丁酸梭菌发酵培养基的优化及发酵产物对黄曲霉毒素B1的降解

【背景】丁酸梭菌是专性厌氧的新一代芽孢益生菌,耐热、耐酸、抗逆性强,极具应用价值和开发前景。【目的】优化丁酸梭菌发酵培养基并初步研究其发酵液对黄曲霉菌的抑制作用和降解黄曲霉毒素B₁ (aflatoxin B₁, AFB₁)的能力。【方法】利用响应面法对发酵培养基进行优化,采用牛津杯法对丁酸梭菌发酵液抑制黄曲霉菌生长进行研究,并通过酶联免疫法测定发酵液对AFB₁的降解能力。【结果】优化后的发酵培养基为：葡萄糖18.1g/L,大豆蛋白胨29.7g/L,磷酸氢二钾3.8 g/L,氯化钠2.0 g/L,乙酸钠4.0 g/L,结晶硫酸镁1.2 g/L,L-半胱氨酸盐酸盐0.3 g/L。优化后的丁酸梭菌生物量由8.99×10⁸个/mL提高至2.28×10⁹个/mL,是优化前的2.54倍。丁酸梭菌发酵液对致病真菌黄曲霉菌的抑菌效果十分显著,其上清液经浓缩后对AFB₁降解72h的降解率达到68.65%,初步分析表明上清液中对AFB₁     

Substrate depletion during formation of aflatoxin and kojic acid on corn inoculated with Aspergillus flavus

During a period of 8 years 300 cases of dermatophytoses involving both hairy areas and the glabrous skin were found to be caused by M. canis. There was scalp involvement in 60%, including 8 infants and 27 adults; most of the adults presented Kerion-like lesions and presented various clinical aspects such as seborrhea capitis, folliculitis and discois lupus erythematosus. In the 21 patients showing invasion of the beard the clinical manifestations included superficial erythematosquamous patches with hyperemic slightly elevated margins, folliculitis or abscess-like lesions and Kerion-like lesions. Among the lesions found on the glabrous skin there were unusual aspects of tinea faciei in 19 adults, mimicking lymphocytic infiltration, granuloma faciale or discoid lupus erythematosus. Some of the cases of tinea corporis found in 70 patients also had lesions simulating various other dermatological entities, including erythema multiforme, psoriasiform eruption, pityriasis rosea and seborrheic dermatitis. The hands were invaded in 5 adults patients, with involvement of the finger nails in one. Repeated mycologic examinations were necessary to establish the true etiology in many of these cases.     

A signal-amplified electrochemical immunosensor for aflatoxin B1 determination in rice

A sensitive and simple electrochemical immunosensor based on enzymatic silver deposition amplification was constructed for the detection of aflatoxin B₁ (AFB₁) in rice. The immunosensor was based on an indirect competitive format between free AFB₁ and aflatoxin B₁-bovine serum albumin (AFB₁-BSA) conjugate immobilized on the electrode surface for binding to a fixed amount of anti-AFB₁ antibody. Then the alkaline phosphatase (ALP)-labeled anti-mouse immunoglobulin G (IgG) secondary antibody was bound to the electrode surface through reaction with primary antibody. Finally, ALP catalyzed the substrate, ascorbic acid 2-phosphate, into ascorbic acid that reduced silver ions in solution to metal silver deposited onto the electrode surface. Linear sweep voltammetry was carried out to quantify the metal silver, which indirectly reflected the amount of the analyte. The experimental parameters, such as the dilution ratio of antibody and the concentration of AFB₁-BSA conjugate, have been evaluated and optimized. At the optimal conditions, the working range of the electrochemical immunosensor was from 0.1 to 10 ng/ml with a detection limit of 0.06 ng/ml. Good recoveries were obtained for the detection of spiked rice samples. So, the proposed method in this article could find a good use for screening AFB₁ in real samples.     

