ABSTRACT
Species of the Aspergillus niger aggregate are known to produce feruloyl esterases, enzymes involved in the degradation of cell wall polymers. However, species delineation is difficult in these fungi. We combined AFLP analysis with ITS rDNA and beta-tubulin sequencing to characterize the isolates of this aggregate in terms of feruloyl esterase production. A preliminary re-examination of isolates based on comparison of ITS rDNA and beta-tubulin sequences with those of typical taxa deposited in international collections led us to re-identify the isolates as members of the species A. niger, A. foetidus and A. tubingensis. Molecular clustering based on beta-tubulin data and AFLP analysis showed that the strains of A. niger formed a homogenous phylogenetic group distinguished by either zero or type A feruloyl esterase activity, while strains A. foetidus and A. tubingensis exhibited type B feruloyl esterase activity when grown on sugar beet pulp.
Subject(s)
Aspergillus niger/enzymology , Carboxylic Ester Hydrolases/metabolism , Fungal Proteins/metabolism , Phylogeny , Aspergillus niger/classification , Aspergillus niger/genetics , DNA, Fungal/chemistry , DNA, Fungal/genetics , DNA, Ribosomal Spacer/genetics , Molecular Sequence Data , Polymorphism, Restriction Fragment Length , Sequence Analysis, DNA , Tubulin/geneticsABSTRACT
To 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 microg/L) and confirmed the major implication of A. carbonarius in ochratoxin A contamination.
Subject(s)
Aspergillus/isolation & purification , Fruit/microbiology , Ochratoxins/biosynthesis , Vitis/microbiology , Wine , Aspergillus/metabolism , Aspergillus niger/isolation & purification , Aspergillus niger/metabolism , Food Contamination , France , Fruit/chemistry , Ochratoxins/analysis , Vitis/chemistryABSTRACT
This 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.
Subject(s)
Cyclodextrins , Fluorenes/metabolism , Fungi/metabolism , Hazardous Substances/metabolism , Soil Pollutants/metabolism , Absidia/isolation & purification , Absidia/metabolism , Biodegradation, Environmental , Fungi/isolation & purification , Kinetics , Soil MicrobiologyABSTRACT
Eleven samples of grapes and musts used in red table wines were investigated for the occurrence of potential ochratoxin A (OTA)-producing molds. From these samples, 59 filamentous fungi and 2 yeasts were isolated. Among the 30 genera isolated, Deuteromycetes were the most frequent (70%) followed by Ascomycetes (10%). Six of the eleven grapes samples were contaminated by potentially ochratoxinogenic strains (Penicillium chrysogenum and Aspergillus carbonarius). When cultivated in vitro on solid complex media, the 14 strains of A. carbonarius produced OTA. No other species produced OTA under the same conditions. Among must samples, eight of eleven were found to be contaminated by OTA (concentrations from <10 to 461 ng/L). There is a strong correlation between the presence of ochratoxin-producing strains on grapes and OTA in musts. These findings should be connected with the OTA contamination of human blood in these areas and in France.
