外毒危害何其多

食品污染的健康危害1．致病性细菌和病毒可导致腹泻和食物中毒。如肉类中的寄生虫或寄生虫卵在加工过程未被杀灭，可导致寄生虫病。霉菌与霉菌毒素污染食品可致肝脏损害、霉菌毒素中毒、致畸、致突变、肝癌。如在霉变谷物、玉米、花生中广泛存在的黄曲霉毒素，有很强的毒性，     

黄曲霉素合成相关基因表达与环境因素的关系

简单介绍了黄曲霉毒素的发现、分布、危害和范围,详细叙述了黄曲霉毒素生物合成中相关基因的表达与调控,概述了黄曲霉毒素合成中的关键基因、酶和调控因子重要性,分析了影响黄曲霉毒素合成的环境因素。不仅在基础理论上对黄曲霉毒素合成机理进行了深入探讨,而且在应用研究上为减少粮食和食品受到重金属污染和黄曲霉毒素危害提供了新的思路。     

黄曲霉毒素生物合成的遗传调控研究进展

黄曲霉毒素是一类具有较强毒性和致癌力的次级代谢产物,在小麦、水稻、玉米和花生等多种粮食、油料、饲料和食品中检出率均比较高。因此,黄曲霉毒素不仅给人和动物的健康造成极其严重的威胁,而且也给食品和饲料等行业造成了巨大的经济损失。黄曲霉毒素主要由黄曲霉和寄生曲霉产生。自上个世纪60年代首次发现黄曲霉毒素以来,研究者在黄曲霉毒素合成途径、降解、合成机制和致病机理等方面做了大量研究。本文主要综述近年来国内外以黄曲霉为对象的黄曲霉毒素合成的遗传调控机制研究进展。从转录调控、蛋白翻译后修饰、信号转导途径、参与生长发育和形态建成的蛋白和其他酶等方面对黄曲霉毒素合成机制展开综述,为今后进一步深入系统研究黄曲霉毒素合成机制奠定基础,同时为制定防治黄曲霉及其毒素的策略提供理论基础。     

基于特异性生物识别分子的黄曲霉毒素快速分析方法研究进展

黄曲霉毒素是黄曲霉菌和寄生曲霉菌分泌的次级代谢产物,容易污染粮食作物及其制品,主要存在于发霉的粮食、豆类、坚果及与其相关食品中。黄曲霉毒素,具有极强的毒性和致癌性,尤其是黄曲霉毒素B1,是目前已发现的最强的天然致癌物质,严重威胁人类健康。目前食品中黄曲霉毒素的检测以高效液相色谱、液质联用等仪器分析方法为主,然而仪器分析方法具有设备昂贵、操作繁琐、需要专业人员等不足。近年来以特异性生物分子(抗体、重组抗体、适配体等)识别黄曲霉毒素,并结合不同的信号报告分子,建立了一系列黄曲霉毒素分析方法,检测快速、灵敏并易于操作,在食品安全领域广泛应用。着重从黄曲霉毒素的生物识别分子和信号报告分子两方面介绍目前黄曲霉毒素的快速检测手段,并对其进行比较和评价,同时对黄曲霉毒素快速检测方法的发展方向进行展望。     

利用拮抗物生物防治黄曲霉毒素

黄曲霉是引起粮食霉变的主要真菌之一,粮食和饲料在储藏过程中易受其污染[1]。黄曲霉最大的危害是其产生的次级代谢物黄曲霉毒素(Aflatoxins),黄曲霉毒素不仅能引起人类及各种动物的急慢性中毒,而且具有致癌、致畸、致突变作用。因此,如何有效地防止黄曲霉毒素污染花生等农产品已成为一个亟待解决的     

沈阳地区主要粮食霉菌污染情况调查

粮食是人类食品的主要原料,在收获、保藏和加工过程中遇到适宜温湿环境容易繁殖霉菌。其中有些霉菌产生霉素,特别是产生极毒的黄曲霉毒素。国内外大量调查资料证实:黄曲霉毒素是一种     

黄曲霉毒素生物防控菌的筛选及鉴定

筛选黄曲霉毒素生物防控菌,为黄曲霉毒素的生物防控提供支持。以花生原产地土壤为材料,采用牛津杯法筛选所需菌株。对筛选出的拮抗菌株进行抑制产毒曲霉菌株的生长、产孢、降解黄曲霉毒素实验。筛选出2株黄曲霉毒素生防细菌,编号21-1-2、17-3,经鉴定,拮抗菌21-1-2为枯草芽胞杆菌,拮抗菌17-3为地衣芽胞杆菌。分别对拮抗菌对曲霉孢子萌发的抑制、抑制黄曲霉的生长和菌丝延长以及减少黄曲霉毒素的产生、对黄曲霉毒素的分解作用等几个方面进行研究,结果表明,拮抗菌可以明显抑制产毒曲霉孢子的萌发、生长、菌丝的延长,减少黄曲霉毒素的产生以及分解黄曲霉毒素。     

