Developing a novel selection method for alcoholic fermentation starters by exploring wine yeast microbiota from Greece

The use of autochthonous Saccharomyces cerevisiae strains as a strategy to enhance aroma variability and typicity of Savatiano wines; RNAseq-based transcriptome comparison of indigenous strains under winemaking conditions

The connection between wine microbiota and terroir has become increasingly significant in the wine industry in recent years. Indigenous yeasts have emerged as a valuable tool for imparting unique qualities to wine, enhancing the aroma characteristics specific to a given wine-producing region. This study aimed to isolate indigenous Saccharomyces cerevisiae strains from spontaneous fermentations and assess their impact on the fermentative performance, chemical composition, and wine aroma profiles, using two commercial strains serving as controls. Fermentation kinetics, organic acids, ethanol, and glycerol content were monitored daily using HPLC. The produced wines were evaluated for their organoleptic properties and underwent volatile compound profiling using GC-MS. Additionally, the gene transcription patterns of the isolated yeasts and their connection to the resulting oenological traits were further explored, employing RNAseq during fermentation. Our study revealed that native strains supported volatilome, promoted ester and terpene formation, enhanced fruity, floral, and sweet attributes, and contributed to a distinct wine aroma compared to the control ones. Of particular interest were the differences in organic acid metabolism and glycerol formation. Transcriptomes of the indigenous yeasts identified different genomic responses and explained the variations in metabolite production between strains. In conclusion, the data obtained highlights the different transcriptomic and metabolic profiles of the indigenous yeasts isolated during this study. Besides, the importance of understanding yeast genomics and metabolism to achieve promising sensory characteristics and unique wine styles was emphasized, and these insights could contribute to the development of new products while preserving the identity of a region.

The prospect of superior yeast for winemaking: recent successes through bioprospecting

This article provides a selective review of recent reports that describe developments in the pursuit of superior yeast for winemaking through bioprospecting. In recent years, the focus of researchers and starter-culture companies has broadened. No longer are the targets merely strains that are reliable and sensorily inoffensive. Rather, efforts have expanded to seek much greater precision in these age-old targets and/or strains that address aspects of sustainability by enabling reduced waste, fewer chemicals or less energy input.

The impact of simultaneous inoculation with Torulaspora delbrueckii and Hanseniaspora uvarum combined with Saccharomyces cerevisiae on chemical and sensory quality of Sauvignon blanc wines

Non-Saccharomyces yeasts have great potential in improving wine quality, showing personality characteristics, and highlighting the terroir of wine. In this study, we evaluated the impact of simultaneous inoculation with the non-Saccharomyces yeasts Torulaspora delbrueckii or (and) Hanseniaspora uvarum in combination with Saccharomyces cerevisiae (EC1118 or VL3) on the aromatic compounds and sensory quality of Sauvignon blanc wines. The growth of yeast groups in the alcoholic fermentation process was tracked using fluorescence in situ hybridization. The presence of non-Saccharomyces yeast notably impacted the distribution of S. cerevisiae and was related to the species of yeast. The co-fermentation of H. uvarum and S. cerevisiae improved the content of total esters, especially acetate esters. Simultaneous inoculation of T. delbrueckii or (and) H. uvarum significantly increased the content of total terpenes, especially linalool. Similar results were found for some higher alcohols and organic acids. Sensory evaluation showed that the wines mixed fermentation with H. uvarum had significantly tropical fruit aroma characteristics. Citrus and mineral notes, typical aroma characteristics of Sauvignon blanc wine, were enhanced by mixed fermentation strategies with T. delbrueckii or (and) H. uvarum and different S. cerevisiae. Hence, co-fermentation by T. delbrueckii or H. uvarum combined with S. cerevisiae could significantly improve the sensory quality of Sauvignon blanc wine.

New Insights into the Production of Assyrtiko Wines from the Volcanic Terroir of Santorini Island Using Lachancea thermotolerans

Assyrtiko is a rare ancient grape variety of Greece, which is known to produce Protected Designation of Origin (PDO) Santorini white wines. Besides the famous character of the volcanic terroir, Assyrtiko of Santorini is also marked by a low pH value and sharp acidity. The aim of the present study was to apply a new inoculation procedure that modulates the fermentation process by maintaining the unique sensorial characteristics of Assyrtiko wines based on acidity. For this purpose, the Lachancea thermotolerans species, known for the formation of lactic acid, was tested in sequential fermentation with three different Saccharomyces cerevisiae strains. At the end of the fermentation process, implantation control for S. cerevisiae strains (interdelta sequence profile analysis) was performed, oenological parameters were determined according to the OIV protocols, and the volatile compounds produced were measured by gas chromatography-mass spectrometry (GC/MS). Finally, all produced wines were evaluated by quantitative descriptive analysis by two groups of experts; the Greek team of oenologists from Santorini Island specialized in Assyrtiko wines, and the French team of oenologists specialized in wine from Bordeaux. As expected, the inoculated strain was the one that dominated the fermentation process, but nine S. cerevisiae indigenous strains were also identified in the produced wines. Lachancea thermotolerans produced 1 g/L of lactic and also modulated the volatile profile of the wines independently of the S. cerevisiae strain used. The origin of the panelists played an important role in bringing up sensorial traits, such as acidity. Our results led to a new interesting application of L. thermotolerans for white wine production adapted to climate change claims.