A comparative evaluation of aflatoxin B1 genotoxicity in fish models using the Comet assay

Aflatoxin B₁ (AFB₁) is classified as a Group I hepatocarcinogen in humans by the International Agency for Research on Cancer (IARC). The alkaline Comet assay is a simple and rapid method by which DNA damage can be demonstrated as a function of tail moment. The present work is the first to evaluate the genotoxicity of AFB₁ in fish using the Comet assay. Two different species of fish were selected as models due to previously established sensitivity to AFB₁: rainbow trout (sensitive) and channel catfish (resistant). Fish were i.p. injected with 0.5 mg AFB₁/1 ml DMSO/1 kg body weight. The Comet assay was performed after 4 and 24 h on whole blood, liver, and kidney cells of both species. Trout blood and kidney tissue tested displayed significant (p<0.05) and extensive DNA damage (shown by increased tail moment) after 4 h which then decreased by 24 h. In liver cells, damage progressively increased over time. Conversely, similarly treated catfish showed no elevation in DNA damage over controls at the same doses. These results suggest that the Comet assay is a useful tool for monitoring the genotoxicity of mycotoxins such as AFB₁ and for evaluating organ specific effects of these agents in different species.     

Mortality and reproductive effects of avermectin B1 fed to German cockroaches

Newly emerged adult female German cockroaches, Blattella germanica (L.) (Dictyoptera: Blattellidae) fed avermectin B₁ at concentrations of 6.5 ppm and higher in the food exhibited high mortality at 10 days. Survivors of these dosages failed to reproduce. Lower dosages produced some mortality and inhibited mating and reproduction. Those individuals that did reproduce had normal-sized oothecae and the percent hatch was normal. The higher concentrations produced a marked inhibition of feeding which appeared to be related to toxicity rather than to unpalatability or repellency. When nymphs were fed avermectin B₁ for short periods, higher dosages were required to produce mortality. Young nymphs were the most susceptible. Feeding inhibition also occurred in these short-term studies, but the survivors reproduced normally as did the progeny from the females fed avermectin continuously. The possible use of avermectin B₁ in baits for cockroach control is discussed.

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Résumé Alimentées peu après la mue imaginale avec une nourriture contenant 6,5 ppm ou plus d'avermectine B₁, des femelles de B. germanica L. ont présenté une forte mortalité à 10 jours; les survivantes ne se sont pas reproduites. Des doses plus faibles ont provoqué quelque mortalité et quelque inhibition des accouplements et de la reproduction; les individus qui se sont reproduits avaient des oothèques de taille normale et le taux d'éclosion était correct. Les concentrations plus élevées ont provoqué une nette inhibition de l'alimentation, qui semblait être plus due à la toxicité qu'à la répulsion ou au goût. Quand des larves âgées ont été alimentées avec de l'avermectine B₁ pendant de brèves périodes, des doses plus élevées étaient nécessaires pour provoquer la mortalité. Les jeunes larves étaient les plus sensibles. Une inhibition de l'alimentation apparût dans ces études à court terme, mais les survivants se reproduisirent normalement, comme le firent les descendants des femelles alimentées continuellement avec de l'avermectine. La discussion porte sur l'utilisation éventuelle de l'avermectine B₁ dans des appâts pour lutter contre les blattes.

     

Naturally occurring chlorophyll derivatives inhibit aflatoxin B1-DNA adduct formation in hepatoma cells

The inhibitory effects of four chlorophyll derivatives (chlorophyllide [Chlide] a and b and pheophorbide [Pho] a and b) on aflatoxin B₁ (AFB₁)-DNA adduct formation, and on the modulation of hepatic glutathione S-transferase (GST) were evaluated in murine hepatoma (Hepa-1) cells. Enzyme-linked immunosorbent assay showed that pretreatment with Chlide or Pho significantly reduced the formation of AFB₁-DNA adducts, and that Pho was the most potent inhibitor. However, wash-out prior to adding AFB₁ totally eliminated inhibition by Childe and partially eliminated inhibition by Pho, indicating that the inhibitory effect of Chlide, and to some extent Pho, was mediated through direct trapping of AFB₁. Furthermore, spectrophotometric analysis showed that Pho treatment could increase GST activity in Hepa-1 cells. These observations indicate that the chlorophyll derivatives studied may attenuate AFB₁-induced DNA damage in the Hepa-1 cell by direct trapping of AFB₁. Pho provided additional protection not only by direct trapping, but also by increasing GST activity against hepatic AFB₁ metabolites.     

