Non-Saccharomyces wine yeasts are not only proposed to improve the sensory profile of wine but al... more Non-Saccharomyces wine yeasts are not only proposed to improve the sensory profile of wine but also for several distinctive promising features. Among them, biocontrol action at different steps of the wine production chain could be a suitable strategy to reduce the use of sulfur dioxide. In this work, the activity of a selected strain of Metschnikowia pulcherrima was evaluated as inoculum in cold clarification with the aim to reduce SO2 and improve the aromatic profile of the wine. Fermentation processes were carried out at the winery level for two consecutive vintages using a pied de cuve as the starter inoculum coming from indigenous Saccharomyces cerevisiae strains. M. pulcherrima revealed an effective bio-protectant action during the pre-fermentative stage even if the timely and appropriate starter inoculum in the two years permitted the effective control of wild yeasts during the fermentation also in the control trials. In general, the main oenological characters did not show di...
ABSTRACT Different yeast nutrient additions were studied for the 2008 and 2009 vintages of Verdic... more ABSTRACT Different yeast nutrient additions were studied for the 2008 and 2009 vintages of Verdicchio grape juice fermentation. Addition of yeast derivatives at the beginning of fermentation and/or different amounts of diammonium phosphate at various times within the first half of fermentation were examined, with initial yeast assimilable nitrogen concentrations set at 200 and 250 mg l−1. Supplementation with glutathione in combination with this nitrogen addition was also evaluated. Fermentation rates were monitored throughout these fermentations carried out under different nutrient conditions. H2S production during fermentation and synthesis of volatile compounds in the finished wines were quantified; the wines also underwent sensory evaluation. The fermentation kinetics were almost exclusively influenced by the inorganic nitrogen supplementation with diammonium phosphate. H2S evolution was more affected by assimilable nitrogen than glutathione. Diammonium phosphate significantly reduced H2S production, with a further reduction in the presence of yeast derivative. This nitrogen supplementation yielded higher concentrations of acetate esters, and in particular of isoamyl acetate (fruity aromas), which positively influences the analytical and aroma profile of wines and results in a general reduction in 2-phenylethanol production (floral aromas). Overall results (two harvesting times and vintages) indicate that the management with diammonium phosphate and yeast derivative supplementation improves the kinetics of fermentation and provides a good tool to reduce H2S formation and increase the analytical and sensory quality of Verdicchio wine.
Of 105 isolates screened for growth on plates containing olive mill wastewater (OMW), five were s... more Of 105 isolates screened for growth on plates containing olive mill wastewater (OMW), five were selected and identified as Pichia fermentans (Y1, Y4) and Candida sp. (Y2, Y11, and Y18). On the basis of their ability to use phenol at 716 mg l(-1), strains Y2 (15% reduction) and Y4 (18% reduction) were then used to detoxify stored OMW under various operational conditions. Yeast treatment of OMW increased the pH and, in the best conditions (aeration and no glucose addition), the COD decreased (47%) and phytotoxicity was also decreased (56%) probably due to the changes in the composition of phenolic compounds.
This work represents the first attempt to evaluate the precision of the specific oxygen uptake ra... more This work represents the first attempt to evaluate the precision of the specific oxygen uptake rate method expressed in terms of repeatability (r) and reproducibility limits (R). Three laboratories were involved in an inter-laboratory test for the validation of respiration analyses on six biomass samples (three composts and three biostabilized products) having different degrees of biological stability. Both the maximum specific oxygen uptake rate peak (SOUR) and the cumulative oxygen demand after 12 h (OD(12)) and 20 h (OD(20)) of respiration test were investigated. Precisions expressed as the relative standard deviation were in the range of 9-41%. Linear regressions found for r and R, versus OD(12) and OD(20), enabled derivation of precision values (r and R) for all respirometric levels within the operating range. The OD(12) and OD(20) indices were found to be more adequate to indicate biological stability since they were less influenced by random errors than the SOUR index.
