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János Varga - One of the best experts on this subject based on the ideXlab platform.
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molecular characterization of black aspergillus species from onion and their potential for Ochratoxin a and fumonisin b2 production
Foodborne Pathogens and Disease, 2015Co-Authors: Abdulaziz Bahobial, Bahig El Deeb, Abdulla Altalhi, Sándor Kocsubé, Hesham Elhariry, Youssuf A. Gherbawy, János VargaAbstract:Abstract Onion bulbs can become contaminated with various molds during the storage period, the most important causal agents being black aspergilli (Aspergillus section Nigri). Taxonomic studies have revealed that this group of Aspergillus contains many species that cannot be reliably identified using standard morphological methods. Therefore, it is necessary to define the fungus causing this problem in the onion exactly, especially since some species assigned to section Nigri are well known as Ochratoxin and/or fumonisin producers. Sixty fungal isolates belonging to 10 fungal genera were isolated from 40 onion samples originated from the Taif region in Saudi Arabia. Black aspergilli were detected in 37 onion samples. Using primer pairs (awaspec and Cmd6) designed based on partial calmodulin gene sequence data, 37 isolates were identified as A. welwitschiae. The Ochratoxin A and fumonisin B2 contents of the onion samples were examined. No Ochratoxins were detected in the collected samples, while fumonisin ...
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fumonisin and Ochratoxin production in industrial aspergillus niger strains
PLOS ONE, 2011Co-Authors: Jens Christian Frisvad, János Varga, Thomas Ostenfeld Larsen, Ulf Thrane, M Meijer, Robert A Samson, Kristian Fog NielsenAbstract:Aspergillus niger is perhaps the most important fungus used in biotechnology, and is also one of the most commonly encountered fungi contaminating foods and feedstuffs, and occurring in soil and indoor environments. Many of its industrial applications have been given GRAS status (generally regarded as safe). However, A. niger has the potential to produce two groups of potentially carcinogenic mycotoxins: fumonisins and Ochratoxins. In this study all available industrial and many non-industrial strains of A. niger (180 strains) as well as 228 strains from 17 related black Aspergillus species were examined for mycotoxin production. None of the related 17 species of black Aspergilli produced fumonisins. Fumonisins (B2, B4, and B6) were detected in 81% of A. niger, and Ochratoxin A in 17%, while 10% of the strains produced both mycotoxins. Among the industrial strains the same ratios were 83%, 33% and 26% respectively. Some of the most frequently used strains in industry NRRL 337, 3112 and 3122 produced both toxins and several strains used for citric acid production were among the best producers of fumonisins in pure agar culture. Most strains used for other biotechnological processes also produced fumonisins. Strains optimized through random mutagenesis usually maintained their mycotoxin production capability. Toxigenic strains were also able to produce the toxins on media suggested for citric acid production with most of the toxins found in the biomass, thereby questioning the use of the remaining biomass as animal feed. In conclusion it is recommended to use strains of A. niger with inactive or inactivated gene clusters for fumonisins and Ochratoxins, or to choose isolates for biotechnological uses in related non-toxigenic species such as A. tubingensis, A. brasiliensis, A vadensis or A. acidus, which neither produce fumonisins nor Ochratoxins.
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Mycobiota and Ochratoxin A in raisins purchased in Hungary
Acta Alimentaria, 2006Co-Authors: János Varga, Sándor Kocsubé, Z. Koncz, József TérenAbstract:Ochratoxin A is a mycotoxin produced by Aspergillus and Penicillium species. This mycotoxin is a common contaminant of various foods including cereal products, spices, dried fruits, coffee, beer and wine. Besides cereal products, goods of grape origin contribute significantly to Ochratoxin exposure of humans. The Ochratoxin content and mycobiota of raisins purchased in Hungarian outlets were examined in this study. Ochratoxin A content was examined by an immunochemical technique, and the results were confirmed by HPLC analysis using fluorescent detection. Altogether 20 raisin samples were analyzed. Ochratoxin A was detected in all but two samples with Ochratoxin concentrations ranging from 0 to 6.2 mg kg-1. The most heavily contaminated raisin sample came from Iran. However, none of the raisins contained Ochratoxin A above 10 mg kg-1, the European Community maximum allowable limit in raisins. The mycobiota of raisin samples was also examined to clarify which species could be responsible for Ochratoxin A c...
