Champignons ochratoxinogènes et ochratoxine A (OTA) dans des vignobles Français et procédés biologiques de décontamination de l'OTA dans les moûts de raisin

L'étude de la dynamique des populations fongiques totales et ochratoxinogènes et du contenu en OTA des raisins de vignobles français nous a permis de déterminer en premier lieu l'agent causal responsable de cette contamination. Il s'agit principalement de l'espèce Aspergillus carbonarius suivie du groupe des Aspergillus niger. Le bassin méditerranéen et plus précisément le Languedoc-Roussillon était la région la plus contaminée à l'OTA en France et les raisins récoltés au stade vendange était à leurs maximum de contamination. Le stress occasionné chez certains champignons ochratoxinogènes par l'emploi de certains agents fongicides ou antimicrobiens pourrait être stimulateur de leur pouvoir ochratoxinogène. Ceci rend encore plus difficile la gestion sanitaire et la prévision de la contamination au sein du vignoble. Dans le cadre de la gestion curative de l'OTA, les levures mortes traitées à la chaleur (Saccharomyces serivisiae et Saccharomyces bayanus) avaient un pouvoir rapide et intéressant à adsorber l'OTA et seraient d'un grand intérêt pour l'élimination de la toxine. Les Aspergillus de la section Nigri avaient montré à la fois un potentiel d'adsorption et de dégradation de la toxine. L'efficacité d'A. niger et d'A. japonicus à éliminer l'OTA, leur faible impact sur la qualité des jus contaminés, le label GRAS accordé au premier et l'ochratoxigénicité rarement évoquée pour le deuxième, font de ces deux espèces un espoir dans la décontamination au sein de la filière. ABSTRACT : During a survey conducted in France over three years in 10 vineyards from four winemaking regions with different geographical locations and climatic conditions, the ochratoxigenic potential of fungal isolates and their occurrence on grapes were studied. A. carbonarius was found the main OTA producer on French grapes and harvest time was the most critical period influencing OTA contamination. Grapes from Languedoc-Roussillon region were most infested with ochratoxigenic fungi and had the highest concentrations of OTA. Some fungicides and antimicrobials used in vineyards could stress fungi and stimulate their OTA production. This may be added to the various and complex factors determining OTA contamination in grapes and complicate prevention in vineyards. To manage this contamination, different microorganisms belonging to grape microbiota or with winemaking interest were tested for their capacity to remove OTA. Heat treated yeasts (Saccharomyces serivisiae and Saccharomyces bayanus) showed an interesting potential to adsorb rapidly and totally OTA from grape juices. The black aspergilli species had both adsorption and degradation potentials. A. niger and A. japonicus were the most interesting in removing OTA and could be a new hope for Grape juices and musts decontamination

Identification of mycobiota from Tunisian olives and determination of their mycotoxigenic profile

In the Mediterranean basin, a large number of olive varieties are produced and cultivated. In Tunisia, olive culture represents one of the most significant agricultural products that is produced annually. Storage under inadequate conditions poses serious problems concerning fungal contamination, with consequent defects and potential mycotoxin production in olives and olive oils. In this study, we aimed to identify and characterize a selected group of fungi previously isolated from olives from Tunisian groves. For this purpose, 28 fungi were selected for identification by a polyphasic approach consisting of morphological identification on Malt Extract Agar (MEA) and Czapek Yeast Autolysate (CYA); physiological identification by the Erlich test (for the genus Penicillium only); and molecular identification by sequencing of the ITS region of the rRNA gene. Mycotoxigenic ability of fungi was screened on Coconut Agar Medium (CAM). Methanolic extracts of those fungi showing fluorescence on CAM wereobtained from CYA cultures and analysed by HPLC. From morphological and molecular identification, eight species belonging to the genera Alternaria, Aspergillus, Fusarium, Penicillium, Pleospora and Tricothecium and were identified. Results showed several isolates were able to produce toxins on CAM, by showing green or orange fluorescence. HPLC analysis are being developed.info:eu-repo/semantics/publishedVersio

Ochratoxin A removal in synthetic and natural grape juices by selected oenological Saccharomyces strains

