1,721,011 research outputs found
Aflatoxin and ochratoxin in cereal grains: An open challenge
No full textThe environmental, physiological and molecular factors related with aflatoxin and ochratoxin production by fungal species are reviewed. Concerning aflatoxins, the main steps that have lead to the knowledge of their biosynthesis gene cluster are reported and the experimental work that has allowed to determine different control strategies is underlined. Concerning ochratoxins, the biosynthetic pathway and the main implications in animal and human toxicity are presented. The role played by lipoperoxides in the secondary metabolism and toxin production is emphasized. A view of the different control system through prevention, decontamination and detoxification is described. The importance of preventive strategies (physical, chemical, biological and genetic approaches) in the control of such widespread and toxic metabolites is pointed out
DETECTION OF OCHRATOXIGENIC ASPERGILLI ON GRAPE BERRIES DURING DRYING FOR PRODUCTION OF “VIN SANTO”
No full textAspergillus carbonarius, A. niger and A. tubingensis are known to produce ochratoxin A (OTA), a secondary metabolite with very dangerous effects to animals and humans. The International Agency for Research on Cancer has classified OTA as a possible carcinogen to humans (group 2B). As a consequence, the European Commission has imposed regulatory limits for the maximum tolerable presence of this toxin in different foodstuffs. After cereals, grape products are accounted as a considerable source of human OTA intake. Based on the fungal requirements of environmental temperature and relative humidity, it is easy to suppose that wines, as the Tuscan “Vin Santo”, obtained from grapes partially dried for several months to concentrate sugar content to at least 30% (w/v), are potentially at risk more than table wines. In the present work, done in the “Azienda Agricola Montepaldi” (San Casciano Val di Pesa, Florence), we isolated from grape berries about 6x107 CFU, divided into six major fungal morphotypes. Among these 24 were typical colonies of Aspergillus spp. These colonies were processed in parallel using: (i) conventional culture methods that allowed their morphological description; (ii) a molecular approach based on sequencing of the internal transcribed spacer (ITS) region comprising the ITS1, the ITS2, and the intervening 5.8S rRNA gene. Due to the known high intraand interspecific variability of the ITS region, it was not difficult to identify the fungal morphotypes isolated from the berries. The Aspergilli belonged to the species A. tubingensis. Analysis to find isolates producing OTA is ongoing
INHIBITING EFFECT OF DIFFERENT EDIBLE AND MEDICINAL MUSHROOMS ON THE GROWTH OF TWO OCHRATOXIGENIC MICROFUNGI.
No full textThe efficacy of different antioxidant and antimicrobial substances on the growth of two ochratoxigenic fungi has been investigated. Among the compounds used are some edible and medicinal higher Basidiomycetes mushrooms, Lentinus edodes (Berk.) Sing., Agrocybe aegerita (Brig.) Sing., and Pleurotus eryngii (DC.: Fr) Quel., whose antimicrobial and antioxidant properties have already been reported. The experimental results obtained indicate that some antioxidants and some edible and medicinal mushroom extracts can inhibit the growth of the two tested toxigenic microfungi species, Aspergillus ochraceus and Penicillium verrucosum
Inhibiting effect of medicinal mushrooms Lentinus edodes (Berk.) Sing. (Agaricomycetideae) on aflatoxin production by Aspergillus parasiticus Speare.
No full textCulture filtrates of Lentinus edodes (Berk.) Sing, (shiitake mushroom) added to potato dextrose broth inoculated with a toxigenic strain of Aspergillus parasiticus Speare showed an inhibiting effect on aflatoxin production. Filtrates from 30- (steady conditions) and 15-(shaken conditions)-day-old cultures were the most efficient in inhibiting aflatoxin production by A. parasiticus. Mycelia of L. edodes, incubated on wheat seeds for 20 and 30 days and subsequently inoculated with A. parasiticus, delayed fungal growth of the toxigenic strain and inhibited aflatoxin production. L. edodes represents a promising medicinal mushroom to control the infection by A. parasiticus and the aflatoxin production
Antioxidant enzymes stimulation in Aspergillus parasiticus by Lentinula edodes inhibits aflatoxin production
No full textBiosynthesis of aflatoxins, toxic metabolites produced by Aspergillusparasiticus, is correlated to the fungal oxidative stress and cell ageing. In this paper, the mechanism underlying the aflatoxin-inhibiting effect of the Lentinula edodes culture filtrates was studied by analysing their anti-oxidant activity and beta-glucan content. Mushroom beta-glucans are pharmacologically active compounds stimulating anti-oxidant responses in animal cells. L. edodes lyophillsed filtrates stimulate A. parasiticus anti-oxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase) and aflatoxin inhibition was better correlated with beta-glucan content than with anti-oxidant activity of the filtrates. RT-PCR analyses on treated mycelia showed a delay in the activation of aflR, and norA, genes of aflatoxin cluster and a synchronous activation of hsf2-like, a homologue of a yeast transcription factor involved in oxidative stress responses. The first evidence of hsf2-like in A. parasiticus and its activation during aflatoxin biosynthesis is reported. L. edodes filtrates could play a role as external stimulus affecting the anti-oxidant status in the fungal cell that, in turn, leads to aflatoxin inhibition. In the fungal cell, beta-glucans present in the filtrates could stimulate the activation of transcription factors related to anti-oxidant response and anti-oxidant enzyme activity with a contemporaneous delay of aflatoxin genes transcription, which led to a marked reduction of aflatoxin production. This research suggests new perspectives to set suitable strategies against aflatoxins and L. edodes could be considered a promising tool
Study of some physiological and molecular alterations induced by Italian strains of Alternaria alternata in two varieties of apple fruit.