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Ochratoxin A in grapes and grape-derived products
Trends in Food Science and Technology, 2006Co-Authors: János Varga, Zofia KozakiewiczAbstract:Ochratoxin A is a nephrotoxic compound which was first detected in wine in the nineties. Since then, several grape-derived products have been found to be potentially contaminated. Ochratoxin contamination of grapes takes place in the field and is caused mainly by black Aspergilli, especially A. carbonarius. Several factors affect Ochratoxin production by black Aspergilli on grapes. Attempts have been made to lower fungal contamination and thereby Ochratoxin contamination of grapes, with varying success. This review attempts to give an overview of our recent knowledge regarding the occurrence and detection of, and legislation for Ochratoxins in grapes and grape-derived products. We will also discuss the potential sources of Ochratoxin contamination, and possible strategies for control of Ochratoxins in wines and other grape products.
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Detection of Ochratoxin A in Hungarian Wines and Beers
Acta Alimentaria, 2005Co-Authors: János Varga, R. Kiss, T. Mátrai, József TérenAbstract:Ochratoxin A is a mycotoxin produced by Aspergillus and Penicillium species. This mycotoxin is a common contaminant of various food products including cereal products, spices, dried fruits, coffee, beer and wine. Besides cereal products, beer and wine contribute significantly to Ochratoxin exposure of humans. We examined the Ochratoxin content of Hungarian wines and beers using an immunochemical technique. The detection limit of this technique is 0.01 μg l –1 . Altogether 65 wine and 25 beer samples were analysed. The presence of Ochratoxin A was confirmed by HPLC in positive samples. Ochratoxin A was detected in 97.7% of wines, with Ochratoxin concentrations ranging from 0 to 0.533 μg l –1 . The mean ochra toxin A concentration in wines was 0.110 μg l –1 . Only one of the Hungarian wines examined contained more than 0.5 μg l –1 Ochratoxin A, the previously suggested EU limit for wine. Our data indicate that red wines are more frequently contaminated, and have h igher mean Ochratoxin contamination (0.117 μg ml –1 ) than white wines (0.0967 μg ml –1 ), in accordance with previous observations. A North -South gradient in wine Ochratoxin concentrations is not evident from our data. For beers, all but one of the samples wa s found to be contaminated with small amounts of Ochratoxin A with a mean concentration of 0.127 μg l –1 (range: 0.030 –0.250 μg l –1 ). Only one of the beers contained Ochratoxin A above 0.2 μg l –1 , the anticipated European Community maximum allowable limit i n beer. We could not detect correlation between the type and origin of beer and Ochratoxin contamination.
Hans-ulrich Humpf - One of the best experts on this subject based on the ideXlab platform.
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Structure elucidation and in vitro cytotoxicity of Ochratoxin α amide, a new degradation product of Ochratoxin A
Mycotoxin Research, 2015Co-Authors: Andrea Bittner, Benedikt Cramer, Henning Harrer, Hans-ulrich HumpfAbstract:The mycotoxin Ochratoxin A is a secondary metabolite occurring in a wide range of commodities. During the exposure of Ochratoxin A to white and blue light, a cleavage between the carbon atom C-14 and the nitrogen atom was described. As a reaction product, the new compound Ochratoxin α amide has been proposed based on mass spectrometry (MS) experiments. In the following study, we observed that this compound is also formed at high temperatures such as used for example during coffee roasting and therefore represents a further thermal Ochratoxin A degradation product. To confirm the structure of Ochratoxin α amide, the compound was prepared in large scale and complete structure elucidation via nuclear magnetic resonance (NMR) and MS was performed. Additionally, first studies on the toxicity of Ochratoxin α amide were performed using immortalized human kidney epithelial (IHKE) cells, a cell line known to be sensitive against Ochratoxin A with an IC_50 value of 0.5 μM. Using this system, Ochratoxin α amide revealed no cytotoxicity up to concentrations of 50 μM. Thus, these results propose that the thermal degradation of Ochratoxin A to Ochratoxin α amide might be a detoxification process. Finally, we present a sample preparation and a HPLC-tandem mass spectrometry (HPLC-MS/MS) method for the analysis of Ochratoxin α amide in extrudates and checked its formation during the extrusion of artificially contaminated wheat grits at 150 and 180 °C, whereas no Ochratoxin α amide was detectable under these conditions.
