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You searched for subject:(Aspergillus westerdijkiae). Showing records 1 – 3 of 3 total matches.

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1. Meftah, Sana. Effect of commercial starter cultures and native yeasts on ochratoxin a production by aspergillus westerdijkiae and penicillium nordicum in meat products.

Degree: 2015, Instituto Politécnico de Bragança

Processed meat products are of worldwide importance and, because of their intrinsic factors as well as the processing methods, they are highly prone to fungal and mycotoxin contamination. Ochratoxin A (OTA) is the most significant mycotoxin in processed meat products. Penicillium nordicum is considered to be responsible for OTA contamination of meat products, as it is highly adapted to salt and protein-rich matrices and is moderately psycrotrophic. However, another OTA-producing fungus, Aspergillus westerdijkiae, adapted to carbon-rich matrices such as cereals and coffee beans, has been recently associated with high levels of OTA in meat products. Several Lactic Acid Bacteria (LAB) and yeasts have been tested as biocontrol agents against P. nordicum growth and OTA production in meat products, with promising results, but none of the studies have considered A. westerdijkiae. The aim of this work was to evaluate in vitro the effect of a commercial starter culture used in sausage fermentation and four yeasts isolated from dry-cured sausage on these two OTA-producing fungi, both in terms of fungal growth and of OTA production, using different meat-based culture media as model systems. The mechanisms underlying the observed effect were also studied. For this purpose, C. krusei, C. zeylanoides, R. mucilaginosa, R. glutinis, a mix of these yeasts and the starter culture were co-inoculated with P. nordicum and A. westerdijkiae in industrial sausage, traditional sausage, and ham-based media, under conditions of water activity, salt concentration and temperature that mimic real conditions at beginning and end of sausage curing process. Fungal growth was determined by measuring colony diameter, and OTA production was quantified by HPLC-FLD after extraction with methanol. Yeasts where found to inhibit significantly the growth of both fungi. P. nordicum was unable to produce detectable OTA in both sausage-based media under any condition. In ham, yeasts reduced OTA production, while the starter culture significantly increased it. Unexpectedly, OTA production by A. westerdijkiae was significantly stimulated in all media tested by all microorganisms. Matrix has a significant effect on OTA production by P. nordicum, but not by A. westerdijkiae, for which only temperature showed to have effect. By testing the mechanisms of action by which starter culture and C. zeylanoides influenced fungal responses, we were able to determine that direct contact and simultaneous growth of test organisms were the mechanisms more significantly involved in the responses. In conclusion, ochratoxigenic fungi do not all respond to antagonistic microorganisms in the same way. The use of biocontrol agents with the intent of reducing fungal growth and mycotoxin production by one fungus can have unexpected effects on others, thus leading to unforeseen safety problems. Further experiments are recommended to properly understand the reasons behind the different effects of microorganisms, to ensure their safe as biocontrol agents.

Os produtos processados de…

Advisors/Committee Members: Rodrigues, Paula, Dias, Teresa, Abid, Salwa.

Subjects/Keywords: Mycotoxins; Aspergillus westerdijkiae; Penicillium nordicum; HPLC-FLD; Yeast; Starter culture; Domínio/Área Científica::Ciências Agrárias::Biotecnologia Agrária e Alimentar

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APA (6th Edition):

Meftah, S. (2015). Effect of commercial starter cultures and native yeasts on ochratoxin a production by aspergillus westerdijkiae and penicillium nordicum in meat products. (Thesis). Instituto Politécnico de Bragança. Retrieved from https://www.rcaap.pt/detail.jsp?id=oai:bibliotecadigital.ipb.pt:10198/13143

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Meftah, Sana. “Effect of commercial starter cultures and native yeasts on ochratoxin a production by aspergillus westerdijkiae and penicillium nordicum in meat products.” 2015. Thesis, Instituto Politécnico de Bragança. Accessed January 16, 2021. https://www.rcaap.pt/detail.jsp?id=oai:bibliotecadigital.ipb.pt:10198/13143.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Meftah, Sana. “Effect of commercial starter cultures and native yeasts on ochratoxin a production by aspergillus westerdijkiae and penicillium nordicum in meat products.” 2015. Web. 16 Jan 2021.

