluoride significantly decreased AFB1 degradation after 4, 24, and 48 h of incubation (P < or = 0.05). No significant difference in AFB1 degradation was obtained with 0.1 mM Cd2+ after 4, 24, or 48 h of incubation (P > 0.05). The addition of 1 and 10 mM Cd2+ significantly decreased AFB1 degradation compared with the cells containing AFB1 alone after 4 and 24 h (P < or = 0.05). The addition of chelators, 1 mM EDTA and 1 mM o-phenanthroline, did not result in removal of inhibition of AFB1 degradation observed with 1 and 10 mM Cd2+. Higher concentration of chelators (>1 mM) are necessary to overcome the inhibitory effect. Further work on the cellular fractions and/or crude enzyme preparations is necessary to determine if indeed sulfhydryl and seryl groups of the enzymes are involved in AFB1 degradation (by maintaining either the structure or function of the enzyme).     

等离子体降解花生中黄曲霉毒素的影响因素

采用低温射频等离子体技术处理黄曲霉毒素B1(AFB1),通过HPLC分析其中AFB1的降解率,探究不同处理时间、处理功率等离子体和不同水分含量、颗粒大小、种类的花生对AFB1降解的影响。结果表明,在相同时间下等离子体处理功率越大,花生中的AFB1降解得越多,400 W时降解率为73.45%;在相同处理功率下,处理时间越长,花生中的AFB1降解越多,8 min后降解率为79.26%;在相同条件下,花生中水分含量越高,AFB1的降解率越高,含水量达到40%时降解率达到50%;花生的颗粒越小,AFB1的降解率越高,花生粉的降解率达到近60%;含油量越高的花生,其AFB1降解率越低,花生的含油量为45%时降解率只有45%。得出等离子体技术降解AFB1时,外界条件对降解有较大影响,该结果对实际应用有指导作用。     

嗜麦芽窄食单胞菌42-2降解黄曲霉毒素B1的效果研究

黄曲霉毒素B1（AFB1）对人类和家畜的健康危害很大。本文以嗜麦芽窄食单胞菌（Stenotrophomonas sp.42-2）为研究菌株,对其进行了急性毒理实验,并利用该菌的上清液、发酵液和胞外蛋白粗提取液分别进行了发霉玉米、饲料、生大黄、柏子仁和怀山药的黄曲霉毒素B1降解实验。结果表明:活菌制剂在2.56×1010 CFU个/m L剂量以下不会引起急性毒性反应。在菌株42-2的上清液、发酵液和胞外蛋白粗提取液的毒素降解实验中,三者对发霉玉米中AFB1的降解率分别为:74.90%、82.60%和65.40%;对饲料中AFB1的降解率分别为:77.60%、82.50%和71.20%;对生大黄中AFB1的降解率分别为:73%、78.10%和68.40%;对柏子仁中AFB1的降解率为:76%、79.50%和70.50%;对怀山药中AFB1的降解率分别为:65.30%、69.10%和61.10%。      

细菌M19降解黄曲霉毒素B1降解产物的毒性分析

黄曲霉毒素B_1(AFB_1)具有极强的毒性,致癌性和致突变性,对人类健康造成严重威胁。本研究基于实验室筛选保藏的AFB_1降解菌M19产生的AFB_1降解酶(PADE),采用致突变性实验(Ames实验)和HepG2细胞的细胞毒性实验对AFB_1降解后的毒性进行分析。研究发现, AFB_1经PADE降解后对鼠伤寒沙门氏菌TA98、TA100的回复突变数明显大于AFB_1对这些菌株的回变菌落数,与自发突变无明显差异,降解3 d后,其降解产物已表现出致突变阴性结果;与未处理细胞组相比,AFB_1降解产物作用于细胞的存活率均达到83%以上。结果表明,AFB_1经PADE降解后,其致突变性和细胞毒性均明显降低。     

花生组分对常压等离子体降解黄曲霉毒素B1的影响

采用常压等离子体技术处理黄曲霉毒素B_1(AFB_1),探究花生中的水分、蛋白质、脂肪酸、白藜芦醇、V_E等组分对常压等离子体降解AFB_1的影响。结果表明:纯乙腈体系中的AFB_1在170 V等离子处理100 s时的降解率为62.5%,分别加入6%的水分、25%的花生蛋白、4 mg/100 g的白藜芦醇、40 mg/100 g的V E、脂肪酸(含油酸、亚油酸和棕榈酸)以及多组分混合物后,AFB_1的降解率分别为72.25%、51.6%、60.12%、52.63%、58.3%和51.08%。与纯乙腈体系相比,添加水分后,AFB_1的降解率升高9.75%,而添加其它组分后,AFB_1的降解率都有所降低。因此,利用常压等离子技术降解AFB_1时,花生组分对降解率有不同程度的影响,这对实际应用有一定的参考价值。     

细菌降解黄曲霉毒素B1的研究进展

黄曲霉毒素B1是目前已发现的黄曲霉毒素中毒性最强的一种,其具有强肝毒性、高致突变性和高致畸性。广泛存在于农产品及饲料食品中,对人类健康存在严重威胁,同时对粮食和畜牧业造成严重的经济损失。细菌降解黄曲霉毒素B1是一种有效、安全和环保的解毒方法,该文通过对黄曲霉毒素B1降解的影响因素、细菌胞外酶和胞内酶等对黄曲霉毒素B1的降解机理以及黄曲霉毒素B1降解菌活性产物的应用研究等方面对细菌降解黄曲霉毒素B1进行了论述,并对细菌降解黄曲霉毒素B1应用前景进行展望,为以后更进一步研究提供较为全面的资料。     

