Fungal microflora and ochratoxin a risk in French vineyards

International audienceTo evaluate the ochratoxin A risk in French vineyards, five winemaking regions were investigated. An exhaustive survey of the fungal microflora of 60 grape samples was carried out at two development stages of the berries: end of veraison and harvest time. Potentially toxinogenic fungi isolated from grapes were assessed in vitro for ochratoxin A production. Ochratoxin A was also quantified in musts by high-performance liquid chromatography after cleanup on immunoaffinity columns. Among the 90 species identified, almost half are listed as mycotoxin producers, but only 2 are potentially ochratoxinogenic: Aspergillus carbonarius and Aspergillus niger. Among these strains, only A. carbonarius, isolated from the Languedoc region at harvest time, was found to produce ochratoxin A. These results were in accordance with the presence of ochratoxin A in French southern region musts (0.01-0.43 mug/L) and confirmed the major implication of A. carbonarius in ochratoxin A contamination

Effects of fungal bioaugmentation and cyclodextrin amendment on fluorene degradation in soil slurry

International audienceThis study assesses the potential of fungal bioaugmentation and the effect of maltosyl- cyclodextrin amendment, as an approach to accelerate fluorene biodegradation in soil slurries. 47 fungal strains isolated from a contaminated site were tested in the biodegradation of fluorene. Results showed the greater efficiency of " adaptated" fungi isolated from contaminated soil vs. reference strains belonging to the collection of the laboratory. These assays allowed us to select the most efficient strain, Absidia cylindrospora, which was used in a bioaugmentation process. In the presence of Absidia cylindrospora, more than 90% of the fluorene was removed in 288 h while 576 h were necessary in the absence of fungal bioaugmentation. Maltosyl- cyclodextrin, a branched- cyclodextrin was chosen in order to optimize fluorene bioavailability and biodegradation in soil slurries. The results of this study indicate that Absidia cylindrospora and maltosyl- cyclodextrin could be used successfully in bioremediation systems

Enhanced degradation of fluorene in soil slurry by Absidia cylindrospora and maltosyl-cyclodextrin

International audienceThis study investigates the fungal biodegradation of fluorene, a polycyclic aromatic hydrocarbon, in liquid medium and soil slurry. Fungal strains and cyclodextrins were used in order to degrade fluorene and optimize fluorene bioavailability and degradation in soil slurries. After a procedure of selection in solid and liquid media, maltosyl-cyclodextrin, a branched cyclodextrin was chosen. 47 fungal strains isolated from a contaminated site were tested for biodegradation. Results showed the greater efficiency of "adapted" fungi isolated from contaminated soil vs reference strains belonging to the collection of the laboratory. These assays allowed us to select the most efficient strain, Absidia cylindrospora, which was used in a bioaugmentation process. Bioaugmentation tests were performed in an artificially contaminated non-sterile soil. In the presence of A. cylindrospora, more than 90% of the fluorene was degraded within 288 h, while 576 h were necessary in the absence of fungal bioremediation. It also appeared that biodegradation was enhanced by amendment with previously selected maltosyl-cyclodextrin. The results of this study indicate that A. cylindrospora and maltosyl-cyclodextrin could be used successfully in fluorene bioremediation systems. (C) 2004 Elsevier Ltd. All rights reserved

Investigations on cultural and cellulolytic activity in Pyricularia oryzae Cavara