黄曲霉毒素生物合成径调节基因aflR

黄曲霉毒素生物合成途径调节基因在黄曲霉毒素产生过程中发挥十分重要的作用,它为绝大多数黄曲霉毒素合成相关基因的表达所必需。黄曲霉毒素生物合成途径调节基因的启动子中,含有若干真菌转录因子同源物的假定结合位点。AflR蛋白是黄曲霉毒素生物合成途径中的主要正性转录因子,它调节大多数黄曲霉毒素合成相关基因,也包括其自身基因的表达。     

外毒危害何其多

<正>食品污染的健康危害1.致病性细菌和病毒可导致腹泻和食物中毒。如肉类中的寄生虫或寄生虫卵在加工过程未被杀灭,可导致寄生虫病。霉菌与霉菌毒素污染食品可致肝脏损害、霉菌毒素中毒、致畸、致突变、肝     

黄曲霉菌株(Q101)的筛选、鉴定及产毒条件的研究

据报道,黄曲霉毒素M_1(AFTM_1)的致癌性仅次于黄曲霉毒素B_1(AFTB_1)。AFTM_1是AFTB_1的代谢产物。目前对AFTB_1在动物体内的代谢过程和作用机制的研究很重视。AFTM_1标准品在流行病学调查及食品(特别是乳制品、肉类等)卫生检测工作中的需要量较     

Factors influencing the inhibition of aflatoxin production in corn by Aspergillus niger

Aspergillus niger, a mold commonly associated with Aspergillus flavus in damaged corn, interferes with the production of aflatoxin when grown with A. flavus on autoclaved corn. The pH of corn-meal disks was adjusted using NaOH-HCl, citric acid-sodium citrate, or a water extract of A. niger fermented corn. Aflatoxin formation was completely inhibited below pH 2.8-3.0, irrespective of the system used for pH adjustment. When grown in association with A. flavus NRRL 6432 on autoclaved corn kernels, A. niger NRRL 6411 lowered substrate pH sufficiently to suppress aflatoxin production. The biodegradation of aflatoxin B1 or its conversion to aflatoxin B2a were eliminated as potential mechanisms by which A. niger reduces aflatoxin contamination. A water extract of corn kernels fermented with A. niger caused an additional inhibition of aflatoxin formation apart from the effects of pH.     

Mold flora and aflatoxin contamination of stored and cooked samples of pearl millet in the Paharia tribal belt of Santhal paragana, Bihar, India

Stored and cooked samples of pearl millet (Pennesetum typhoides), which is regularly consumed as food by the Paharia tribe in the hilly regions of Santhal Pargana, Bihar State, India, that were harvested in January 1989 were analyzed for mold flora, natural occurrence of Aspergillus flavus and A. parasiticus, and incidence and levels of aflatoxin B1. Of the 22 fungal species isolated, A. flavus and A. parasiticus were the predominant species (63.8%) during the rainy season, followed by other species of Aspergillus, Penicillium, Fusarium, Rhizopus, Helminthosporium, and Curvularia. Screening of 169 A. flavus and A. parasiticus strains showed that 59 of them were toxigenic, producing various combinations of aflatoxins B1, B2, G1, and G2. The amounts of aflatoxin B1 ranged between 4 and 30 mg/100 ml of liquid medium. Analysis of stored and cooked samples also revealed a high incidence and alarming levels of naturally produced aflatoxin B1. Forty-nine of 75 stored and 16 of 38 cooked samples contained various combinations of aflatoxins. The levels of aflatoxin B1 ranged between 17 and 2,110 ppb in stored samples and 18 and 549 ppb in cooked samples. The correlation of insect damage with A. flavus and A. parasiticus incidence and quantity of aflatoxin B1 was found to be insignificant.     

Mold flora and aflatoxin contamination of stored and cooked samples of pearl millet in the Paharia tribal belt of Santhal paragana, Bihar, India.