Processing of glutathionylcobalamin by a bovine B12 trafficking chaperone bCblC involved in intracellular B12 metabolism

Glutathionylcobalamin (GSCbl) is a biologically relevant vitamin B₁₂ derivative and contains glutathione as the upper axial ligand thought formation of a cobalt-sulfur bond. GSCbl has been shown to be an effective precursor of enzyme cofactors, however processing of the cobalamin in intracellular B₁₂ metabolism has not been fully elucidated. In this study, we discovered that bCblC, a bovine B₁₂ trafficking chaperone, catalyzes elimination of the glutathione ligand from GSCbl by using the reduced form of glutathione (GSH). Deglutathionylation products are base-off cob(II)alamin and glutathione disulfide, which are generated stoichiometrically to GSH. Although cob(I)alamin was not detected due to its instability, deglutathionylation is likely analogous to dealkylation of alkylcobalamins, which uses the thiolate of GSH for nucleophilic displacement. The catalytic turnover number for the deglutathionylation of GSCbl is ?1.62 ± 0.13 min⁻¹, which is, at least, an order of magnitude higher than that for elimination of upper axial ligands from other cobalamins. Considering the prevalence of GSH at millimolar concentrations in cells, our results explain the previous finding that GSCbl is more effective than other cobalamins for synthesis of enzyme cofactors.     

拟南芥抗凋亡突变体fbr136的分离鉴定与分析

植物细胞程序性死亡(programmed cell death,PCD)在植物的生长发育进程以及防御生物与非生物胁迫的过程中具有重要的作用.Fumonisin B1(FB1)是一种真菌毒素,是鞘脂生物合成途径中关键酶神经酰胺合酶(ceramide synthase)的竞争性抑制剂.FB1在动植物细胞中均能够诱导PCD.为了探索植物PCD的机制,通过筛选拟南芥抗FB1的突变体,分离鉴定了11个,fumonisin B1 resistant (fbr)突变体.遗传分析表明,这些突变体分别是由9个相同或者不同的遗传座位突变造成的.对其中一个代表性的突变体fbr136进行了详细的表型分析和初步遗传定位.fbr136对其他PCD诱导剂,例如H2O2或paraquat也表现出一定的抗性或耐受性,而且在fbr136突变体中FB1不能正常诱导PR1基因的表达,说明fbr136突变体PCD的发生可能受到阻碍.硝基四唑(Nitroblue tetrazolium,NBY)染色表明,FBl处理fbr136突变体后产生和积累活性氧(reactive oxygenspecies)比野生型植物显著降低,暗示其抗凋亡表型可能与活性氧的产生有关.推测FBR136可能是FB1在诱导PCD过程中,从鞘脂含量变化到活性氧积累变化这一途径的一个重要的调控因子.fbr136被定位于染色体Ⅲ上,与以往鉴定的抗FB1突变基因的定位都不同,因此,FBR136可能是FB1诱导PCD信号途径中的一个新基因.     

Is the expression of kinin B1 receptor related to intrahepatic vascular response?

Bradykinin elicits an intrahepatic vascular response (IHVR) mediated by the constitutive B₂ receptor (B₂R). The biological effects of kinins may also be mediated by the inducible B₁ receptor (B₁R). Aim: To verify if the hepatic B₁R expression modulates IHVR to kinins. Method: We evaluated the ability of bradykinin and B₁R agonists to elicit an IHVR in normal rats and in those submitted to acute or chronic inflammatory stimuli, fibrosis, cirrhosis, or hepatic regeneration. Results: Bradykinin-induced IHVR was similar in all groups. B₁R agonists did not elicit in any of them either a hypertensive or a hypotensive response. B₁ receptor induction was observed in all experimental groups (Western blot), except for the acute inflammatory group. Conclusion: B₁R hepatic expression did not modulate IHVR to kinins.     

Glutathione increases the binding affinity of a bovine B12 trafficking chaperone bCblC for vitamin B12

Intracellular B₁₂ metabolism involves a B₁₂ trafficking chaperone CblC that is well conserved in mammals including human. The protein CblC is known to bind cyanocobalamin (CNCbl, vitamin B₁₂) inducing the base-off transition and convert it into an intermediate that can be used in enzyme cofactor synthesis. The binding affinity of human CblC for CNCbl was determined to be K_d = ≈6–16 μM, which is relatively low considering sub-micromolar B₁₂ concentrations (0.03–0.7 μM) in normal cells. In the current study, we discovered that the base-off transition of CNCbl upon binding to bCblC, a bovine homolog of human CblC, is facilitated in the presence of reduced form of glutathione (GSH). In addition, GSH dramatically increases the binding affinity for CNCbl lowering the K_d from 27.1 ± 0.2–0.24 ± 0.09 μM. The effect of GSH is due to conformational change of bCblC upon binding with GSH, which was indicated by limited proteolysis and urea-induced equilibrium denaturation of the protein. The results of this study suggest that GSH positively modulates bCblC by increasing the binding affinity for CNCbl, which would enhance functional efficiency of the protein.     