No full textEARLY DETECTION OF TOXIGENIC FUNGI ON MAIZE KERNELS BY SPECTRAL IMAGING ANALYSIS.
No full textMaize (Zea mays L.) is an important cereal, used for food and for animal feed. Several toxigenic fungi can infect maize in the field and in the post harvest conditions. In particular, maize is susceptible to infection by fungi belonging to Fusarium and Aspergillus. Several studies have assayed non-destructive, spectral methods to detect fungal contamination and toxins on cereals. The aim of this work is the early detection of toxigenic fungi on whole maize kernels, the discrimination between healthy and diseased kernels and the determination of damage degree by using a Spectral Imaging -based method. A desktop spectral scanner equipped with an imaging based spectrometer ImSpector-Specim V10, working in the visible-near infrared spectral range (400-1000 nm) was used in the esperiments. Four pure toxigenic fungal strains were imaged, A. parasiticus, A. flavus, A. niger and F. graminearum. The results obtained indicate that spectral imaging can discriminate between different fungal strains, producing a specific spectral fingerprint for each one. These fungi have been also inoculated on maize kernels and were imaged from 24 h to 7 days of growth. Changes in reflectance of kernels were observed during fungal growth. Spectral imaging could be able to discriminate maize kernels infected with toxigenic fungi from uninfected controls; this technique could be used for an early detection of toxigenic fungi on cereals
Lentinula edodes: a possibile tool in the challenge against mycotoxins.
No full textLentinula edodes (Berk) Pegler is an edible mushroom widely cultivated in the Asian countries. This basidiomycete is also known for the production of different substances, mainly b-glucans, with healing effects on animals and humans. Some of these substances can also be released into the culture media. The effects of lyophilised L. edodes filtrates on conidia germination of different isolates of Aspergillus spp., Fusarium spp. and Penicillium spp., and the production of some mycotoxins like aflatoxins (B1, B2, G1, G2), ochratoxin A, fumonisins (B1, B2) and zearalenone were tested. The addition of lyophilised filtrates showed some inhibiting effect on conidia germination (10-40%) of all toxigenic strains assayed. The presence of lyophilised filtrates severely affected mycotoxin production. The inhibition (40 to 90%) was in relation both to the toxigenic strain examined and the L. edodes isolate used. The filtrates of a same L. edodes isolate grown on different media showed similar aflatoxin inhibiting capacity, indicating that the toxin control is due to some strain-dependent metabolic product. Furthermore the isolate CF 42 resulted the most efficient in the control of all mycotoxins assayed. Antioxidant activity was detected, using the crocin test, in all filtrates. The results obtained indicate that L. edodes produces substance/ s able to control the synthesis of different mycotoxins probably by a similar mechanism. Considering the healing properties and low citotoxicity of L. edodes metabolites and their capacity to control several toxins this mushroom could represent an important tool in the challenge against mycotoxins especially in animal feed industry
Oxidant/antioxidant balance inAspergillus parasiticus affects aflatoxin biosynthesis.
No full textA close correlation between lipoperoxide formation in cells ofAspergillus parasiticus and aflatoxin biosynthesis has been established in rich and poor media in which oxidative stress was induced by addition of cumene hydroperoxide, a lipoperoxidation inducer. The presence of hydroperoxides of linoleic acid inA. parasiticus mycelia was analysed by liquid chromatography-mass spectrometry (LC-MS). This relation appears to be driven by activation of certain oxidative stress related transcription factors, such asyap1-like,skn7-like andhsf2-like. Activation of these factors then leads to the promotion of transcription of genes encoding antioxidant-related enzymes, such as superoxide dismutase, catalase and glutathione peroxidase.The incomplete seavenging of intracellular oxidation inA. parasiticus cells can lead to aflatoxin biosynthesis. The relationship between oxidative stress and aflatoxin biosynthesis is indicated by the high correlation among increased activity of lipoperoxidation and the antioxidant defence system with formation of aflatoxins.With regard to the relationship of oxidative stress and aflatoxin biosynthesis, the mechanism of action of butylated hydroxyl anisole (BHA), an antioxidant compound, in the control of aflatoxin biosynthesis was also investigated. Results indicate this compound can act,per se, by inhibiting lipoperoxidation and by inducing antioxidative defence responses of the fungal cell
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