Stored and cooked samples of pearl millet (Pennesetum typhoides), which is regularly consumed as food by the Paharia tribe in the hilly regions of Santhal Pargana, Bihar State, India, that were harvested in January 1989 were analyzed for mold flora, natural occurrence of Aspergillus flavus and A. parasiticus, and incidence and levels of aflatoxin B1. Of the 22 fungal species isolated, A. flavus and A. parasiticus were the predominant species (63.8%) during the rainy season, followed by other species of Aspergillus, Penicillium, Fusarium, Rhizopus, Helminthosporium, and Curvularia. Screening of 169 A. flavus and A. parasiticus strains showed that 59 of them were toxigenic, producing various combinations of aflatoxins B1, B2, G1, and G2. The amounts of aflatoxin B1 ranged between 4 and 30 mg/100 ml of liquid medium. Analysis of stored and cooked samples also revealed a high incidence and alarming levels of naturally produced aflatoxin B1. Forty-nine of 75 stored and 16 of 38 cooked samples contained various combinations of aflatoxins. The levels of aflatoxin B1 ranged between 17 and 2,110 ppb in stored samples and 18 and 549 ppb in cooked samples. The correlation of insect damage with A. flavus and A. parasiticus incidence and quantity of aflatoxin B1 was found to be insignificant.     

Substrate-induced lipase gene expression and aflatoxin production in Aspergillus parasiticus and Aspergillus flavus

AIMS: To establish a relationship between lipase gene expression and aflatoxin production by cloning the lipA gene and studying its expression pattern in several aflatoxigenic and nontoxigenic isolates of Aspergillus flavus and A. parasiticus. METHODS AND RESULTS: We have cloned a gene, lipA, that encodes a lipase involved in the breakdown of lipids from aflatoxin-producing A. flavus, A. parasiticus and two nonaflatoxigenic A. flavus isolates, wool-1 and wool-2. The lipA gene was transcribed under diverse media conditions, however, no mature mRNA was detected unless the growth medium was supplemented with 0.5% soya bean or peanut oil or the fungus was grown in lipid-rich medium such as coconut medium. The expression of the lipase gene (mature mRNA) under substrate-induced conditions correlated well with aflatoxin production in aflatoxigenic species A. flavus (SRRC 1007) and A. parasiticus (SRRC 143). CONCLUSIONS: Substrate-induced lipase gene expression might be indirectly related to aflatoxin formation by providing the basic building block 'acetate' for aflatoxin synthesis. No direct relationship between lipid metabolism and aflatoxin production can be ascertained, however, lipase gene expression correlates well with aflatoxin formation. SIGNIFICANCE AND IMPACT OF THE STUDY: Lipid substrate induces and promotes aflatoxin formation. It gives insight into genetic and biochemical aspects of aflatoxin formation.     

Molasses supplementation promotes conidiation but suppresses aflatoxin production by small sclerotial Aspergillus flavus

AIMS: To find a supplemental ingredient that can be added to routinely used growth media to increase conidial production and decrease aflatoxin biosynthesis in small sclerotial (S strain) isolates of Aspergillus flavus. METHODS AND RESULTS: Molasses was added to three commonly used culture media: coconut agar (CAM), potato dextrose agar (PDA), and vegetable juice agar (V8) and production of conidia, sclerotia, and aflatoxins by A. flavus isolate CA43 was determined. The effect of nitrogen sources in molasses medium (MM) on production of conidia, sclerotia and aflatoxins was examined. Water activity and medium pH were also measured. Conidia harvested from agar plates were counted using a haemocytometer. Sclerotia were weighed after drying at 45 degrees C for 5 days. Aflatoxins B(1) and B(2) were quantified by high-performance liquid chromatography. Addition of molasses to the media did not change water activity or the pH significantly. Supplementing CAM and PDA with molasses increased conidial production and decreased aflatoxins. Two-fold increased yield of conidia was found on MM, which, like V8, did not support aflatoxin production. Adding ammonium to MM significantly increased the production of sclerotia and aflatoxins, but slightly decreased conidial production. Adding urea to MM significantly increased the production of conidia, sclerotia and aflatoxins. CONCLUSIONS: Molasses stimulated conidial production and inhibited aflatoxin production. Its effect on sclerotial production was medium-dependent. Water activity and medium pH were not related to changes in conidial, sclerotial or aflatoxin production. Medium containing molasses alone or molasses plus V8 juice were ideal for conidial production by S strain A. flavus. SIGNIFICANCE AND IMPACT OF THE STUDY: Insight into molecular events associated with the utilization of molasses may help to elucidate the mechanism(s) that decreases aflatoxin biosynthesis. Targeting genetic parameters in S strain A. flavus isolates may reduce aflatoxin contamination of crops by reducing the survival and toxigenicity of these strains.     