Vancouver:

Meftah S. Effect of commercial starter cultures and native yeasts on ochratoxin a production by aspergillus westerdijkiae and penicillium nordicum in meat products. [Internet] [Thesis]. Instituto Politécnico de Bragança; 2015. [cited 2021 Jan 16]. Available from: https://www.rcaap.pt/detail.jsp?id=oai:bibliotecadigital.ipb.pt:10198/13143.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Meftah S. Effect of commercial starter cultures and native yeasts on ochratoxin a production by aspergillus westerdijkiae and penicillium nordicum in meat products. [Thesis]. Instituto Politécnico de Bragança; 2015. Available from: https://www.rcaap.pt/detail.jsp?id=oai:bibliotecadigital.ipb.pt:10198/13143

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


INP Toulouse

2. Bacha, Nafees. Caractérisation des polycétones synthases intervenant dans la biosynthèse d’ochratoxine A, d’acide pénicillique, d’asperlactone et d’isoasperlactone chez aspergillus westerdijkiae : Caracterization of the polyketide synthases involved in biosynthesis of ochratoxin A, penicillic acid, asperlactone and isoasperlactone in aspergillus westerdijkiae (a molecular approach).

Degree: Docteur es, Microbiologie et biocatalyse industrielles, 2009, INP Toulouse

Aspergillus westerdijkiaem qui est récemment démembré d'A. ochraceus est un producteur principal de plusieurs composés de type polycétone d'importance économique. Ces composés incluent l’ochratoxin A, mellein, l'acide penicillique, asperlactone et l’isoasperlactone et quelques intermédiaires comme l'acide 6- methylsalicylique et l’acide orsellinique. La biosynthèse de ces métabolites est catalysée par un groupe d'enzymes connues comme la polycétone synthases (PKSs). Ce travail a été visé pour cloner et a caractérisé fonctionnellement les différentes genes des PKS i.e. aoks1, aolc35-12 et aomsas, et de genes de polyketide synthases-non ribosomal peptide synthase (PKS-NRPS) i.e. aolc35-6, chez A. westerdijkiae. Ces gènes ont été inactivés par l'insertion du gène d’hygromycine B phosphotransferase d’Escherichia coli dans le génome d'A. westerdijkiae, pour obtenir les mutantes ao?ks1, ao?lc35-12, ao?msas et ao?lc35-6. Les mutants ao?ks1 et ao?lc35-12 ont été trouvés déficients dans la biosynthèse d’ochratoxin A, mais produisaient encore mellein. À notre connaissance, c’est la première fois que nous avons caractérisé les gènes impliquées dans la biosynthèse d’OTA, sachant que mellein, qui était proposé dans la littérature comme un intermédiaire, joue a cune role dans la biosynthesis de l'OTA. Ensuite le mutant ao?msas n'a pas seulement perdu la capacité de produire isoasperlactone et asperlactone, mais aussi il ne produit pas l’intermédiaire acide 6-methylsalicylique. Basé sur les expériences de la caractérisation génétique et de complémentation chimiques, nous avons proposé un shéma hypothétique de la biosynthèse d’asperlactone et isoasperlactone dans lequel l'acide 6-methylsalicylique, diepoxide et aspyrone jouent le rôle d’intermédiaires. La techniques de gène knock-out et de la reverse transcription PCR (RT-PCR) ont montré que seulle gène de type PKS-NRPS « aolc35-6 » identifié chez A. westerdijkiae codant pour un intermédiaire inconnu(s) qui pourrait inciter l'expression de gène aomsas et un gène impliqué dans la biosynthèse d'acide orsellinique et d'acide penicillique.

Aspergillus westerdijkiaem which is recently dismembered from A. ochraceusm is the principal producer of several economically important polyketide metabolites. These metabolites include ochratoxin A, mellein, penicillic acid, asperlactone and isoasperlactone and some intermediates like orsellinic acid and 6-methylsalicylic acid. The biosynthesis of these metabolites is catalyzed by a group of enzymes known as polyketide synthases (PKSs). This work was aimed to clone and functionally characterized various PKS i.e. aoks1, aolc35-12 and aomsas, and polyketide synthasesnon ribosomal peptide synthase (PKS-NRPS) genes i.e. aolc35-6, in A. westerdijkiae. These genes were inactivated by the insertion of Escherichia coli hygromycin B phosphotransferase gene in the genome of A. westerdijkiae to obtain ao?ks1, ao?lc35-12, ao?msas and ao?lc35-6 mutants. ao?ks1, ao?lc35-12 mutants were found deficient in ochratoxin A biosynthesis but are still producing…

Advisors/Committee Members: Lebrihi, Ahmed (thesis director), Mathieu, Florence (thesis director).