Effect of dietary β-1,3 glucan on immune responses and disease resistance of healthy and aflatoxin B1-induced immunocompromised rohu (Labeo rohita Hamilton)

The immunostimulant β-1,3 glucan was fed at 0·1% in feed for 7 days to healthy and aflatoxin B₁(AFB₁)-induced immunocompromised fish, Labeo rohita (one of the major tropical carp species), in a 60 day trial. The effects of AFB₁, glucan and their interactions on non-specific and specific immunity levels and disease resistance of fish were studied. A single intraperitoneal injection of AFB₁at 1·25 mg kg⁻¹body weight) caused a significant (P< 0·05) reduction in non-specific immunity as measured through neutrophil phagocytic indices, serum bactericidal activity, and specific immunity as measured through bacterial agglutination titre against Edwardsiella tarda, as well as reduced protection against Aeromonas hydrophila challenge in comparison to control fish which were exposed neither to aflatoxin nor to glucan. Feeding of glucan to healthy fish raised the non-specific and specific immunity level and protection against bacterial infection compared with the control. Feeding of glucan to AFB₁-induced immunocompromised fish for 7 days significantly raised the degree of resistance against A. hydrophila challenge and the non-specific immunity level in comparison to non-treated AFB₁exposed fish. Although feeding of glucan was able to increase specific immunity, al measured through haemagglutination titre against sheep red blood cells, and bacterial (E. tarda) agglutination titre in healthy fish in comparison to all other groups, no significant increase in specific immunity to the aflatoxin-exposed group was seen.     

植物维生素B_6从头合成与代谢转换研究进展

维生素B6是一组可相互转换的吡啶衍生物的总称,包括吡哆醇、吡哆胺、吡哆醛、磷酸吡哆醇、磷酸吡哆胺和磷酸吡哆醛。其中,磷酸吡哆醛是140多种细胞酶的辅酶。至今发现两种VB6从头合成途径,DXP(1-脱氧-D-木酮糖-5-磷酸)依赖途径和DXP非依赖途径,前者仅存在于大肠杆菌和少量其他细菌,后者存在于其他所有VB6自养生物。除了VB6的从头合成,所有细胞生物体内还存在一条相似的补救途径,补救途径实现VB6各型的代谢转换。该文对近年来国内外有关植物VB6从头合成和代谢转换研究进展进行综述。     

Metabolism of aflatoxin B1 by Petroselinum crispum (parsley)

On administration of aflatoxin B₁ to whole parsley (Petroselinum crispum) plants, a derivative was formed, which was shown to be aflatoxicol by its chromatographic properties and mass spectrometry. Optimum conditions for the production of the derivative was on the second day after administration of the toxin to the plants, which were 90 days old after germination. Cell-free preparations of parsley were found not to produce aflatoxicol A from added aflatoxin B₁; instead they formed two new derivatives, which from chromatographic properties, were shown to be more polar than either aflatoxin B₁ or aflatoxicol A.     

Cytotoxicity of aflatoxin B1 and its chemically synthesised epoxide derivative on the A549 human epithelioid lung cell line

Aflatoxin B₁ (AFB₁) is a carcinogenic mycotoxin found in feeds and in airborne grain dusts. Aflatoxin B₁ requires biotransformation to the AFB₁-8,9 epoxide (AFBO) by a bioactivation system and subsequent covalent binding to DNA or proteins, to exert its carcinogenic potential. The lung contains cytochrome P₄₅₀, prostaglandin-H-synthase, lipoxygenase, epoxide hydrolase and other bioactivation enzymes, and is thus a potential target for the effects of AFB₁ via the routes of inhalation and ingestion. The A549 human epithelioid lung cell line and the methylthiazol tetrazolium (MTT) bioassay were used to investigate the cytotoxicity of AFB₁ and its chemically synthesised epoxide (AFBO) in vitro. Statistical analysis of the MTT results indicated that there were overall significant differences between the control and both the AFB₁-treated (p < 0.0001) and AFBO-treated cells (p = 0.00 2). However, there was no significant difference between AFB₁ and AFBO-treated cells, when the entire range of concentrations were assessed against each other (p = 0.2877). Whenanalysed at each concentration, only at 0.01 mM was there a significant difference between the effects of AFB₁ and AFBO (p = 0.0358). The results of this investigation show that AFB₁ and AFBO are both cytotoxic in the A549 cell line.This revised version was published online in October 2005 with corrections to the Cover Date.     

