Impact of Assimilable Nitrogen Supplementation on Saccharomyces cerevisiae Metabolic Response and Aromatic Profile of Moschofilero Wine

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.

Effects of Different Fermentation and Clarification Methods on the Color, Physicochemical Characteristics, and Aroma Profile of Healthcare Cornus-Kiwifruit Composite Wine

A lack of distinctive features has become a significant factor limiting the development of kiwi wine. However, the rapidly growing trend of healthcare-oriented composite fruit wine with health functions and diverse flavors presents a way to address this issue. A kiwi wine fermentation method was investigated by incorporating the medicinal and edible fruits of Cornus officinalis. The results indicate that adding Cornus officinalis introduced a unique component known as iridoid glycosides to the wine. Additionally, the concentrations of phenols, total iridoid glycosides, and most aroma compounds in the wine increased after the addition of crushed Cornus officinalis following alcoholic fermentation. As the proportion of Cornus officinalis in the kiwi wine rose, so did polyphenolic substances and total iridoid glycosides; however, this diminished the wine's clarity. Additionally, a yeast addition of 200 mg/L demonstrated optimal fermentation capabilities, and a bentonite addition of 1.1 g/L exhibited an outstanding clarifying effect. These results not only enhance nutritional value and quality but also provide a theoretical foundation for the production of high-quality Cornus-kiwifruit composite wine.

Adaptive laboratory evolution of Lachancea thermotolerans for enhanced production of 2-Phenylethanol and 2-Phenylethyl acetate in wine

2-Phenylethyl alcohol (2-PE) and 2-phenylethyl acetate (2-PEA), responsible for "rose," "fruity" and "floral" aromas in wine, are derived from L-phenylalanine (L-Phe). L. thermotolerans, a common yeast used in wine fermentation, has a limited ability to utilize L-Phe, restricting 2-PE and 2-PEA production. This study aimed to evolve an L. thermotolerans A38 strain with enhanced L-Phe utilization through ALE, in order to increase the production of the wine aroma compounds 2-PE and 2-PEA. After 200 generations of adaptive laboratory evolution (ALE), four mutants were selected, exhibiting an 82.8 % increase in 2-PE (from 15.06 to 28.22 mg/L) and a 2.07-fold increase in 2-PEA (from 75.73 to 157.27 μg/L) in chemically defined grape juice medium (CDGJM). The evolved strains also showed improved tolerance to high sugar concentrations, SO2, ethanol, and pH. In wine micro-vinification, they produced 14.02-fold (from 47.63 to 667.96 mg/L) more 2-PEA and 4.10-fold more 2-PE than the original strain, surpassing the commercial yeast CT10. This study demonstrates ALE as an effective strategy for boosting 2-PE and 2-PEA production in wine.

Effect of different nitrogen source and Saccharomyces cerevisiae strain on volatile sulfur compounds and their sensory effects in chardonnay wine

Three commercial Saccharomyces cerevisiae strains with low, medium, and high H2S-producing capacity were chosen to investigate the effect of yeast assimilable nitrogen (YAN) levels and composition on volatile compounds in a chemically defined medium, specifically high, medium, and low initial YAN levels with varying proportions of DAP or sulfur-containing amino acids (cysteine and methionine). The results revealed that the initial YAN containing a larger proportion of diammonium phosphate resulted in a higher YAN consumption rate during the early stages of fermentation. The yeast strain had a greater effect on the volatiles than the YAN level and composition. Keeping the total YAN constant, a higher proportion of sulfur-containing amino acids resulted in a considerably higher production of 3-methylthiopropanol. The sensory impact of three key volatile sulfur compounds was investigated in a Chardonnay wine matrix, indicating that 3-methylthiopropanol at subthreshold or greater concentrations was effective in enhancing the cantaloupe aroma.

Insight into the growth and metabolic characteristics of indigenous commercial S. cerevisiae NX11424 at high and low levels of yeast assimilable nitrogen based on metabolomic approach

Yeast assimilable nitrogen (YAN) is one of the important factors affecting yeast growth and metabolism. However, the nitrogen requirement of indigenous commercial S. cerevisiae NX11424 is unclear. In this study, metabolomics was used to analyze the metabolite profiles of the yeast strain NX11424 under high (433 mg/L) and low (55 mg/L) YAN concentrations. It was found that yeast biomass exhibited different trends under different YAN conditions and was generally positively correlated with the initial YAN concentration, while changes of key biomarkers of yeast strain NX11424 at different stages of fermentation showed a similar trend under high and low YAN concentrations. The YAN concentration affected the metabolite levels of the yeast strain NX11424, which resulted in the significant difference in the levels of pyruvic acid, α-oxoglutarate, palmitoleic acid, proline, butane-2,3-diol, citrulline, ornithine, galactinol, citramalic acid, tryptophan, alanine, phosphate and phenylethanol, mainly involving pathways such as central carbon metabolism, amino acid metabolism, fatty acid metabolism, purine metabolism, and energy metabolism. Yeast strain NX11424 could utilize proline to produce protein under a low YAN level. The intracellular level of citrulline and ornithine under high YAN concentration was higher than that under low YAN level. Yeast strain NX11424 is more suitable for fermentation at lower YAN level. The results obtained here will help to rational utilize of YAN by S. cerevisiae NX11424, and is conducive to precise control of the alcohol fermentation and improve wine quality.

Assessment of the volatile and non-volatile profile of Savatiano PGI wines as affected by various terroirs in Attica, Greece

Establishing the concept of terroir in wines, combined with the exploitation of native grape varieties, is considered a viable alternative to produce quality wines for increasing interest in the wine market. The aim of this study is the characterization of Protected Geographical Indication (PGI) Savatiano white wines from different regions of Attica (Greece), through the chemical and sensory description of the aroma of wines and the determination of their phenolic profiles. The wines produced with the same vinification protocol were evaluated using the descriptive sensory analysis method while they underwent profiling of volatile and phenolic compounds by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) respectively. The presence of regional differences within the wines was also explored, elaborated with variables that contribute to their differentiation, such as soil type, monthly average temperature, and rainfall. Volatile and sensory profiles of the wines separated the regions and confirmed that sub-regional differences attributed mainly to soil characteristics affect wine aroma. The wines from the east part of Attica were higher in esters, terpenes and higher alcohols with high scores in fruity and blossoms attributes while wines from the north part of Attica presented higher intensity of mineral, nutty and herbaceous attributes. The separations based solely on the phenolic compounds concentration were less clear but a relationship was found between the content of phenolic acids and flavonoids and the studied regions. To our knowledge this is the first characterization of Savatiano PGI wines of Attica generating a fingerprint including chemical composition and sensory aroma characteristics to differentiate wines, combining this pattern with particular sub-regions.