The growth of Pyricularia oryzae Cavara was studied on 2 solid complex media, malt and rice extracts, under different conditions. The 2 culture media encouraged growth of the phytopathogen but their effects varied between strains. Statistical analysis showed that the effect of media on the growth of the different strains was non-significant, while inter-strain differences were due to pH. Growth was better at pH 6 and 7 than at pH 5, and was inhibited below 5 and above 37°C. It was optimum at 28°C, moderate at 23°C and minimum at 15°C, with very low sporulation or without sporulation, depending on strains. Low relative humidity apparently lowered sporulation in all strains. On synthetic media, nitrate-N as growth nutrient was preferred to ammonium-N by P oryzae. A remarkably better development was observed in synthetic medium containing sodium nitrate in place of ammonium salts. Four strains out of 5 were tested for cellulolytic activity. The levels of cellulose degradation were not consistent in Avicel azure and Cellulose azure for all the strains, and showed various degrees of positive activity.Conditions de culture et activité cellulolytique chez Pyricularia oryzae Cavara. La croissance de Pyricularia oryzae Cavara a été étudiée sur 2 milieux solides complexes à base d'extraits de malt et de riz, sous différentes conditions. Ces 2 milieux favorisent le développement du pathogène d'une manière variable selon les souches. L'analyse statistique montre que l'effet du milieu sur la croissance n'est pas significatif alors que les différences entre souches sont dues au pH. La croissance est meilleure à pH 6 et 7 qu'à pH 5 et est inhibée en dessous de 5°C et au-dessus de 37°C. Elle est optimale à 28 °C, modérée à 23°C et minimale à 15°C avec une sporulation faible ou nulle selon les souches. Sur milieu synthétique P oryzae préfère l'azote nitrique à l'azote ammoniacal. Le développement est significativement meilleur lorsque le nitrate de sodium remplace les sels d'ammonium. La recherche de l'activité cellulolytique de 4 souches a montré différents niveaux d'activité sur Avicel azure et Cellulose azure

Etude de la toxicité des composés phénoliques modèles de la lignine vis-à-vis de 1040 souches de champignons

La toxicité de 7 composés phénoliques modèles de la lignine vis-à-vis de 1040 champignons est étudiée. La plupart des souches ont une bonne tolérance à ces composés.. Les acides protocatéchique, syringique et vanillique sont les moins toxiques, alors que le phénol et le catéchol sont les plus toxiques . L'acide férulique et le gaïacol sont moyennement toxiques. Certains groupes taxonomiq1,les comme les Zygomycètes sont très résistants à la toxicité de ces phénols; tandis que d'autres tels que les Agonomycètes le sont moins. Les champignons déporvus d'activité phénoloxydasique tolèrent mieux la présence du catéchol et du phénol. Quant aux autres phénols, leur toxicité ne semble pas être modifiée par la présence ou non de ces enzymes. L'addition d'un carboxyle sur le noyau aromatique du catéchol et du gaïacol diminue nettement la toxicité de ces 2 composés; alors que l'addition d'un hydroxyle au phénol ou d'un groupement éthylènique à l'acide vailillique l'augmente sensiblement

Micromycètes et biorémédiation des eaux polluées et des sols contaminés par les pesticides

The GEDEXE team having a collection of more than 1360 strains of micromycetes belonging to different taxonomic group, attaches a particular attention to the development and selection of efficient strains capable of degrading several active matters commonly used in agriculture. Experiments were performed in liquid synthetic medium at room temperature and under continuous agitation. The disappearance of the parent molecule was monitored by HPLC. The various molecules studied are: the pentachlorophenol (PCP), the pentachloronitrobenzene (PCNB) and the atrazine herbicide (ATZ). Strains of Zygomycetes and in particular the genera Cunninghamella, Rhizopus and Mucor appeared to be suitable and efficient regarding the disappearance of these three molecules and to enough high percentages exceeding in some cases the threshold of 50%. These results vary not only within the even taxonomic groups and the same genus but also according to the molecule tested. In sum, Atrazine seems to be more recalcitrant among its equivalents of pesticides. / L'équipe du GEDEXE dispose d'une mycothèque de plus de 1160 souches de micromycètes appartenant aux différents groupes taxonomiques. Elle porte une attention particulière à la recherche de souches performantes aptes à dégrader des matières actives couramment utilisées en agriculture. Les expériences sont conduites en milieu liquide synthétique à température ambiante et sous agitation continue. La disparition de la molécule mère est appréciée par CLHP. Les diverses molécules déjà étudiées sont : le pentachlorophénol (PCP) le pentachloronitrobenzène (PCNB) et l'atrazine (ATZ). Des souches de zygomycètes sont apparues efficaces quant à la disparition de plusieurs de ces molécules et à des pourcentages assez élevés dépassant dans certains cas le seuil de 50%. En somme, seule l'atrazine semble être plus récalcitrante parmi ses homologues pesticides. Ces résultats varient non seulement au sein du même groupe taxonomique et du même genre mais aussi avec la molécule considérée