To assess, for the first time the efficiency in removing ochratoxin A (OTA) from laboratory medium [yeast peptone glucose (YPG)], synthetic grape juice medium (SGM) and natural grape juice by viable and dead (heat and acid-treated) oenological Saccharomyces strains (five S. cerevisiae and one S. bayanus) compared with a commercial yeast walls additive. Levels of OTA during its interaction with six oenological Saccharomyces strains (five S. cerevisiae and one S. bayanus) or with a commercial yeast walls additive in YPG medium, in SGM or in natural grape juices was assessed by HPLC after appropriate extraction methods. A significant decrease of OTA levels in YPG medium and SGM was observed for many of the growing strains reaching a maximum of 45%, but no degradation products were detected. With both heat and acid pretreated yeasts, OTA removal was enhanced, indicating that adsorption, not catabolism, is the mechanism to reduce OTA concentrations. Adsorption was also improved when the yeast concentration was increased and when the pH of the medium was lower. Approximately 90% of OTA was bound rapidly within 5 min and up to 72 h of incubation with heat-treated cells of either S. cerevisiae or S. bayanus. A comparative study between heat-treated cells (HC) and commercial yeast walls (YW) (used as oenological additive), introduced at two different concentrations (0.2 and 6.7 g l(-1)) in an OTA-contaminated grape juice, showed the highest efficiency by HC to adsorb rapidly within 5 min the total amount of the mycotoxin. Oenological S. cerevisiae and S. bayanus were able to remove ochatoxin A from synthetic and natural grape juices. This removal was rapid and improved by dead yeasts having more efficiency than commercial yeast walls. The efficiency of heat-treated yeasts to remove OTA gives a new hope for grape juice and must decontamination avoiding negative impacts on human health

Ecophysiology of Penicillium expansum and patulin production in synthetic and olive-based media

Olives and their derivatives, in particular olive oil, represent one of the most significant agricultural products in the Mediterranean basin. Storage under inadequate conditions poses serious problems concerning fungal contamination, with consequent defects and potential mycotoxin production in olives and olive oils. Penicillium expansum represents one of the most significant postharvest pathogens in several fruits, including olives. Not only it causes blue mold but also is one of the most relevant patulin producing species of the genus Penicillium. The aim of this research was to evaluate the ecophysiological conditions governing growth and PAT production by P. expansum strains previously isolated from Tunisian olives. For this purpose, four P. expansum isolates were tested in a synthetic medium (Czapek Yeast Autolysate, CYA) and in olive-based medium (OM) for their ability to grow and produce PAT under different temperatures (4 °C, 15 °C and 25 °C) for 10 and 20 d. The mycotoxin was analysed by HPLC-UV. Results showed that all isolates were able to grow on tested media at different temperatures. Different PAT production profiles were found, showing that at 25 °C P. expansum isolates were able to produce PAT on CYA and OM medium. At 15 °C the production of PAT was only detected on CYA medium, while no PAT production was detected at 4 °C for the two media.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) and FEDER under Programme PT2020 for financial support to CIMO (UID/AGR/00690/2019).info:eu-repo/semantics/publishedVersio

Vietnam in the Regional and Global TNC Value Chain

A survey was conducted in France over three years (2001-2003) in 10 vineyards from four winemaking regions with different geographical locations and climatic conditions. Aspergillus and Penicillium were isolated from the grapes. During 2001 and 2002, from setting to harvest, the total numbers of fungal isolates were respectively 721 and 711 increasing in 2003 to reach 1035. The Aspergillus genus was essentially represented by Nigri section (99%) and was predominant (80% ±4.6) when compared to Penicillium (20% ±4.6). Regardless of sampling year, 32.5% (±σ = 1.26) of the fungal isolates were OTA producers and 93% (±σ = 2.65) belonging to black aspergilli. The ochratoxigenic potential of the isolates and their occurrence on grapes revealed that A. carbonarius was the main OTA producer on French grapes. At harvest time, the fungal population was maximal and this was the most critical period influencing OTA contamination. Grapes from Languedoc-Roussillon region were most infested with ochratoxigenic fungi and had the highest concentrations of OTA. All these results could be of prime importance for further preventive action against ochratoxigenic species in vineyards to limit the contamination of grapes and grape products in France

Fungal flora from Tunisian olives carposphere: diversity and volatile organic compounds

Plant phyllosphere is an enormous environment on Earth densely colonized by microorganisms. Those microbiomes play essential roles in processes related to plant development and pathogen defense. They release different metabolites working as interspecies messages in the environment. Volatile organic compounds are among those released messages. Among the worldwide phyllosphere, oliveyards are widely spread in the Mediterranean basin. Like all foods, olives and oil quality begin in the field. Fungal microbiomes through their interactions with olives trees could have an impact on oil quality. In this work we were interested on fungal microbiomes from olives carposphere. Fifteen Tunisian fields from four climatic regions were studied. Fungi were isolated and identified to species with microscopic and molecular techniques. Their aromatic profiles were analysed by solid-phase micro-extraction (SPME) coupled to gas cromatography and mass spectrometry. Results showed that genus Penicillium (P. polonicum, P. crustosum and P. expansum) was predominant. The major volatiles identified were: Styrene, 1-octen-3-ol, 3-octanol, 3-octanone, 1,8-cineole. Styrene is a volatile hydrocarbon reported as 80 times more toxic than the volatile phase of toluene. The following three are oxylipins. They play essential roles in fungal morphogenesis and pathogenesis and are reported as metabolites with musty and earthy characteristics able to induce mycotoxin production. The last one is a terpene with a eucalyptus herbal camphor odor note. Could those volatiles be found on olives and olive oils? Could they impact chemical and sensory olive oils qualities? Could they induce mycotoxin production in olive oils? All those questions still to be answered…info:eu-repo/semantics/publishedVersio

