Isolation and characterization of yeast strains with ability to decrease volatile acidity of wines

The level of acetic acid, the main component of volatile acidity, is critical for wine quality. Its concentration in wines is approximately 0.5 g/L and, legally, must remain below 1.0g/L. Winemakers use a procedure called “remostagem” to lower acetic acid of wines with high volatile acidity (above 0.8g/L). The spoiled wine is mixed with freshly crushed grapes (1) in a proportion of no more than 20-30% (v/v). The volatile acidity of this mixture and of the newly made wine should not exceed 0.6 and 0.3 g/L, respectively. The aim of this study is to select wine yeasts capable of decreasing the volatile acidity of spoiled wines. First, from 135 isolates colleted during a “remostagem” procedure, 4 wild yeasts were selected based on their ability to consume acetic acid in the presence of glucose at pH 4,0 or 6,0. The 4 strains were further analyzed regarding simultaneous acetic acid and glucose consumption, specific growth rate and ethanol production in comparison to the commercial strain Lalvin QA23, Saccharomyces cerevisiae IGC 4072 and Zygosaccharomyces bailii ISA 1307, using minimal media containing acetic acid (0.5%, v/v) and glucose (0.5%, w/v) at 25ºC and pH 3,0. Although less efficiently than Z. bailii the 4 isolated strains were able to use acetic acid in the presence of glucose. Their potential application in the deacidification of acidic wines is being studied.Programa Operacional Ciência e Inovação (POCI) 2010 - (FEDER/FCT, POCTI/AGR/56102/2004)

Isolation of yeast strains with ability to reduce volatile acidity of wines

The objective of the present study was to isolate and characterize wine yeasts able to reduce volatile acidity of wines. From a set of 135 yeast isolated during a refermentation wine procedure, four strains revealed ability to use glucose and acetic acid simultaneously. The strains were tested regarding their growth patterns in a differential medium containing glucose (0.2% w/v) and acetic acid (0.5% v/v), at pH 4.0 or 6.0. The selected strains displayed growth associated to color change of the pH indicator of the medium indicative of simultaneous glucose and acetic acid consumption. Three of them were identified as Saccharomyces cerevisiae and one as Lachancea thermotolerans by sequencing the D1/D2 domain of the large subunit (26S) ribosomal DNA. In two culture media containing acidic wines with high glucose/low ethanol or low glucose/high ethanol concentrations, the S. cerevisiae strains showed an initial simultaneous consumption pattern of glucose and acetic acid under both aerobic and limited aerobic conditions, independently of the relative amounts of glucose and ethanol. This results show a high physiological diversity among strains of this species, validating our approach to search for interesting strains among indigenous yeasts. Comparatively, the isolated L. thermotolerans 44C and Zygosaccharomyces bailii ISA1307 were able to exhaust acetic acid only when grown under aerobic conditions. The S. cerevisiae strains characterized in the present study appear promising for the decrease of volatile acidity in acidic wines under the low-oxygen conditions of a typical refermentation process.Fundação para a Ciência e a Tecnologia (FCT) - programme POCI 2010 (project POCI/AGR/56102/2004)

Isolation of yeast strains with ability to reduce volatile acidity of wines

The objective of the present study was to isolate and characterize wine yeasts able to reduce volatile acidity of wines. From a set of 135 yeast isolated during a refermentation wine procedure, four strains revealed ability to use glucose and acetic acid simultaneously. The strains were tested regarding their growth patterns in a differential medium containing glucose (0.2% w/v) and acetic acid (0.5% v/v), at pH 4.0 or 6.0. The selected strains displayed growth associated to color change of the pH indicator of the medium indicative of simultaneous glucose and acetic acid consumption. Three of them were identified as Saccharomyces cerevisiae and one as Lachancea thermotolerans by sequencing the D1/D2 domain of the large subunit (26S) ribosomal DNA. In two culture media containing acidic wines with high glucose/low ethanol or low glucose/high ethanol concentrations, the S. cerevisiae strains showed an initial simultaneous consumption pattern of glucose and acetic acid under both aerobic and limited aerobic conditions, independently of the relative amounts of glucose and ethanol. This results show a high physiological diversity among strains of this species, validating our approach to search for interesting strains among indigenous yeasts. Comparatively, the isolated L. thermotolerans 44C and Zygosaccharomyces bailii ISA1307 were able to exhaust acetic acid only when grown under aerobic conditions. The S. cerevisiae strains characterized in the present study appear promising for the decrease of volatile acidity in acidic wines under the low-oxygen conditions of a typical refermentation process.This study was supported by the programme POCI 2010 (project POCI/AGR/56102/2004

The effect of micro-oxygenation and cell immobilization on the reduction of excessive volatile acidity from wines

In our former studies we isolated and characterized wine yeasts with the ability to reduce volatile acidity of wines during a refermentation process, hich consists in mixing the acidic wine with freshly crushed grapes or musts or, alternatively, in incubating with the residual marc. Herein, we aimed to evaluate the effect of micro-oxygenation on the ability of previously selected S. cerevisiae strains to decrease volatile acidity from spoiled wines, and on possible changes in the wine aroma during such a refermentation processes. Both refermentation processes were carried out at a pilot scale (30 l), with an acidic wine with 2.80 gl−1 acetic acid and applying micro-oxygenation (20 mg.l- 1.h-1 of O2). Our data show that oxygen availability is not a key parameter for glucose and acetic acid consumption, but increased the final biomass for both commercial yeast strains tested. Volatile acidity of the final wines decreased to 0.38 gl-1 up to 0.68 gl-1, depending on the strain used. Combining analytical data (SPME coupled to GC-MS) with the sensorial analysis performed by a trained panel of 5 judges, the wines treated with micro-oxygenation revealed a vegetable character and mouth hardness in comparison to the more floral notes that predominated in wines obtained without micro-oxygenation. Currently, the efficiency of volatile acidity removal by S. cerevisiae S26 entrapped cells in one layer alginate beads or in double layer alginate – chitosan beads is being evaluated. The results indicate that removal is dependent on the initial cell concentration in the beads which showed to be important for bead stability and prevention of cell leakage