The yeast strain Pichia anomala DBVPG 3003 secretes a killer toxin (Pikt) that has antifungal act... more The yeast strain Pichia anomala DBVPG 3003 secretes a killer toxin (Pikt) that has antifungal activity against Brettanomyces/Dekkera sp. yeasts. Pikt interacts with β-1,6-glucan, consistent with binding to the cell wall of sensitive targets. In contrast to that of toxin K1, secreted by Saccharomyces cerevisiae , Pikt killer activity is not mediated by an increase in membrane permeability. Purification of the toxin yielded a homogeneous protein of about 8 kDa, which showed a marked similarity to ubiquitin in terms of molecular mass and N-terminal sequences. Pikt is also specifically recognized by anti-bovine ubiquitin antibodies and, similar to ubiquitin-like peptides, is not absorbed by DEAE-cellulose. However, Pikt differs from ubiquitin in its sensitivity to proteolytic enzymes. Therefore, Pikt appears to be a novel ubiquitin-like peptide that has killer activity.
The use of Kluyveromyces phaffii DBVPG 6076 killer toxin against apiculate wine yeasts has been i... more The use of Kluyveromyces phaffii DBVPG 6076 killer toxin against apiculate wine yeasts has been investigated. The killer toxin of K. phaffii DBVPG 6076 showed extensive anti- Hanseniaspora activity against strains isolated from grape samples. The proteinaceous killer toxin was found to be active in the pH range of 3 to 5 and at temperatures lower than 40°C. These biochemical properties would allow the use of K. phaffii killer toxin in wine making. Fungicidal or fungistatic effects depend on the toxin concentration. Toxin concentrations present in the supernatant during optimal conditions of production (14.3 arbitrary units) exerted a fungicidal effect on a sensitive strain of Hanseniaspora uvarum . At subcritical concentrations (fungistatic effect) the saturation kinetics observed with the increased ratio of killer toxin to H. uvarum cells suggest the presence of a toxin receptor. The inhibitory activity exerted by the killer toxin present in grape juice was comparable to that of su...
Non-Saccharomyces wine yeasts are not only proposed to improve the sensory profile of wine but al... more Non-Saccharomyces wine yeasts are not only proposed to improve the sensory profile of wine but also for several distinctive promising features. Among them, biocontrol action at different steps of the wine production chain could be a suitable strategy to reduce the use of sulfur dioxide. In this work, the activity of a selected strain of Metschnikowia pulcherrima was evaluated as inoculum in cold clarification with the aim to reduce SO2 and improve the aromatic profile of the wine. Fermentation processes were carried out at the winery level for two consecutive vintages using a pied de cuve as the starter inoculum coming from indigenous Saccharomyces cerevisiae strains. M. pulcherrima revealed an effective bio-protectant action during the pre-fermentative stage even if the timely and appropriate starter inoculum in the two years permitted the effective control of wild yeasts during the fermentation also in the control trials. In general, the main oenological characters did not show di...
ABSTRACT Different yeast nutrient additions were studied for the 2008 and 2009 vintages of Verdic... more ABSTRACT Different yeast nutrient additions were studied for the 2008 and 2009 vintages of Verdicchio grape juice fermentation. Addition of yeast derivatives at the beginning of fermentation and/or different amounts of diammonium phosphate at various times within the first half of fermentation were examined, with initial yeast assimilable nitrogen concentrations set at 200 and 250 mg l−1. Supplementation with glutathione in combination with this nitrogen addition was also evaluated. Fermentation rates were monitored throughout these fermentations carried out under different nutrient conditions. H2S production during fermentation and synthesis of volatile compounds in the finished wines were quantified; the wines also underwent sensory evaluation. The fermentation kinetics were almost exclusively influenced by the inorganic nitrogen supplementation with diammonium phosphate. H2S evolution was more affected by assimilable nitrogen than glutathione. Diammonium phosphate significantly reduced H2S production, with a further reduction in the presence of yeast derivative. This nitrogen supplementation yielded higher concentrations of acetate esters, and in particular of isoamyl acetate (fruity aromas), which positively influences the analytical and aroma profile of wines and results in a general reduction in 2-phenylethanol production (floral aromas). Overall results (two harvesting times and vintages) indicate that the management with diammonium phosphate and yeast derivative supplementation improves the kinetics of fermentation and provides a good tool to reduce H2S formation and increase the analytical and sensory quality of Verdicchio wine.