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Matrix binding of Ochratoxin A during roasting.
Journal of Agricultural and Food Chemistry, 2013Co-Authors: Andrea Bittner, Benedikt Cramer, Hans-ulrich HumpfAbstract:The mycotoxin Ochratoxin A is degraded during coffee roasting by up to 90%. During this process, the two known degradation products, 14R-Ochratoxin A and 14-decarboxy-Ochratoxin A are formed. However, there is still an unexplained loss of more than 50% Ochratoxin A. Here, we describe the binding of Ochratoxin A to coffee polysaccharides via esterification as a further thermal reaction. This ester formation was studied by heating Ochratoxin A with methyl α-d-glucopyranoside, a model compound to mimic polysaccharides. From this experiment, (22 → 6′) Ochratoxin A-methyl-α-d-glucopyranoside ester was isolated and characterized as a reaction product, showing the general ability of Ochratoxin A for esterification with carbohydrates at roasting temperatures. Subsequently, a sample preparation protocol for the detection of Ochratoxin A saccharide esters based on an enzymatic cleavage and purification using immunoaffinity chromatography was developed and applied. The detection was carried out by high-performance l...
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identification and in vitro cytotoxicity of Ochratoxin a degradation products formed during coffee roasting
Journal of Agricultural and Food Chemistry, 2008Co-Authors: Benedikt Cramer, Maika Konigs, Hans-ulrich HumpfAbstract:The mycotoxin Ochratoxin A is degraded by up to 90% during coffee roasting. In order to investigate this degradation, model heating experiments with Ochratoxin A were carried out, and the reaction products were analyzed by HPLC-DAD and HPLC-MS/MS. Two Ochratoxin A degradation products were identified, and their structure and absolute configuration were determined. As degradation reactions, the isomerization to 14-(R)-Ochratoxin A and the decarboxylation to 14-decarboxy-Ochratoxin A were identified. Subsequently, an analytical method for the determination of these compounds in roasted coffee was developed. Quantification was carried out by HPLC-MS/MS and the use of stable isotope dilution analysis. By using this method for the analysis of 15 coffee samples from the German market, it could be shown that, during coffee roasting, the Ochratoxin A diastereomer 14-(R)-Ochratoxin A was formed in amounts of up to 25.6% relative to Ochratoxin A. The decarboxylation product was formed only in traces. For toxicity e...
Benedikt Cramer - One of the best experts on this subject based on the ideXlab platform.
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Structure elucidation and in vitro cytotoxicity of Ochratoxin α amide, a new degradation product of Ochratoxin A
Mycotoxin Research, 2015Co-Authors: Andrea Bittner, Benedikt Cramer, Henning Harrer, Hans-ulrich HumpfAbstract:The mycotoxin Ochratoxin A is a secondary metabolite occurring in a wide range of commodities. During the exposure of Ochratoxin A to white and blue light, a cleavage between the carbon atom C-14 and the nitrogen atom was described. As a reaction product, the new compound Ochratoxin α amide has been proposed based on mass spectrometry (MS) experiments. In the following study, we observed that this compound is also formed at high temperatures such as used for example during coffee roasting and therefore represents a further thermal Ochratoxin A degradation product. To confirm the structure of Ochratoxin α amide, the compound was prepared in large scale and complete structure elucidation via nuclear magnetic resonance (NMR) and MS was performed. Additionally, first studies on the toxicity of Ochratoxin α amide were performed using immortalized human kidney epithelial (IHKE) cells, a cell line known to be sensitive against Ochratoxin A with an IC_50 value of 0.5 μM. Using this system, Ochratoxin α amide revealed no cytotoxicity up to concentrations of 50 μM. Thus, these results propose that the thermal degradation of Ochratoxin A to Ochratoxin α amide might be a detoxification process. Finally, we present a sample preparation and a HPLC-tandem mass spectrometry (HPLC-MS/MS) method for the analysis of Ochratoxin α amide in extrudates and checked its formation during the extrusion of artificially contaminated wheat grits at 150 and 180 °C, whereas no Ochratoxin α amide was detectable under these conditions.