Removal of cadmium from wastewaters by aragonite shells and the influence of other divalent cations

The effect of dissolved Zn, Co, Pb, Mg, and Ca on the uptake of cadmium by biogenic aragonite was investigated. Experiments were performed in batch-reactors using metal-cadmium-bearing solutions and shell fragments with diameters in different ranges, the solid/liquid ratio being 10 grams per liter. Different initial concentrations of cadmium and metals (1.0-0.005 mM) were used. Uptake takes place via heterogeneous nucleation of metal-bearing crystallites onto the shell surfaces. Cadmium removal occurs by surface precipitation of otavite. Under the conditions used here, Co and Ca as well as Pb < or = 0.3 mM and Zn < or = 0.3 mM do not have a significant effect on the removal of cadmium. At higher concentrations, Pb and Zn outcompete Cd for the dissolving carbonate ions and thus decrease significantly the Cd removal rates. In contrast, Mg has a slight enhancing effect. Pb and Zn are removed faster than Cd, precipitating as PbCO3, Pb3(CO3)2(OH)2, and Zn5(CO3)2(OH)6. Within 24-72 h, the concentrations of lead, cadmium, and zinc decrease until approximately 0.5 microM, and the presence of aragonite buffers the solution to a pH above 8 avoiding redissolution. The study demonstrates the high effectiveness of biogenic aragonite in removing Cd and other metals from polluted waters.     

碱法制备米蛋白过程中微波辅助降解黄曲霉毒素B1的研究

针对稻米中所存在的黄曲霉毒素污染的问题,本文研究了碱法制备米蛋白过程中微波辅助处理对黄曲霉毒素B1(AFB1)降解率的影响。结果表明,碱法制备米蛋白工艺可使AFB1浓度下降46.83%,米蛋白中AFB1残留浓度为33.91μg/kg,不符合国家标准(≤10μg/kg);基于该工艺研究,单位体积微波功率750W/L和微波处理时间7min为微波辅助碱法降解AFB1的最佳处理条件,AFB1降解率为88.51%,米蛋白中AFB1残留浓度为7.33μg/kg,符合国家标准。同时,AFB1初始浓度对微波辅助碱法降解AFB1的影响不显著,通过对微波辅助碱法降解AFB1工艺进行动力学模型拟合,表明该降解特征符合一级动力学模型。      

Binding of aflatoxin B1 by probiotic bacteria

The ability of six probiotic bacteria to bind a common food carcinogen, aflatoxin B₁, was assessed. The studied strains included Lactobacillus strains and one Bifidobacterium strain. The strains were incubated in vitro with alfatoxin B₁ and the toxin residue in the supernatant was measured using high‐performance liquid chromatography. The aflatoxin‐binding capacity of the strains was found to range from 5.8 to 31.3%. The results further support the observation that a number of probiotic bacteria are able to bind specific dietary contaminants. Although the extent of binding varies depending on the bacterial strain used, the data may explain some of the antimutagenic and anticarcinogenic effects of probiotic micro‐organisms. © 2000 Society of Chemical Industry     

In vivo toxicity assessment of aflatoxin B1-contaminated corn after ozone degradation

Corn is an important food and feedstuff in China and worldwide. The problems caused by aflatoxin B₁-contaminated corn (ACC) are of great concern. Our previous studies have demonstrated that ozone can effectively degrade AFB₁ in corn, prompting us to investigate the in vivo toxicity of treated ACC. In this study, 35 Kunming mice were used to assess the in vivo toxicity of ozone treated ACC. Results indicated that compared to mice fed with basal feedstuff (provided by the Shanghai SLAC Laboratory), those fed with ACC have significantly decreased mean weight as well as total protein (TP), albumin (ALB), and globulin (GLB) contents (p < 0.05). On the other hand, the liver and kidney/body weight ratio as well as the serum alanine transaminase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) levels significantly increased (p < 0.05). Obvious histopathological changes were found in the liver and kidney. When mice were fed with the ozone-treated ACC, no significant differences were observed in the mean weight, the liver and kidney/body weight ratio and in the major serum indexes ALT, TP, ALB, and GLB (p > 0.05). However, AST and ALP significantly increased (p < 0.05), and slight histopathological changes were found in liver tissues. This study indicated that ACC may lead to significant changes in various physiological characteristics and biochemical indexes in liver and kidney tissues, but ozone treatment of ACC could significantly reduce these changes.     

Removal of Aflatoxin B1 from Peanut Milk Inoculated with Flavobacterium aurantiacum

The ability of F. aurantiacum to reduce the aflatoxin B₁ (AFB₁) concentration was determined by inoculating about 10⁹ stationary phase cells in AFB₁-contaminated phosphate buffer (PB). non-defatted peanut milk (NDPM) and partially defatted peanut milk (PDPM). The AFB₁ concentration and cell populations were determined periodically throughout the incubation (30°C). After 24 hr, the concentration of AFB₁ decreased about 40% in PB, 23% in NDPM and 74% in PDPM. Viable cell population decreased less than one log₁₀ CFU/mL in all liquids but increased about 0.8 log₁₀ unit in control PDPM. AFB₁ recovery increased about 30% in proteolysed PDPM but proteolysis had no effect on recovery from NDPM.     

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。