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Papers by Florentina Radoï-Matei

Agriculture and Agricultural Science Procedia, 2015

Agriculture and Agricultural Science Procedia, 2015

Recently there is increased interest in the identification and characterization of new valuable y... more Recently there is increased interest in the identification and characterization of new valuable yeast strains to be used for the production of quality wines with specific traits. Such new strains need to be tested extensively regarding their behavior in relation to various factors. The paper presents results on the resistance to ethanol of ten yeast strains from the Saccharomyces genus selected from Romanian vineyards. The behavior of yeasts in the presence of ethanol was investigated using a calorimetric technique which allows for the determination of the growth rate as well as quantitative parameters that describe the inhibition of microbial growth by ethanol, such as the Minimum Inhibitory Concentration (MIC) and the concentration of ethanol that reduces microbial activity by 50%. It can also indicate if the inhibition mechanism is of a bactericidal or of a bacteriostatic nature. The technique allows for a comparison of the various yeast strains from the viewpoint of ethanol tole...

Over the last few decades stochastic study in biology has acquired global dimension. The preventi... more Over the last few decades stochastic study in biology has acquired global dimension. The prevention of the food product contamination with toxinogenic moulds is an actuality problem of microbiology. This means that it is necessary to have precise diagnostic methods in order to predict and describe in detail the dynamic of the alteration. Considering all these facts, we tried to develop in our paper a stochastic model to answer to this question. First, we have established some conclusions regarding the growth model; for this, we have made appropriate graphics corresponding evolution strains of Penicillium crysogenum and Fusarium graminearum during the 14 days. Secondly, we have examined the phenomenon of growth as a non-homogeneous Poisson process involving periodic variations in the occurrence rate and we have obtained the probability density function of the time intervals of growth.

The use of energy crops (maize straw, wheat straw, barley straw etc.) as substratefor renewable e... more The use of energy crops (maize straw, wheat straw, barley straw etc.) as substratefor renewable energy production (e.g. biogas) is more efficient when it is degradedby different hydrolysis methods. However, fibers contained inside energy crops (e.g.cellulose and hemicellulose) are only hardly and slowly degraded by anaerobicbacteria. The slow degradation of these substances can decrease the methane yieldsof agricultural biogas plants.In the present study, we investigated the efficiency ofcombined pretreatment (different concentrations H2SO4 + 30 minutes at 1210C)followed to enzymatic hydrolysis. Testing different concentration of H2SO4, goodresults were obtained for maize whole crop when we used combined pretreatment(3% H2SO4 + 30 minutes at 1210C) followed to enzymatic hydrolysis (3.9 foldhigher) and for Gavott Maize Straw when we used combined pretreatment (2%H2SO4 + 30 minutes at 1210C) followed to enzymatic hydrolysis (3.6 fold higher)comparing with untreated samples.

Predictive microbiology/mycology provides specific tools for microorganisms growth and toxins pro... more Predictive microbiology/mycology provides specific tools for microorganisms growth and toxins productions on the crops, in the ware house and on other levels of the food chain. During a national research scale, from more than 100 toxinogenic moulds isolated from agricultural and food products have been kept for specific studies two high-micotoxins producers strains: Fusarium graminearum MI 113 for deoxinivalenol (DON) and Penicillium crysogenum MI 210 producer of ochratoxin A (OTA). These moulds have been studied for their micotoxins productions on synthetic liquid media under different temperature conditions. The growth rate has been calculated starting from the measurement of radial growth, while de toxin productions have been quantified by immunological semiquantitative tests (Elisa type) and compared with HPLC measurements. The maximum level of DON production has been reached on 26 o C, while for the OTA production has been at 23 o C. A correlation between the growth rate and th...

International Journal of Food Microbiology, 2005

FEMS Yeast Research, 2005

Applied and Environmental Microbiology, 2012

The hybrid nature of lager-brewing yeast strains has been known for 25 years; however, yeast hybr... more The hybrid nature of lager-brewing yeast strains has been known for 25 years; however, yeast hybrids have only recently been described in cider and wine fermentations. In this study, we characterized the hybrid genomes and the relatedness of the Eg8 industrial yeast strain and of 24 Saccharomyces cerevisiae/Saccharomyces kudriavzevii hybrid yeast strains used for wine making in France (Alsace), Germany, Hungary, and the United States. An array-based comparative genome hybridization (aCGH) profile of the Eg8 genome revealed a typical chimeric profile. Measurement of hybrids DNA content per cell by flow cytometry revealed multiple ploidy levels (2n, 3n, or 4n), and restriction fragment length polymorphism analysis of 22 genes indicated variable amounts of S. kudriavzevii genetic content in three representative strains. We developed microsatellite markers for S. kudriavzevii and used them to analyze the diversity of a population isolated from oaks in Ardèche (France). This analysis revealed new insights into the diversity of this species. We then analyzed the diversity of the wine hybrids for 12 S. cerevisiae and 7 S. kudriavzevii microsatellite loci and found that these strains are the products of multiple hybridization events between several S. cerevisiae wine yeast isolates and various S. kudriavzevii strains. The Eg8 lineage appeared remarkable, since it harbors strains found over a wide geographic area, and the interstrain divergence measured with a (δμ)(2) genetic distance indicates an ancient origin. These findings reflect the specific adaptations made by S. cerevisiae/S. kudriavzevii cryophilic hybrids to winery environments in cool climates.

