 IVES 9 IVES Conference Series 9 Assessment of wine non-Saccharomyces yeast strains as promising producers of glutathione

Assessment of wine non-Saccharomyces yeast strains as promising producers of glutathione

Abstract

AIM: Glutathione (GSH) is a non-protein thiol naturally present in grape berries and produced by yeasts during fermentation. It has a strong antioxidant activity, thus can be added during winemaking to limit the oxidative phenomena of wine, preserving sensory characteristics and stability, ultimately promoting a healthier product by reducing the need for SO₂ addition. A promising alternative approach could be the use of yeast starter cultures high-producers of this compound in situ, during the fermentation process, in substitution of external GSH addition. Since this activity in non-Saccharomyces yeasts is currently poorly investigated, the aim of this research was to evaluate the ability of three strains of non-Saccharomyces (NS) yeasts to produce GSH, both in synthetic media and in fresh grape must.

METHODS: Lachancea thermotolerans SOL13, Metschnikowia sp. FIANO12, and Starmerella bacillaris MALV45 were tested in single or sequential inoculations,with Saccharomyces cerevisiae EC1118, in synthetic grape juice (SGJ) or in Pinot Grigio grape must, under static conditions, or in a medium optimized for GSH production (MGSH) in agitation (200 rpm). GSH concentration was determined using the Glutathione Assay Kit (Sigma-Aldrich). Population dynamics was evaluated by plate count and biomass dry weight, and fermentation kinetics through weight loss measurement.

RESULTS: A variability in GSH production was found among individual strains and growth conditions. Metschnikowia sp. FIANO12 showed the highest intracellular accumulation of GSH when cultivated alone in both synthetic media, and, as expected, higher levels in the optimized MGSH than in SGJ (4.59 vs. 0.19 nmol GSH/mg cells, respectively). In wine, fermentations with S. bacillaris MALV45 had the highest concentration of intracellular GSH, but the lowest content of wine-dissolved GSH. The maximum level of extracellular GSH (21 mg/L) was obtained in the sequential fermentation with L. thermotolerans SOL13, a significant increase compared to the control singly inoculated with S. cerevisiae.

CONCLUSIONS:

This study highlights a new potential interesting feature of NS yeasts to positively modify wine composition. The tested native strains, with previously demonstrated interesting oenological traits, showed a good capacity to accumulate GSH and to increase the concentration of this antioxidant compound in wine. Thus, the strategy of multi-starter fermentation can be a valuable tool to achieve a lower input winemaking. Future investigations are needed to assess the long-term stability of wine made from multi-starter fermentations with NS yeasts producers of GSH.ACKNOWLEDGEMENTS: We thank Nicolò Bersani for laboratory assistance.

DOI:

Publication date: September 3, 2021

Issue: Macrowine 2021

Type: Article

Authors

Renato L. Binati, Wilson J.F. LEMOS JUNIOR, Sandra TORRIANI

Department of Biotechnology, University of Verona, Italy, Department of Biotechnology, University of Verona, Italy, Department of Biotechnology, University of Verona, Italy

Contact the author

Keywords

Glutathione production, multi-starter fermentation, non-saccharomyces yeasts, saccharomycescerevisiae, winemaking, wine quality

Citation

YEAST DERIVATIVE PRODUCTS: CHARACTERIZATION AND IMPACT ON RIBOFLAVIN RELEASE DURING THE ALCOHOLIC FERMENTATION

Light-struck taste (LST) is a wine fault that can occur in white and sparkling wines when exposed to light. This defect is mainly associated to the formation of methanethiol and dimethyl disulfide due to light-induced reactions involving riboflavin (RF) and methionine [1]. The presence of RF in wine is mainly due to the metabolism of yeast [2] which fermenting activity can be favoured by using yeast derivative products (YDPs) as nutrients. Nonetheless, a previous study showed the addition of YDPs before the alcoholic fermentation (AF) led to higher concentrations of RF in wines [3]. Due to the widespread use of YDPs in the winemaking process, this study aimed to understand the possible relation between the content of RF in wine and the YDP adopted as nutrient for AF.

Qualitative modelling of factors influencing the development of Black rot, for the prediction of damage to bunches

Vines are one of the most pesticide-intensive crops in France, and reducing their use is a major challenge for both the environment and human health.

The effect of ozonated water treatment on the metabolic profile and resistance of vines to Downy and powdery mildew

Ozone is a potent oxidizing compound that quickly decomposes into oxygen without residues. Previous works reported that ozone is not only a disinfectant that directly harms the pathogens of the vine but also activates systemic defense systems in the plant by activating oxidative stress. We assume these systemic defense mechanisms are essential to the vines’ resistance to downy and powdery mildew (Plasmopara viticola & Erysiphe necator, respectively). The goals of the research are to examine the effect of spraying with ozone water on the plant’s resistance against the mentioned pathogens as well as to characterize the metabolic profile of the plants treated with ozone as well as physiological characteristics in the vines such as the level of Photosynthesis and crop yield. Vines in the vineyard sprayed with ozone water at concentrations of 2 and 4 PPM weekly and biweekly, untreated control & conventional spray. Leaves were taken from vines 2,4,7,9 and 11 days after exposure to ozone and inoculated with the pathogens.

Evaluation of methods used for the isolation and characterization of grape skin and seed, and wine tannins

Validation of the phloroglucinolysis and RP-HPLC method showed selectivity and repeatability within acceptable limits for all investigated matrices. Recovery of polymeric phenols by SPE was also acceptable.

Factors influencing the production of the antioxidant hydroxytyrosol during alcoholic fermentation: Yeast Assimilable Nitrogen and Sugar content.

Hydroxytyrosol (HT) is well known for its potent antioxidant activity and anticarcinogenic, antimicrobial, cardioprotective and neuroprotective properties. One possible explanation to its origin in wines is the synthesis from tyrosol, which in turn is produced from the Ehrlich pathway by yeasts. This work aims to explore the factors that could increase the final content as the initial concentration of yeast assimilable nitrogen (YAN) and sugar. Two different concentrations of YAN were proved between 210mg/L and 300 mg/L. Additionally, two different concentrations of sugar were used: 100g/L and 240 g/L. Alcoholic fermentations in synthetic must were performed with the strain QA23.