Subjects/Keywords: Aspergillus westerdijkiae; Polycétone synthase gènes; Caractérisation génétique; Genome walking; Transformation; Complémentation chimique; Ochratoxine A; Acide penicillique; Aspyrone; Acide 6-methylsalicylique; Isoasperlactone; Asperlactone; Aspergillus westerdijkiae; Polyketide synthase genes; Genetic characterization; Genome calking; Transformation; Chemical complementation; Ochratoxin A; Penicillic acid; Aspyrone; 6-methylsalicylic acid; Isoasperlactone; Asperlactone

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Bacha, N. (2009). Caractérisation des polycétones synthases intervenant dans la biosynthèse d’ochratoxine A, d’acide pénicillique, d’asperlactone et d’isoasperlactone chez aspergillus westerdijkiae : Caracterization of the polyketide synthases involved in biosynthesis of ochratoxin A, penicillic acid, asperlactone and isoasperlactone in aspergillus westerdijkiae (a molecular approach). (Doctoral Dissertation). INP Toulouse. Retrieved from http://www.theses.fr/2009INPT004A

Chicago Manual of Style (16th Edition):

Bacha, Nafees. “Caractérisation des polycétones synthases intervenant dans la biosynthèse d’ochratoxine A, d’acide pénicillique, d’asperlactone et d’isoasperlactone chez aspergillus westerdijkiae : Caracterization of the polyketide synthases involved in biosynthesis of ochratoxin A, penicillic acid, asperlactone and isoasperlactone in aspergillus westerdijkiae (a molecular approach).” 2009. Doctoral Dissertation, INP Toulouse. Accessed January 16, 2021. http://www.theses.fr/2009INPT004A.

MLA Handbook (7th Edition):

Bacha, Nafees. “Caractérisation des polycétones synthases intervenant dans la biosynthèse d’ochratoxine A, d’acide pénicillique, d’asperlactone et d’isoasperlactone chez aspergillus westerdijkiae : Caracterization of the polyketide synthases involved in biosynthesis of ochratoxin A, penicillic acid, asperlactone and isoasperlactone in aspergillus westerdijkiae (a molecular approach).” 2009. Web. 16 Jan 2021.

Vancouver:

Bacha N. Caractérisation des polycétones synthases intervenant dans la biosynthèse d’ochratoxine A, d’acide pénicillique, d’asperlactone et d’isoasperlactone chez aspergillus westerdijkiae : Caracterization of the polyketide synthases involved in biosynthesis of ochratoxin A, penicillic acid, asperlactone and isoasperlactone in aspergillus westerdijkiae (a molecular approach). [Internet] [Doctoral dissertation]. INP Toulouse; 2009. [cited 2021 Jan 16]. Available from: http://www.theses.fr/2009INPT004A.

Council of Science Editors:

Bacha N. Caractérisation des polycétones synthases intervenant dans la biosynthèse d’ochratoxine A, d’acide pénicillique, d’asperlactone et d’isoasperlactone chez aspergillus westerdijkiae : Caracterization of the polyketide synthases involved in biosynthesis of ochratoxin A, penicillic acid, asperlactone and isoasperlactone in aspergillus westerdijkiae (a molecular approach). [Doctoral Dissertation]. INP Toulouse; 2009. Available from: http://www.theses.fr/2009INPT004A

3. Δούκας, Ελευθέριος. Βιοχημική και μοριακή διερεύνηση της επίδρασης των μεταλλαγών ανθεκτικότητας στα τριαζολικά μυκητοκτόνα στην παραγωγή μυκοτοξινών από μύκητες του γένους aspergillus.