Towards the synthesis of light-stable coenzyme B12 analogs

The organometallic complex coenzyme B₁₂ (adenosyl cobalamin, AdoCbl) is not only an essential coenzyme in many biochemical reactions of most if not all living organisms but has lately been shown to play a crucial role in the regulation of B₁₂ related genes. As a consequence, coenzyme B₁₂ has been a target of intense research. However, the investigations of AdoCbl have often been hampered due to its high light-sensitivity leading to decomposition of the compound within a few seconds. Here, we describe a strategy to synthesize more light-stable coenzyme B₁₂ analogs, which show similar steric properties as adenosyl cobalamin. The synthesis, structural characterization as well as the pH dependent “base-on/base-off” behavior of cyanide bridged vitamin B₁₂ conjugates with either a cis-[(NH₃)₂Pt]²⁺ or an [enPt]²⁺ moiety, leading to cis-[(NH₃)₂PtCl-vitB₁₂]⁺ (1) and [enPtCl-vitB₁₂]⁺ (2) are reported. The subsequent reaction of cis-[(NH₃)₂PtCl-vitB₁₂]⁺ with the model nucleobase 9-methyladenine leads to the corresponding adduct, where the adenine moiety is coordinated to the Pt²⁺ center either via N1 or N7. This compound is light-stable and harbors the adenine moiety in the same distance of 5 Å above the corrin plane as present in the highly light-sensitive adenosyl cobalamin.     

Growth and development of two polyphagous lepidopterans fed high- and low-tannin sericea lespedeza

The biological impact of consumption of sericea lespedeza (Lespedeza cuneata (Dumont) G. Don) genotypes varying in tannin content was examined for two generalist insect herbivores, Heliothis zea Boddie and Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae). Foliage of high- and lowtannin genotypes did not substantially affect the growth and development of either species when incorporated into meridic diet except at large concentrations where a diet containing high tanin genotypes reduced larval weight and delayed pupation of both species. Fresh foliage of sericea lespedeza with varying levels of tannin did not adversely affect larval growth and development of S. frugiperda. All genotypes were a poor host for H. zea in that most larvae died before pupation. Initial larval weight of H. zea was not consistently different between high- and low-tannin genotypes. Except for one low-tannin genotype having a greater efficiency of conversion of digested diet than the other genotypes, foliage tannin content had little effect on diet assimilation and utilization and larval developmental and consumption rates of stages 6 and 7 H. zea larvae. H. zea neonates also did not show a significant preference for any genotypes. Therefore, tannin content of sericea lespedeza had relatively little effect on the growth and development of these generalist insect defoliators which suggests that low-tannin genotypes of sericea lespedeza will not be substantially more susceptible to defoliation by these species. The poor performance of H. zea on all L. cuneata genotypes suggests that the plant may contain factors other than tannin that inhibit the growth and development of this species or that sericea lespedeza lacks essential nutrients for proper development of H. zea.

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Résumé Les effets de la consommation de phénotypes de la légumineuse S. lespedeza (Lespedeza cuneata) (Dumont) (G. Don) dont les teneurs en tanin diffèrent, ont été examinés sur 2 insectes généralistes; Heliothis zea Boddie et Spodoptera frugiperda (J. E. Smith) (Lep.: Noctuidae). Le feuillage de phénotypes à teneur élevée ou basse en tanin n'a pas affecté considérablement la croissance et le développement des 2 espèces, quand il a été incorporé dans un régime méridique, sauf aux fortes concentrations où un régime contenant le phénotype riche en tanin a réduit le poids larvaire et retardé la nymphose des 2 espèces. Le feuillage frais de S. lespedeza avec différentes teneurs en tanin n'a pas nui au développement et à la croissance larvaire de S. frugiperda. Tous les phénotypes ont constitué un hôte désavantageux pour H. zea dont toutes les chenilles sont mortes avant la nymphose. Les poids initiaux des chenilles de H. zea ne différaient pas significativement suivant la pauvreté ou la richesse en tanin des phénotypes. A l'exception d'un phénotype pauvre en tanin ayant une plus grande efficacité de transformation lors de la digestion, la teneur en tanin du feuillage a eu peu d'effet sur l'assimilation du repas, son utilisation, les taux de consommation et le développement larvaire des stades 6 et 7 des chenilles d'H. zea. Les chenilles néonates de H. zea n'ont présenté aucune préférence significative pour l'un des phénotypes. Par conséquent, la teneur en tanin de S. lespedeza a eu relativement peu d'effet sur la croissance et le développement de ces deux généralistes défoliateurs, ce qui suggère que les phénotypes de S. lespedeza pauvres en tanin ne sont pas nettement plus susceptibles de défoliation par ces espèces. Les faibles performances de H. zea sur tous les phénotypes de S. lespedeza suggèrent que cette plante peut contenir des facteurs autres que les tanins qui inhibent la croissance et le développement de cette espèce ou que S. lespedeza manque de certains éléments nécessaires au développement de H. zea.