Agriculture and Agricultural Science Procedia, 2015

Agriculture and Agricultural Science Procedia, 2015

Recently there is increased interest in the identification and characterization of new valuable y... more Recently there is increased interest in the identification and characterization of new valuable yeast strains to be used for the production of quality wines with specific traits. Such new strains need to be tested extensively regarding their behavior in relation to various factors. The paper presents results on the resistance to ethanol of ten yeast strains from the Saccharomyces genus selected from Romanian vineyards. The behavior of yeasts in the presence of ethanol was investigated using a calorimetric technique which allows for the determination of the growth rate as well as quantitative parameters that describe the inhibition of microbial growth by ethanol, such as the Minimum Inhibitory Concentration (MIC) and the concentration of ethanol that reduces microbial activity by 50%. It can also indicate if the inhibition mechanism is of a bactericidal or of a bacteriostatic nature. The technique allows for a comparison of the various yeast strains from the viewpoint of ethanol tole...

Over the last few decades stochastic study in biology has acquired global dimension. The preventi... more Over the last few decades stochastic study in biology has acquired global dimension. The prevention of the food product contamination with toxinogenic moulds is an actuality problem of microbiology. This means that it is necessary to have precise diagnostic methods in order to predict and describe in detail the dynamic of the alteration. Considering all these facts, we tried to develop in our paper a stochastic model to answer to this question. First, we have established some conclusions regarding the growth model; for this, we have made appropriate graphics corresponding evolution strains of Penicillium crysogenum and Fusarium graminearum during the 14 days. Secondly, we have examined the phenomenon of growth as a non-homogeneous Poisson process involving periodic variations in the occurrence rate and we have obtained the probability density function of the time intervals of growth.

The use of energy crops (maize straw, wheat straw, barley straw etc.) as substratefor renewable e... more The use of energy crops (maize straw, wheat straw, barley straw etc.) as substratefor renewable energy production (e.g. biogas) is more efficient when it is degradedby different hydrolysis methods. However, fibers contained inside energy crops (e.g.cellulose and hemicellulose) are only hardly and slowly degraded by anaerobicbacteria. The slow degradation of these substances can decrease the methane yieldsof agricultural biogas plants.In the present study, we investigated the efficiency ofcombined pretreatment (different concentrations H2SO4 + 30 minutes at 1210C)followed to enzymatic hydrolysis. Testing different concentration of H2SO4, goodresults were obtained for maize whole crop when we used combined pretreatment(3% H2SO4 + 30 minutes at 1210C) followed to enzymatic hydrolysis (3.9 foldhigher) and for Gavott Maize Straw when we used combined pretreatment (2%H2SO4 + 30 minutes at 1210C) followed to enzymatic hydrolysis (3.6 fold higher)comparing with untreated samples.

Predictive microbiology/mycology provides specific tools for microorganisms growth and toxins pro... more Predictive microbiology/mycology provides specific tools for microorganisms growth and toxins productions on the crops, in the ware house and on other levels of the food chain. During a national research scale, from more than 100 toxinogenic moulds isolated from agricultural and food products have been kept for specific studies two high-micotoxins producers strains: Fusarium graminearum MI 113 for deoxinivalenol (DON) and Penicillium crysogenum MI 210 producer of ochratoxin A (OTA). These moulds have been studied for their micotoxins productions on synthetic liquid media under different temperature conditions. The growth rate has been calculated starting from the measurement of radial growth, while de toxin productions have been quantified by immunological semiquantitative tests (Elisa type) and compared with HPLC measurements. The maximum level of DON production has been reached on 26 o C, while for the OTA production has been at 23 o C. A correlation between the growth rate and th...

International Journal of Food Microbiology, 2005

FEMS Yeast Research, 2005

Applied and Environmental Microbiology, 2012

The hybrid nature of lager-brewing yeast strains has been known for 25 years; however, yeast hybr... more The hybrid nature of lager-brewing yeast strains has been known for 25 years; however, yeast hybrids have only recently been described in cider and wine fermentations. In this study, we characterized the hybrid genomes and the relatedness of the Eg8 industrial yeast strain and of 24 Saccharomyces cerevisiae/Saccharomyces kudriavzevii hybrid yeast strains used for wine making in France (Alsace), Germany, Hungary, and the United States. An array-based comparative genome hybridization (aCGH) profile of the Eg8 genome revealed a typical chimeric profile. Measurement of hybrids DNA content per cell by flow cytometry revealed multiple ploidy levels (2n, 3n, or 4n), and restriction fragment length polymorphism analysis of 22 genes indicated variable amounts of S. kudriavzevii genetic content in three representative strains. We developed microsatellite markers for S. kudriavzevii and used them to analyze the diversity of a population isolated from oaks in Ardèche (France). This analysis revealed new insights into the diversity of this species. We then analyzed the diversity of the wine hybrids for 12 S. cerevisiae and 7 S. kudriavzevii microsatellite loci and found that these strains are the products of multiple hybridization events between several S. cerevisiae wine yeast isolates and various S. kudriavzevii strains. The Eg8 lineage appeared remarkable, since it harbors strains found over a wide geographic area, and the interstrain divergence measured with a (δμ)(2) genetic distance indicates an ancient origin. These findings reflect the specific adaptations made by S. cerevisiae/S. kudriavzevii cryophilic hybrids to winery environments in cool climates.