Saccharomyces yeast

Saccharomyces yeasts are rapid fermentors. S. cerevisiae and S. bayanus produce up to 18—20% ethanol. The cells are ovoid to spherical, eUiptical, or elongated (especially under conditions of nitrogen starvation). Vegetative propagation is by multilateral budding. S. uvarum and S. rosei occur earher in the fermentation, when S. rosei may produce up to 6—8% ethanol before being overgrown by the other Saccharomyces yeasts. S. cerevisiae may produce up to 18-20% ethanol (28). 

In addition to malo-lactic fermentation, another biological method for deacidification of high-acid must is to use malic acid-metabolizing Schizo-saccharomyces yeast for the alcoholic fermentation. Benda and Schmidt (33) have selected strains of these yeasts which produce wines with no off-flavors. In using some of these same strains we have also been able to make wines of sound character (18). 

Toon, S.T., et al. Enhanced Cofermentation of Glucose and Xylose by Recombinant Saccharomyces Yeast Strains in Batch and Continuous Operating Modes , Appl Biochem. Bbtechnoi, 63-65, 243 -255 (1997). 

Production of Ethanol from Cellulosic Biomass Hydrolysates Using Genetically Engineered Saccharomyces Yeast Capable of Cofermenting Glucose and Xylose... 

Index Entries Ethanol Saccharomyces yeasts hydrolysate corn stover corn fiber xylose glucose glycerol xylitol. 

Although inoculums of Saccharomyces strains can help to standardize these processes, in the case of Vin Santo, the wine could also be poorer if it is compared with those obtained with spontaneous fermentation (Domizio et ah, 2007 Romani et ah, 2011). In this last, the presence of a higher percentage of non-Saccharomyces yeasts appears to be one of the reasons for the higher complexity found in the relevant wine. 

On this basis, Cavagna et ah (2008) inoculated a must for the production of Vin Santo Trentino with two strains of non -Saccharomyces yeast C. zemplinina and Z. rouxii. Due to their osmophile characters, both of these showed a good performance at the initial stages of the fermentation, and therefore, the Authors considered that these two strains are suitable for the initial stages of fermentation, to lower the sugar concentration of the must. 

Romani et al. (2011) also evaluated the yeast population dynamics and fermentation kinetics, and their influences on the analytical profiles of Vin Santo obtained at industrial scale utilizing in separate trials two non-Saccharomyces yeasts, T. delbrueckii and Z. bailii. These results were compared with those obtained both with spontaneous fermentation and with an inoculum of a S. cerevisiae yeast strain. The standard kinetics of fermentations were observed in all of the trials, also if a higher fermentation rate was observed in the trials inoculated with S. cerevisiae compared to those inoculated with the two non-Saccharomyces yeasts, and in the spontaneous one. A rapid decrease in non-Saccharomyces yeast was observed in the trials inoculated with S. cerevisiae. In these last ones, after 6 months, 18.4% ethanol was reached versus 16% of the trials inoculated with the non-Saccharomyces strains. No substantial differences were seen for the higher alcohols or other byproducts assayed. 

FIGURE 3.10 Yeast growth kinetics of the different genera of non-Saccharomyces yeasts during the fermentation trials for Vin Santo production see Fig. 3.9 legend (elaborated from Domizio et al., 2007)... 

Ciani, M. and Maccarelli, F. (1998). Oenological properties of non-Saccharomyces yeasts associated with wine-making. World ]. Microbiol. Biotechnol. 14,199-203. 

Ciani, M., Comitini, F., Mannazzu, I., and Domizio, P. (2010). Controlled mixed culture fermentation A new perspective on the use of non-Saccharomyces yeasts in winemaking. FEMS Yeast Res. 10,123-133. 

Hansen, H. E., Nissen, P., Sommer, P., Nielsen, J. C., and Arneborg, N. (2001). The effect of oxygen on the survival of non-Saccharomyces yeasts during mixed culture fermentation of grape juice with Saccharomyces cerevisiae. J. Appl. Microbiol. 91, 541-547. 

Sedlak, M. and Ho,N.W.Y. (2004). Production of Ethanol From Cellulosic Biomass Hydrolysates Using Genetically Engineered Saccharomyces Yeast Capable of Cofermenting Glucose and Xylose. Appl. Biochem. Biotechnol., 113-116, 403-416. 

Ho, N. W. Y., Chen, Z. D., and Brainard, A. P., Genetically engineered saccharomyces yeast capable of effective cofermentation of glucose and xylose. Applied Environmental Microbiology 1998, 64 (5), 1852-59. 

Weeks, C. (1969). Production of sulfur dioxide-binding compounds and of sulfur dioxide by two Saccharomyces yeasts. Am. J. Enol. Vitic., 20, 32-39. 

Ugliano, M., Bartowsky E.J., McCarthy, J., Moio, L. Henschke P.A. (2006). Hydrolysis and transformation of grape glycosidicaUy bound volatile compounds during fermentation with three Saccharomyces yeast strains. J. Agric. Food Chem., 54, 6322-6331. 

These various reactions involving yeast metabolites and non-pigmented phenolics are also believed to lead to changes that affect the astringency of tannins (Eglinton et al. 2005). Sensory evaluation of wines made with two Saccharomyces yeast which differed in acetaldehyde production led to differences in mouth-feel attributes associated with tannins, namely grainy, silky, velvet, drying and pucker. 

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