Characterization of Saccharomyces Strains Isolated from “Kéknyelű” Grape Must and Their Potential for Wine Production

Abstract

Novel wine yeast strains have the potential to satisfy customer demand for new sensorial experiences and to ensure that wine producers have strains that can produce wine as efficiently as possible. In this respect, hybrid yeast strains have recently been the subject of intense research, as they are able to combine the favourable characteristics of both parental strains. In this study, two Saccharomyces “Kéknyelű” grape juice isolates were identified by species-specific PCR and PCR-RFLP methods and investigated with respect to their wine fermentation potential. Physiological characterization of the isolated strains was performed and included assessment of ethanol, sulphur dioxide, temperature and glucose (osmotic stress) tolerance, killer-toxin production, glucose fermentation ability at 16 °C and 24 °C, and laboratory-scale fermentation using sterile “Kéknyelű” must. Volatile components of the final product were studied by gas chromatography (GC) and mass spectrometry (MS). One isolate was identified as a S. cerevisiae × S. kudriavzevii hybrid and the other was S. cerevisiae. Both strains were characterized by high ethanol, sulphur dioxide and glucose tolerance, and the S. cerevisiae strain exhibited the killer phenotype. The hybrid isolate showed good glucose fermentation ability and achieved the lowest residual sugar content in wine. The ester production of the hybrid strain was high compared to the control S. cerevisiae starter strain, and this contributed to the fruity aroma of the wine. Both strains have good oenological characteristics, but only the hybrid yeast has the potential for use in wine fermentation.

A Method for Improving Microbial Conversion of Diosgenin and Separation and Identification of the Product

“…The 13 C-NMR spectrum lacks C-5, C-6 olefinic carbon signals, and even C-3 tertiary carbon-oxygen signals, but has an extra carbonyl group signal (δ C 213.3). In addition, ring A and ring B's signals in the 13 C-NMR spectrum changed greatly, while the other signals were nearly unchanged. Therefore, it is speculated that this compound may be a diosgenin derivative with the 5,6-position double bond reduced and the 3-position hydroxyl group oxidized to a ketone group.…”

“…Diosgenin standard and sample (30 mg each) were added to nuclear magnetic resonance tubes with a diameter of 5 mm and dissolved in 0.6 mL of chloroform-d using sonication [20]. 1 H-NMR, 13 C-NMR, and distortionless enhancement by polarization transfer (DEPT) were carried out on a nuclear magnetic resonance spectrometer with tetramethylsilane (TMS) as the standard material [21].…”

“…ITS rDNA sequences were amplified using PCR. PCR was performed as follows: (1) the initial denaturation temperature was 94 • C for 5 min; (2) 30 cycles, each cycle 94 • C for 30 s, 55 • C for 30 s, 72 • C for 1 min; (3) the terminal extension step was kept at 72 • C for 5 min [13]. PCR products were sent to China Beijing Aoko Biotechnology Co., Ltd. and purified for sequencing.…”

“…Olefinic protons (δ H 5.28, brs, 1H) in the low field indicated that one had an olefinic fragment. In total, 27 carbon signals appeared in the 13 C-NMR spectrum. The DEPT experiment differentiated them into four methyl groups (δ C 19.4, 17.2, 16.3, and 14.5), nine methines (including an olefinic methine (δ C 121.5)), two oxygenated methines (δ C 80.9 and 71.8), and four quaternary carbons (including an olefinic quaternary carbon (δ C 141.0), a bi-oxygenated quaternary carbon (δ C 109.3) and two aliphatic quaternary carbons (δ C 40.3 and 36.6)).…”

Tannin-Tolerant Saccharomyces cerevisiae Isolated from Traditional Fermented Tea Leaf (Miang) and Application in Fruit Wine Fermentation Using Longan Juice Mixed with Seed Extract as Substrate

“…Saccharomyces cerevisiae has been widely used for food applications such as winemaking, baking, and brewing [1]. In particular, various strains of S. cerevisiae play a crucial role in the qualitative properties of alcoholic beverages by enhancing the nutritional composition and sensory qualities of the final product [2,3]. Fermented tea leaf, or Miang, is a traditional food of northwestern Laos PDR.…”