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Matrix binding of Ochratoxin A during roasting.
Journal of Agricultural and Food Chemistry, 2013Co-Authors: Andrea Bittner, Benedikt Cramer, Hans-ulrich HumpfAbstract:The mycotoxin Ochratoxin A is degraded during coffee roasting by up to 90%. During this process, the two known degradation products, 14R-Ochratoxin A and 14-decarboxy-Ochratoxin A are formed. However, there is still an unexplained loss of more than 50% Ochratoxin A. Here, we describe the binding of Ochratoxin A to coffee polysaccharides via esterification as a further thermal reaction. This ester formation was studied by heating Ochratoxin A with methyl α-d-glucopyranoside, a model compound to mimic polysaccharides. From this experiment, (22 → 6′) Ochratoxin A-methyl-α-d-glucopyranoside ester was isolated and characterized as a reaction product, showing the general ability of Ochratoxin A for esterification with carbohydrates at roasting temperatures. Subsequently, a sample preparation protocol for the detection of Ochratoxin A saccharide esters based on an enzymatic cleavage and purification using immunoaffinity chromatography was developed and applied. The detection was carried out by high-performance l...
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identification and in vitro cytotoxicity of Ochratoxin a degradation products formed during coffee roasting
Journal of Agricultural and Food Chemistry, 2008Co-Authors: Benedikt Cramer, Maika Konigs, Hans-ulrich HumpfAbstract:The mycotoxin Ochratoxin A is degraded by up to 90% during coffee roasting. In order to investigate this degradation, model heating experiments with Ochratoxin A were carried out, and the reaction products were analyzed by HPLC-DAD and HPLC-MS/MS. Two Ochratoxin A degradation products were identified, and their structure and absolute configuration were determined. As degradation reactions, the isomerization to 14-(R)-Ochratoxin A and the decarboxylation to 14-decarboxy-Ochratoxin A were identified. Subsequently, an analytical method for the determination of these compounds in roasted coffee was developed. Quantification was carried out by HPLC-MS/MS and the use of stable isotope dilution analysis. By using this method for the analysis of 15 coffee samples from the German market, it could be shown that, during coffee roasting, the Ochratoxin A diastereomer 14-(R)-Ochratoxin A was formed in amounts of up to 25.6% relative to Ochratoxin A. The decarboxylation product was formed only in traces. For toxicity e...
Kristian Fog Nielsen - One of the best experts on this subject based on the ideXlab platform.
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fumonisin and Ochratoxin production in industrial aspergillus niger strains
PLOS ONE, 2011Co-Authors: Jens Christian Frisvad, János Varga, Thomas Ostenfeld Larsen, Ulf Thrane, M Meijer, Robert A Samson, Kristian Fog NielsenAbstract:Aspergillus niger is perhaps the most important fungus used in biotechnology, and is also one of the most commonly encountered fungi contaminating foods and feedstuffs, and occurring in soil and indoor environments. Many of its industrial applications have been given GRAS status (generally regarded as safe). However, A. niger has the potential to produce two groups of potentially carcinogenic mycotoxins: fumonisins and Ochratoxins. In this study all available industrial and many non-industrial strains of A. niger (180 strains) as well as 228 strains from 17 related black Aspergillus species were examined for mycotoxin production. None of the related 17 species of black Aspergilli produced fumonisins. Fumonisins (B2, B4, and B6) were detected in 81% of A. niger, and Ochratoxin A in 17%, while 10% of the strains produced both mycotoxins. Among the industrial strains the same ratios were 83%, 33% and 26% respectively. Some of the most frequently used strains in industry NRRL 337, 3112 and 3122 produced both toxins and several strains used for citric acid production were among the best producers of fumonisins in pure agar culture. Most strains used for other biotechnological processes also produced fumonisins. Strains optimized through random mutagenesis usually maintained their mycotoxin production capability. Toxigenic strains were also able to produce the toxins on media suggested for citric acid production with most of the toxins found in the biomass, thereby questioning the use of the remaining biomass as animal feed. In conclusion it is recommended to use strains of A. niger with inactive or inactivated gene clusters for fumonisins and Ochratoxins, or to choose isolates for biotechnological uses in related non-toxigenic species such as A. tubingensis, A. brasiliensis, A vadensis or A. acidus, which neither produce fumonisins nor Ochratoxins.