Of 105 isolates screened for growth on plates containing olive mill wastewater (OMW), five were s... more Of 105 isolates screened for growth on plates containing olive mill wastewater (OMW), five were selected and identified as Pichia fermentans (Y1, Y4) and Candida sp. (Y2, Y11, and Y18). On the basis of their ability to use phenol at 716 mg l(-1), strains Y2 (15% reduction) and Y4 (18% reduction) were then used to detoxify stored OMW under various operational conditions. Yeast treatment of OMW increased the pH and, in the best conditions (aeration and no glucose addition), the COD decreased (47%) and phytotoxicity was also decreased (56%) probably due to the changes in the composition of phenolic compounds.
This work represents the first attempt to evaluate the precision of the specific oxygen uptake ra... more This work represents the first attempt to evaluate the precision of the specific oxygen uptake rate method expressed in terms of repeatability (r) and reproducibility limits (R). Three laboratories were involved in an inter-laboratory test for the validation of respiration analyses on six biomass samples (three composts and three biostabilized products) having different degrees of biological stability. Both the maximum specific oxygen uptake rate peak (SOUR) and the cumulative oxygen demand after 12 h (OD(12)) and 20 h (OD(20)) of respiration test were investigated. Precisions expressed as the relative standard deviation were in the range of 9-41%. Linear regressions found for r and R, versus OD(12) and OD(20), enabled derivation of precision values (r and R) for all respirometric levels within the operating range. The OD(12) and OD(20) indices were found to be more adequate to indicate biological stability since they were less influenced by random errors than the SOUR index.
The yeast strain Pichia anomala DBVPG 3003 secretes a killer toxin (Pikt) that has antifungal act... more The yeast strain Pichia anomala DBVPG 3003 secretes a killer toxin (Pikt) that has antifungal activity against Brettanomyces/Dekkera sp. yeasts. Pikt interacts with β-1,6-glucan, consistent with binding to the cell wall of sensitive targets. In contrast to that of toxin K1, secreted by Saccharomyces cerevisiae , Pikt killer activity is not mediated by an increase in membrane permeability. Purification of the toxin yielded a homogeneous protein of about 8 kDa, which showed a marked similarity to ubiquitin in terms of molecular mass and N-terminal sequences. Pikt is also specifically recognized by anti-bovine ubiquitin antibodies and, similar to ubiquitin-like peptides, is not absorbed by DEAE-cellulose. However, Pikt differs from ubiquitin in its sensitivity to proteolytic enzymes. Therefore, Pikt appears to be a novel ubiquitin-like peptide that has killer activity.
The use of Kluyveromyces phaffii DBVPG 6076 killer toxin against apiculate wine yeasts has been i... more The use of Kluyveromyces phaffii DBVPG 6076 killer toxin against apiculate wine yeasts has been investigated. The killer toxin of K. phaffii DBVPG 6076 showed extensive anti- Hanseniaspora activity against strains isolated from grape samples. The proteinaceous killer toxin was found to be active in the pH range of 3 to 5 and at temperatures lower than 40°C. These biochemical properties would allow the use of K. phaffii killer toxin in wine making. Fungicidal or fungistatic effects depend on the toxin concentration. Toxin concentrations present in the supernatant during optimal conditions of production (14.3 arbitrary units) exerted a fungicidal effect on a sensitive strain of Hanseniaspora uvarum . At subcritical concentrations (fungistatic effect) the saturation kinetics observed with the increased ratio of killer toxin to H. uvarum cells suggest the presence of a toxin receptor. The inhibitory activity exerted by the killer toxin present in grape juice was comparable to that of su...
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Papers by Maurizio Ciani