Degree: 2009, Agricultural University of Athens; Γεωπονικό Πανεπιστήμιο Αθηνών

Mutants of the mycotoxigenic fungi Aspergillus parasiticus Speare and Aspergillus westerdijkiae Frisvad and Samson, moderately resistant to azole fungicides were isolated after UV-mutagenesis and selection on media containing flusilazole and epoxiconazole respectively. Studies on the effect of mutation(s) on the mycotoxin production resulted in the identification of two resistant phenotypes: mycotoxigenic, (afl+ in A. parasiticus and och+ in A. westerdijkiae) and non-mycotoxigenic (afl- in A. parasiticus and och- in A. westerdijkiae) mutant strains. All aflatoxigenic mutant isolates of A. parasiticus studied, produced on artificial medium aflatoxins at higher concentrations (115.4 - 189.7 % in total aflatoxin production) compared to the wild-type parent strain. A further increase in aflatoxin production was observed in ZG8 resistant strain when grown on flusilazole-amended medium (95.3 %). High aflatoxin concentrations (426.5% increase in total aflatoxin production) compared to the wild-type were also found in ZG11 mutant strain, after inoculation on wheat grains. In the case of A. westerdijkiae mutant strains, a negative correlation between fungicide resistance and ochratoxin production was found, both on artificial medium and on wheat grains. Study of fitness parameters in A. parasiticus mutant isolates, showed that resistance mutation(s) negatively affected the phenotypic fitness characteristics, such as the radial growth, the conidiation and mycelia production in the non aflatoxigenic isolates (afl-). The values of the above fitness parameters were significantly lower in all the non aflatoxigenic (afl-) mutants compared to the aflatoxigenic (afl+) and the wild-type parent strain. On the other hand, the fungicide resistance mutation(s) in A. westerdijkiae were found to affect or not to affect these ecological fitness parameters. Cross-resistance studies with other fungicides, showed that azole resistance mutation(s) caused a reduction in sensitivity of all A. parasiticus mutant strains, also to the triazole tebuconazole and the imidazole imazalil from the DMI group. Moreover, a multi-drug resistance of the A. parasiticus non-aflatoxigenic isolates (afl-) to chemically unrelated fungicides, as the benzimidazole benomyl, the anilinopyrimidine cyprodinil, the phenylpyridinamine fluazinam and the fungicides from the aromatic hydrocarbons and dicarboxamide group (AHDs) iprodione and tolclofos-methyl, was observed. In the case of A. westerdijkiae, all mutant strains studied exhibited reduced sensitivity to the DMIs flusilazole, difenoconazole and imazalil, while in the majority of them a reduction in sensitivity to other chemically unrelated site specific inhibitors as fenpropimorph (morpholine), fludioxonil, iprodione, cyprodinil, fluazinam, boscalid (carboxamide) and pyraclostrobil (Qo inhibitor) was also found. No effect in the sensitivity to the benzimidazole carbendazim and a negative cross-resistance relationship with the non-specific inhibitor chlorothalonil were observed in all mutant strains of A.…

Subjects/Keywords: Ασπέργιλλοι; Ανθεκτικότητα; Μυκητοκτόνα; Τριαζόλες; Μυκοτοξίνες; Βιοχημικός έλεγχος; Aspergillus sp; Aspergillus parasiticus; Aspergillus westerdijkiae; Fungicide resistance; Triazoles; Mycotoxins; Biochemical control

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Δούκας, . . (2009). Βιοχημική και μοριακή διερεύνηση της επίδρασης των μεταλλαγών ανθεκτικότητας στα τριαζολικά μυκητοκτόνα στην παραγωγή μυκοτοξινών από μύκητες του γένους aspergillus. (Thesis). Agricultural University of Athens; Γεωπονικό Πανεπιστήμιο Αθηνών. Retrieved from http://hdl.handle.net/10442/hedi/19879

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Δούκας, Ελευθέριος. “Βιοχημική και μοριακή διερεύνηση της επίδρασης των μεταλλαγών ανθεκτικότητας στα τριαζολικά μυκητοκτόνα στην παραγωγή μυκοτοξινών από μύκητες του γένους aspergillus.” 2009. Thesis, Agricultural University of Athens; Γεωπονικό Πανεπιστήμιο Αθηνών. Accessed January 16, 2021. http://hdl.handle.net/10442/hedi/19879.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Δούκας, Ελευθέριος. “Βιοχημική και μοριακή διερεύνηση της επίδρασης των μεταλλαγών ανθεκτικότητας στα τριαζολικά μυκητοκτόνα στην παραγωγή μυκοτοξινών από μύκητες του γένους aspergillus.” 2009. Web. 16 Jan 2021.

Vancouver:

Δούκας . Βιοχημική και μοριακή διερεύνηση της επίδρασης των μεταλλαγών ανθεκτικότητας στα τριαζολικά μυκητοκτόνα στην παραγωγή μυκοτοξινών από μύκητες του γένους aspergillus. [Internet] [Thesis]. Agricultural University of Athens; Γεωπονικό Πανεπιστήμιο Αθηνών; 2009. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/10442/hedi/19879.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Δούκας . Βιοχημική και μοριακή διερεύνηση της επίδρασης των μεταλλαγών ανθεκτικότητας στα τριαζολικά μυκητοκτόνα στην παραγωγή μυκοτοξινών από μύκητες του γένους aspergillus. [Thesis]. Agricultural University of Athens; Γεωπονικό Πανεπιστήμιο Αθηνών; 2009. Available from: http://hdl.handle.net/10442/hedi/19879

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

.