     

In vivo covalent binding of aflatoxin B1 and aflatoxin M1 to liver DNA of rat,mouse and pig

[¹⁴C]Aflatoxin B₁ (AFB₁) was isolated from cultures of Aspergillus parasiticus grown on [1-¹⁴C]sodium acetate. Covalent binding of AFB₁ to liver DNA of rat and mouse was determined 6–8 h after oral administration. The effectiveness of covalent binding, expressed as DNA binding per dose in the units of a ‘Covalent Binding Index’ (CBI), (μmol aflatoxin/mol DNA nucleotides)/(mmol aflatoxin/kg animal), was found to be 10 400 for rats and 240 for mice. These CBI partly explain the different susceptibility of the two species for the incidence of hepatic tumors.The corresponding values for pig liver DNA, 24 and 48 h after oral administration, were found to be as high as 19 100 and 13 300. DNA-binding has not so far been reported for this species although it could represent an appropriate animal model for studies where a human-like gastrointestinal tract physiology is desirable.Aflatoxin M₁ (AFM₁) is a metabolite found in the milk of cows that have been fed AFB₁-contaminated diet. [¹⁴C]AFM₁ was also found to be produced by cultures of A. parasiticus giving a yield of about 0.3% of the total aflatoxins. A test for covalent binding to rat liver DNA revealed a CBI of 2100 showing that AFM₁ must also be regarded as a strong hepatocarcinogen. It is concluded that AFB₁ contaminations should be avoided in dairy feed.     

Decrease of aflatoxin B1 in yoghurt and acidified milks

Fermentation of yoghurt and acidified milks containing aflatoxin B₁ (AB₁) were studied. AB₁ added to milk before fermentation at concentrations of 600, 1000 and 1400 g/kg was reduced in yoghurts (pH 4.0) by 97, 91 and 90%, respectively. Coagulation time was approximately the same as in the controls. Streptococci had longer chains than those in the controls. The main decrease of AB₁ occurred during the milk fermentation. A decrease of AB₁ (conc. 1000 g/kg) in milks acidified with citric, lactic and acetic acids (pH 4.0) was 90, 84 and 73%, respectively.     

Reversed-phase high-performance liquid chromatographic method for the determination of the 11-hydroxythromboxane B2 anomers equilibrium

An improved reversed-phase HPLC method for the separation and detection of both hemiacetalic 11-hydroxy anomers of thromboxane B₂ (TXB₂) is described. Water-acetonitrile mixtures have served as mobile phases. By diminishing stepwise the temperature of the chromatographic system from 40 to 0°C, the UV-absorbance profile of TXB₂ changed from one broad peak to two clearly separated narrow peaks corresponding to the two anomers existing in equilibrium. Modification of the mobile phase pH from 1.6 to 6.9 (0°C) resulted in different concentration ratios of the anomers. The equilibrium constant and the Gibbs free energy were calculated. The intermediate open aldehyde form of TXB₂ is unstable and, therefore, cannot be observed either by HPLC or by ¹H NMR measurements.     

Isolation of aflatoxigenic strains of Aspergillus and detection of aflatoxin B1 from feeds in India

In a preliminary study, 256 feed samples collected from different parts of Northern India were examined for the presence of aflatoxigenic strains of Aspergillus flavus/parasiticus and for detection of Aflatoxin B₁ (AFB₁). Out of 198 A. flavus and 15 A. parasiticus strains isolated, 76% and 86% respectively, were found to be toxigenic. Aflatoxin B₁ content of these feeds, as estimated by thin layer chromatography (TLC) and enzyme linked immunosorbent assay (ELISA) were very high (average 0.412 ± 0.154 ppm) in comparison to the permissible Indian regulation level (0.03 ppm). Seasonal variation of incidence and level of toxin in feed was recorded and it was high during monsoon/post monsoon period.This revised version was published online in October 2005 with corrections to the Cover Date.