Interactions of saprophytic yeasts with a nor mutant of Aspergillus flavus.

The nor mutant of Aspergillus flavus has a defective norsolorinic acid reductase, and thus the aflatoxin biosynthetic pathway is blocked, resulting in the accumulation of norsolorinic acid, a bright red-orange pigment. We developed a visual agar plate assay to monitor yeast strains for their ability to inhibit aflatoxin production by visually scoring the accumulation of this pigment of the nor mutant. We identified yeast strains that reduced the red-orange pigment accumulation in the nor mutant. These yeasts also reduced aflatoxin accumulation by a toxigenic strain of A. flavus. These yeasts may be useful for reducing aflatoxin contamination of food commodities.     

Detection of toxigenic isolates of Aspergillus flavus and related species on coconut cream agar

A new readily-prepared medium, coconut cream agar, was developed for the detection of aflatoxin production by isolates of Aspergillus flavus and related species. Coconut cream agar, which comprised coconut cream (50%) and agar (1.5%), detected isolates of A. flavus more effectively than the synthetic media tested and was as effective as media containing desiccated coconut. Fluorescence colouring of colonies grown on coconut cream agar could be used to differentiate A. flavus from A. parasiticus and A. nomius. In addition, conidial colour of A. flavus and A. nomius was quite distinct from that of A. parasiticus.     

Bright Greenish-Yellow Fluorescence and Aflatoxin in Agricultural Commodities

The corn milling industry has widely accepted the presence of bright greenish-yellow fluorescence under a black light as a presumptive indicator of aflatoxin (a poison produced by the mold Aspergillus flavus). This test was applied to wheat, oats, barley, rice, coconut, white corn, yellow corn, peanuts, sorghum, and soybeans, and evaluated in the laboratory. Our study supported the use of bright greenish-yellow fluorescence as a presumptive test for aflatoxin in wheat, oats, barley, corn, and sorghum.     

Fungal Contamination of Raw Materials of Some Herbal Drugs and Recommendation of <Emphasis Type="Italic">Cinnamomum camphora</Emphasis> Oil as Herbal Fungitoxicant

The paper explores fungal infection and aflatoxin B(1) contamination of six medicinal plant samples viz. Adhatoda vasica Nees, Asparagus racemosus Linn., Evolvulus alsinoides Linn., Glycyrrhiza glabra Linn., Plumbago zeylanica Linn. and Terminalia chebula Retz. A total of 858 fungal isolates were detected from the raw materials. Maximum number of fungal isolates was detected from A. racemosus (228). The genus Aspergillus was found to be the most dominant genus causing infection to most of the raw materials. Among the 32 isolates of A. flavus tested, 13 isolates were found to be toxigenic elaborating aflatoxin B(1). The highest elaboration of aflatoxin B(1) was 394.95 ppb by the isolates of A. flavus from G. glabra. The essential oil of Cinnamomum camphora (L.) Presl showed efficacy in arresting aflatoxin B(1) by the toxigenic strain. The growth of a toxigenic strain of A. flavus decreased progressively with increasing concentration of essential oil from leaves of C. camphora. The oil completely inhibited aflatoxin B(1) production even at 750 ppm. Hence, the oil of C. camphora is recommended as herbal fungitoxicant against the fungal contamination of the raw materials.     

Direct visual detection of aflatoxin synthesis by minicolonies of Aspergillus species.

Single-spore colonies of Aspergillus flavus and Aspergillus parasiticus, grown for 4 to 5 days at 25 degrees C on a coconut extract agar containing sodium desoxycholate as a growth inhibitor, produced aflatoxin, readily detectable as blue fluorescent zones under long-wave (365 nm) UV light. Over 100 colonies per standard petri dish were scored for aflatoxin production by this procedure. Progeny from some strains remained consistently stable for toxin production after repeated subculture, whereas instability for toxin synthesis was revealed among progeny from other strains. Spore color markers were used to rule out cross-contamination in monitoring strains. A yellow-spored and nontoxigenic strain of A. flavus, reported previously to produce aflatoxin in response to cycloheximide treatment, proved to be toxin negative even after repeated exposure to cycloheximide. Extended series of progeny from another strain of A. flavus and from a strain of A. parasiticus were each compared by this plating procedure and by fluorometric analysis for aflatoxin when grown in a coconut extract broth. Both of these strains showed variation for toxin synthesis among their respective progeny, and specific progeny showed a good correlation for aflatoxin synthesis when examined by the two procedures.