Investigating the glutathione accumulation by non-conventional wine yeasts in optimized growth conditions and multi-starter fermentations

Investigating biological mechanisms of colour changes in sustainable food systems: The role of Starmerella bacillaris in white wine colouration using a combination of genomic and biostatistics strategies

This study explores the biological mechanisms behind colour changes in white wine fermentation using different strains of Starmerella bacillaris. We combined food engineering, genomics, machine learning, and physicochemical analyses to examine interactions between S. bacillaris and Saccharomyces cerevisiae. Significant differences in total polyphenol content were observed, with S. bacillaris fermentation yielding 6 % higher polyphenol content compared to S. cerevisiae EC1118. Genomic analysis identified 12 genes in S. bacillaris with high variant counts that could impact phenotypic properties related to wine color. Notably, SNP analysis revealed numerous missense and synonymous variants, as well as stop-gained and start-lost variants between PAS13 and FRI751, suggesting changes in metabolic pathways affecting pigment production. Besides that, high upstream gene variants in SSK1 and HIP1R indicated potential regulatory changes influencing gene expression. Fermentation trials revealed FRI751 consistently showed high antioxidant activity and polyphenol content (Total Polyphenol: 299.33 ± 3.51 mg GAE/L, DPPH: 1.09 ± 0.01 mmol TE/L, FRAP: 0.95 ± 0.02 mmol TE/L). PAS13 exhibited a balanced profile, while EC1118 had lower values, indicating moderate antioxidant activity. The Weibull model effectively captured nitrogen consumption dynamics, with EC1118 serving as a reliable benchmark. The scale parameter delta for EC1118 was 23.04 ± 2.63, indicating moderate variability in event times. These findings highlight S. bacillaris as a valuable component in sustainable winemaking, offering an alternative to chemical additives for maintaining wine quality and enhancing colours profiles. This study provides insights into the biotechnological and fermented food systems applications of yeast strains in improving food sustainability and supply chain, opening new avenues in food engineering and microbiology.

Antioxidant inactivated yeast: High potential of non-Saccharomyces specific metabolome

Understanding the contribution of new natural sources of antioxidant compounds to the stability of wines is of great interest in a context of reduction of sulfites. Here, we investigated the antioxidant potential of selected inactivated non-Saccharomyces yeast (INSY) along with related chemical fingerprints, using combined untargeted UHPLC-Q-ToF MS and DPPH analyses. 4 INSY species were compared to a reference inactivated Saccharomyces cerevisiae yeast (ISY) selected for its high antioxidant capacity. Our results show that, all the INSY can accumulate GSH during the specific production process with yields ranging from +170 % to +360 % compared to the corresponding classical production process. The principal component analysis of the 3511 ions detected by UHPLC-Q-ToF-MS clearly grouped INSY by species, independently of the production process. One INSY exhibited equivalent antioxidant capacity to the control ISY, but with a GSH concentration four times lower (4.73 ± 0.09 mg/g against 20.95 ± 0.34 mg/g, respectively). 73 specific ions presenting strong and significant spearman correlation (rho < -0.6, p-value < 0.05) with the DPPH scores, clustered the most antioxidant INSY and the control Saccharomyces in different groups, indicating that the antioxidant capacity of these two products should be driven by different pools of compounds. These results point out that, GSH alone is not relevant to explain the antioxidant capacity of INSY soluble fractions and other more reactive compounds must be considered, which opens an avenue for the selection new species with great enological potential.

Mixed biofilm formation by Oenococcus oeni and Saccharomyces cerevisiae: A new strategy for the wine fermentation process

Bacterial biofilms have attracted much attention in the food industry since this phenotype increases microbial resistance to environmental stresses. In wine-making, the biofilm produced by Oenococcus oeni is able to persist in this harsh environment and perform malolactic fermentations. Certain viticultural practices are interested in the simultaneous triggering of alcoholic fermentation by yeasts of the species Saccharomyces cerevisiae and malolactic fermentation by lactic acid bacteria. As yet, no data is available on the ability of these micro-organisms to produce mixed biofilms and promote fermentations. Here, the ability of S. cerevisiae and O. oeni to form mixed biofilms on different surfaces found in vinification was observed and analyzed using scanning electron microscopy experiments. Then, following co-inoculation with biofilm or planktonic cells microvinifications were carried out to demonstrate that the mixed biofilms developed on oak allow the efficient completion of fermentations because of their high resistance to stress. Finally, comparisons of the different metabolic profiles obtained by LC-MS were made to assess the impact of the mode of life of biofilms on wine composition.