Effects of acetic acid, ethanol and SO2 on the removal of volatile acidity from acidic wines by two Saccharomyces cerevisiae commercial strains

Herein we report the influence of different combinations of initial concentration of acetic acid and ethanol on the removal of acetic acid from acidic wines by two commercial Saccharomyces cerevisiae strains S26 and S29. Both strains reduced the volatile acidity of an acidic wine (1.0 g l-1 acetic acid and 11% (v/v) ethanol) by 78% and 48%, respectively. Acetic acid removal by both strains was associated with a decrease in ethanol concentration of about 0.7 – 1.2% (v/v). Strain S26 revealed better removal efficiency due to its higher tolerance to stress factors imposed by acidic wines. We also demonstrate that the strong anti-oxidant and antiseptic effect of sulphur dioxide (SO2) concentrations up to 170 mg l-1 inhibit the ability of both strains to reduce the volatile acidity of an acidic wine under our experimental conditions. Therefore, deacidification should be carried out either in wines stabilized by filtration or in wines with SO2 concentrations below 75 mg l-1. Deacidification of wines with the better performing strain S26 was associated with changes in the concentration of volatile compounds. The most pronounced increase was observed for isoamyl acetate (banana) and ethyl hexanoate (apple, pineapple), with an 18- and 25-fold increment, respectively, to values above the detection threshold. The acetaldehyde concentration of the deacidified wine was 2.3 times higher, and may have a detrimental effect on the wine aroma. In addition, deacidification led to increased fatty acids concentration, but still within the range of values described for spontaneous fermentations, and with apparently no negative impact on the organoleptical properties. We propose the use of S. cerevisiae strain S26 for the efficient reduction of the volatile acidity from acidic wines with acetic acid and ethanol concentrations not higher than 1.0 g l-1 and 11% (v/v), respectively.Fundação para a Ciência e Tecnologi

Reduction of volatile acidity of wines by isolated and commercial yeast strains

The main goal of this study was to isolate and characterize wine yeasts with ability to reduce volatile acidity of wines, using a refermentation process. This enological practice consists in mixing the acidic wine with freshly crushed grapes or musts in a proportion of no more than 20-30% (v/v) or, alternatively, in the incubation of the acidic wine with the residual marc from a finished wine fermentation. From a set of 135 yeast isolates, four strains revealed ability to use glucose and acetic acid simultaneously. Three of them were identified as Saccharomyces cerevisiae and one as Lachancea thermotolerans by sequencing the D1/D2 domain of the 26S ribosomal DNA large subunit. Microsatellite analysis shows, that S. cerevisiae strains 30C and 45C are genetically very similar. With the purpose to further evaluate whether the ability to degrade acetic acid in the presence of glucose was a characteristic of the isolated strains, nine commercial S. cerevisiae strains were chosen for further analysis. From this group, the strains S26, S29 and S30 display a most similar glucose and acetic acid initial simultaneous consumption pattern and therefore were assessed in simulated refermentation assays. In a medium containing an acidic wine with high glucose/low ethanol initial concentrations, under low oxygen availability, the S. cerevisiae strain S29 is the most efficient one. Comparatively, in the same medium, L. thermotolerans 44C is able to decrease significantly acetic acid similarly to the control strain Zygosaccharomyces bailii, but only under aerobic conditions. On the other hand, in a medium containing an acidic wine and low glucose/high ethanol initial concentrations, under aerobic conditions, the S. cerevisiae strain S26 is the most efficient acid degrading strain. Notably, with the same medium, but under limited-aerobic conditions, all the S. cerevisiae strains studied display acetic acid degradation efficiencies identical to Z. bailii ISA 1307. Moreover, S. cerevisiae strains S26 and S29 also reveal capacity to decrease volatile acidity of wines with an elevated content of acetic acid under limited aerobic conditions, and even without the addition of a sugar source. In summary, the S. cerevisiae strains characterized in this work appear promising for oenological applications since they are able to decrease volatile acidity of acidic wines under the low-oxygen conditions of typical refermentation processes.Financially supported by the program POCI 2010 (FEDER/FCT, POCTI/AGR/56102/2004)

The impact of acetate metabolism on yeast fermentative performance and wine quality: reduction of volatile acidity of grape musts and wines

Acetic acid is the main component of the volatile acidity of grape musts and wines. It can be formed as a byproduct of alcoholic fermentation or as a product of the metabolism of acetic and lactic acid bacteria, which can metabolize residual sugars to increase volatile acidity. Acetic acid has a negative impact on yeast fermentative performance and affects the quality of certain types of wine when present above a given concentration. In this minireview, we present an overview of fermentation conditions and grape-must composition favoring acetic acid formation, as well the metabolic pathways leading to its formation and degradation by yeast. The negative effect of acetic acid on the fermentative performance of Saccharomyces cerevisiae will also be covered, including its role as a physiological inducer of apoptosis. Finally, currently available wine deacidification processes and new proposed solutions based on zymological deacidification by select S. cerevisiae strains will be discussed.Fundação para a Ciência e Tecnologi

Progresso genético e eficiência da seleção de linhagens de terras altas via modelos mistos.

Objetivou-se verificar o ganho genético e o dinamismo dos ensaios preliminares do programa de melhoramento de arroz de terras altas da UFLA, em parceria com a Embrapa Arroz e Feijão e a EPAMIG