Conidia of black aspergilli as new biological adsorbents for ochratoxin A in grape juices and musts

Biological removal of ochratoxin A (OTA) by living and heat-treated dead conidia of black Aspergillus isolates representing the species Aspergillus niger, A. carbonarius and A. japonicus in synthetic and natural grape juices was found to be a two-stage phenomenon. Several lines of evidence suggest that the first observed stage was passive, metabolism was not required and OTA adsorption on conidia of black aspergilli could be involved. This removal was fast, without delay just after conidial inoculation both in synthetic and natural grape juices. Moreover, even non-viable, heat-treated conidia were capable of removing OTA. Finally, no OTA degradation products were detected. In the second observed stage, removal of OTA was linked to degradation by live conidia only. Ochratoxin alpha, a degradation product of OTA was detected in the medium after incubation for 30 and 14 hours for biseriate (A. niger and A. carbonarius) and uniseriate (A. japonicus) black aspergilli, respectively when well-developed mycelium appeared. Comparisons between the three black Aspergillus isolates tested showed that A. carbonarius detoxified grape juice most effectively. However, this species often produces OTA. A. niger and A. japonicus isolates were also effective and because those species are not systematically OTA producers, they could be interesting for further OTA detoxification processes in grape juices and musts

Ecophysiology of Penicillium expansum and patulin production in synthetic and olive-based media

The olive and its derivatives, in particular olive oil, represent one of the most significant agricultural products in the Mediterranean basin. Storage under inadequate conditions poses serious problems concerning fungal contamination, with consequent defects and potential mycotoxin production in olives and olive oils. Penicillium expansum represents one of the most significant postharvest pathogens in several fruits, including olives. Not only it causes blue mold but also is one of the most relevant patulin (PAT) producing species of the genus Penicillium. The aim of this research was to evaluate the ecophysiological conditions governing growth and PAT production by P. expansum strains previously isolated from Tunisian olives. For this purpose, four P. expansum isolates were tested in a synthetic medium (Czapek Yeast Autolysate, CYA) and in olive-based medium (OM) for their ability to grow and produce PAT under different temperatures (4 ºC, 15°ºC and 25°ºC) for 10 and 20 days. The mycotoxin was analysed by HPLC-UV. Results showed that all isolates were able to grow on tested media at different temperatures. Different PAT production profiles were found, showing that at 25 ºC P. expansum isolates were able to produce PAT on CYA and OM medium. At 15 ºC the production of PAT was only detected on CYA medium, while no PAT production was detected at 4 ºC for the two media.info:eu-repo/semantics/publishedVersio

Biodegradation of ochratoxin A by Aspergillus section Nigri species isolated from French grapes:a potential means of ochratoxin A decontamination in grape juices and musts

Ochratoxin A (OTA) is a very dangerous mycotoxin, the presence of which is often reported in different foods, as well as in beverages such as grapes, grape juices and wines. Detoxifying these products is therefore of prime importance in protecting consumer health, and biological approaches have been the most promising methods. In this report, 40 isolates representing the black apergilli species Aspergillus carbonarius, A. niger aggregate and A. japonicus, isolated on French grapes, were assessed for OTA degradation capacities in CZAPEK yeast extract broth (CYB) and in a synthetic grape juice medium (SGM) contaminated with OTA at 2 mg L1 (5 mM). It was clearly observed that in both media these fungi had the ability to degrade OTA to OTa (ochratoxina). However, there were differences between the media used and species tested during OTA degradation. In SGM and CYB, 77% and 45% of the isolates, respectively were able to degrade more than 80% of the OTA. Despite a better growth on SGM, specific OTA degradation was higher on CYB for most of the isolates. Kinetic studies carried out on SGM with three black Aspergillus isolates all showed different OTA degradation rates. After 9 days of incubation, OTa had decreased, whereas an unknown compound appeared. A. niger could be the first interesting species for OTA detoxification processes, followed by A. japonicus