Emerging biotechnologies and non-thermal technologies for winemaking in a context of global warming

In the current situation, wine areas are affected by several problems in a context of global warming: asymmetric maturities, pH increasing, high alcohol degree and flat wines with low freshness and poor aroma profile. The use of emerging biotechnologies allows to control or manage such problems. Emerging non-Saccharomyces as Lachancea thermotolerans are very useful for controlling pH by the formation of stable lactic acid from sugars with a slight concomitant alcohol reduction. Lower pH improves freshness increasing simultaneously microbiological stability. The use of Hanseniaspora spp. (specially H. vineae and H. opuntiae) or Metschnikowia pulcherrima promotes a better aroma complexity and improves wine sensory profile by the expression of a more complex metabolic pattern and the release of extracellular enzymes. Some of them are also compatible or synergic with the acidification by L. thermotolerans, and M. pulcherrima is an interesting biotool for reductive winemaking and bioprotection. The use of bioprotection is a powerful tool in this context, allowing oxidation control by oxygen depletion, the inhibition of some wild microorganisms, improving the implantation of some starters and limiting SO2. This can be complemented with the use of reductive yeast derivatives with high contents of reducing peptides and relevant compounds such as glutathione that also are interesting to reduce SO2. Finally, the use of emerging non-thermal technologies as Ultra High-Pressure Homogenization (UHPH) and Pulsed Light (PL) increases wine stability by microbial control and inactivation of oxidative enzymes, improving the implantation of emerging non-Saccharomyces and lowering SO2 additions. GRAPHICAL ABSTRACT.

Magnetic fields as inducer of glutathione and peroxidase production by Saccharomyces cerevisiae

Glutathione (GSH) and peroxidase (POD) are biomolecules of interest in the global market; thus, it is desirable to seek ways to increase their production. Magnetic field (MF) application is one of the technologies used in cultivation that has shown promising results to increase bioproducts. Therefore, this study aimed at evaluating the influence of MFs on GSH and POD production by Saccharomyces cerevisiae ATCC 7754. Different periods of MF application (35 mT) were evaluated over 72 h. The highest GSH production was reached in 48 h of cultivation in assays MF 0-24 (155.32 ± 9.12 mg L-1) and MF 0-72 (149.27 ± 3.62 mg L-1), which showed an increase of 121.9 % and 113 %, respectively, by comparison with the control without any MF application. The highest POD activity was achieved when MFs were applied throughout the culture (36.31 U mg-1) and POD productivity of 0.72 U mg-1 h-1. MF application throughout cultivation proved to be a promising strategy since all responses increased, i.e., GSH concentration, GSH productivity, POD activity, and POD productivity increased 113.7 %, 113 %, 20.4 %, and 28.6 %, respectively. This study is one of the first to consider MFs as a viable and low-cost alternative to produce GSH and POD in bioprocesses.

Characterization of Non-Saccharomyces Yeast Strains Isolated from Grape Juice and Pomace: Production of Polysaccharides and Antioxidant Molecules after Growth and Autolysis

Non-Saccharomyces yeasts (NSY) represent a relevant part of must and wine microbiota, contributing remarkably to the composition of lees biomass. Despite a number of studies indicate their capacity to increase wine polysaccharide content, their contribution to wine quality during aging on lees (AOL) has not been well elucidated yet. In the present study, twenty yeast strains (13 non-Saccharomyces and 7 Saccharomyces) were isolated from grape must and pomace and identified by morphologic and genetic characterization. Biomass production, cell growth and the release of soluble molecules (polysaccharides, amino acids, thiol compounds and glutathione) were evaluated after growth and after autolysis induced by β-glucanases addition. Differences between strains were observed for all parameters. Strains that produced higher amounts of soluble compounds during growth also showed the highest release after autolysis. Hanseniaspora spp. showed the greatest production of polysaccharides and antioxidant molecules, and biomass production and cell viability comparable to the commercial S. cerevisiae and T. delbrueckii used as reference. The aptitude of certain NSY to release antioxidants and polysaccharides is an interesting feature for managing AOL through sequential or mixed fermentations or for the production of inactive autolyzed yeasts for winemaking.

Glutathione production by Saccharomyces cerevisiae: current state and perspectives

Glutathione (L-γ-glutamyl-cysteinyl-glycine, GSH) is a tripeptide synthesized through consecutive enzymatic reactions. Among its several metabolic functions in cells, the main one is the potential to act as an endogenous antioxidant agent. GSH has been the focus of numerous studies not only due to its role in the redox status of biological systems but also due to its biotechnological characteristics. GSH is usually obtained by fermentation and shows a variety of applications by the pharmaceutical and food industry. Therefore, the search for new strategies to improve the production of GSH during fermentation is crucial. This mini review brings together recent papers regarding the principal parameters of the biotechnological production of GSH by Saccharomyces cerevisiae. In this context, aspects, such as the medium composition (amino acids, alternative raw materials) and the use of technological approaches (control of osmotic and pressure conditions, magnetic field (MF) application, fed-batch process) were considered, along with genetic engineering knowledge, trends, and challenges in viable GSH production. KEY POINTS: • Saccharomyces cerevisiae has shown potential for glutathione production. • Improved technological approaches increases glutathione production. • Genetic engineering in Saccharomyces cerevisiae improves glutathione production.