Thomas Ostenfeld Larsen - One of the best experts on this subject based on the ideXlab platform.
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fumonisin and Ochratoxin production in industrial aspergillus niger strains
PLOS ONE, 2011Co-Authors: Jens Christian Frisvad, János Varga, Thomas Ostenfeld Larsen, Ulf Thrane, M Meijer, Robert A Samson, Kristian Fog NielsenAbstract:Aspergillus niger is perhaps the most important fungus used in biotechnology, and is also one of the most commonly encountered fungi contaminating foods and feedstuffs, and occurring in soil and indoor environments. Many of its industrial applications have been given GRAS status (generally regarded as safe). However, A. niger has the potential to produce two groups of potentially carcinogenic mycotoxins: fumonisins and Ochratoxins. In this study all available industrial and many non-industrial strains of A. niger (180 strains) as well as 228 strains from 17 related black Aspergillus species were examined for mycotoxin production. None of the related 17 species of black Aspergilli produced fumonisins. Fumonisins (B2, B4, and B6) were detected in 81% of A. niger, and Ochratoxin A in 17%, while 10% of the strains produced both mycotoxins. Among the industrial strains the same ratios were 83%, 33% and 26% respectively. Some of the most frequently used strains in industry NRRL 337, 3112 and 3122 produced both toxins and several strains used for citric acid production were among the best producers of fumonisins in pure agar culture. Most strains used for other biotechnological processes also produced fumonisins. Strains optimized through random mutagenesis usually maintained their mycotoxin production capability. Toxigenic strains were also able to produce the toxins on media suggested for citric acid production with most of the toxins found in the biomass, thereby questioning the use of the remaining biomass as animal feed. In conclusion it is recommended to use strains of A. niger with inactive or inactivated gene clusters for fumonisins and Ochratoxins, or to choose isolates for biotechnological uses in related non-toxigenic species such as A. tubingensis, A. brasiliensis, A vadensis or A. acidus, which neither produce fumonisins nor Ochratoxins.
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biochemical characterization of Ochratoxin a producing strains of the genus penicillium
Applied and Environmental Microbiology, 2001Co-Authors: Thomas Ostenfeld Larsen, Anne Svendsen, Jorn SmedsgaardAbstract:In order to explore the biochemical scope of Ochratoxin A-producing penicillia, we screened 48 Penicillium verrucosum isolates for the production of secondary metabolites. Fungal metabolites were analyzed by high-pressure liquid or gas chromatography coupled to diode array detection or mass spectrometry. The following metabolites were identified: Ochratoxins A and B, citrinin, verrucolones, verrucines, anacines, sclerotigenin, lumpidin, fumiquinazolines, alantrypinones, daldinin D, dipodazine, penigequinolines A and B, 2-pentanone, and 2-methyl-isoborneol. By use of average linking clustering based on binary (nonvolatile) metabolite data, the 48 isolates could be grouped into two large and clearly separated groups and a small outlying group of four non-Ochratoxin-producing isolates. The largest group, containing 24 isolates, mainly originating from plant sources, included the type culture of P. verrucosum. These isolates produced Ochratoxin A, verrucolones, citrinin, and verrucines and had a characteristic dark brown reverse color on yeast extract-sucrose agar medium. Almost all of a group of 20 isolates mainly originating from cheese and meat products had a pale cream reverse color on yeast extract-sucrose agar medium and produced Ochratoxin A, verrucolones, anacines, and sclerotigenin. This group included the former type culture of P. nordicum. We also found that P. verrucosum isolates and three P. nordicum isolates incorporated phenylalanine into verrucine and lumpidin metabolites, a finding which could explain why those isolates produced relatively lower levels of Ochratoxins than did most isolates of P. nordicum.
