# Microbial Dynamics in Sour-Sweet Wine Vinegar: Impacts on Chemical and Sensory Composition
## 3 Traditional Balsamic Vinegar Yeasts and Alcoholic Fermentation
### Non-Zygosaccharomyces Strains
stellata_ has been isolated in must from botrytized grapes, wines produced from overripe grapes, and cooked musts associated with TBV [18; 55]. _C. stellata_ presents a strong fructophilic character [56; 57], presenting a considerably lower fermentation rate for glucose than for fructose. [PERSON] et al. [58] detected the presence of the Fiz1 transporter as a requirement for fructophily in _S. bombicola_ (the anamorph of _C. bombicola_ and the synonym of _Torulaspora bombicola_ and _C. bombicola_[59]. Fiz1 is a definite fructose carrier codified by the FFZ1 gene [60]. Besides fermenting fructose, _C. stellata_ yeast species are characterized by low fermentation rates and a high production of secondary metabolites, such as acetaldehyde, acetoin, glycerol, and succinic acid [61] (Table 1). Regarding glycerol formation, the low alcohol dehydrogenase activity and high glycerol-3-phosphate dehydrogenase activity cause a strong deviation of the metabolic pathways toward glycerol production [61]. _C. stellata_ yeast species are also interesting due to their ability to produce a variety of enzymes in wine, namely, polygalacturonase and pectin methyl esterases [62], proteases [63], cellulases and hemicellulose [63; 64], and \(\beta\)-glucosidaseases [65], giving the wine flowery and fruity aromas as documented by [PERSON] et al. [66] (Table 1). All the features mentioned above make _C. stellate_ an interesting yeast able to promote pleasant aromas in traditional balsamic vinegar. Another Candida species, also found in balsamic vinegar is _Candidia lactis-condensi_. This yeast has been isolated from high-sugar wines (Tokaj Essence wines with a sugar concentration ranging from 365 to 752 g/L) [67]. _C. lactis-condensi_ and _C. zemplinia_ were recently transferred to the _Starmerella_ genus, a genus that anchorages yeast species that occur frequently on flowers and flower-visiting insects [67; 68]. _Hanseniuspora vallyensis_ is an uncommon yeast frequently found in TBV [16]. This yeast is also able to survive and proliferate in a demanding environment that has high acid and sugar content and is rich in pectins [16]. _H. vallyensis_ presents substantial pertincolytic activity [69], justifying its prevalence in TBV. This yeast produces low levels of ethanol yet forms significant amounts of acetate esters, such as ethyl and phenyl-ethyl acetate [70], giving the vinegar interesting glue- and rose-like aromas (Table 1). In wine fermentation, _H. osmophila_ presents a glucophilic nature and may harm both the development and fermentation rate of _Saccharomyces_ populations [71]. Generally, _H. osmophila_ produces high levels of ethanol and ethyl acetate [71]. Selective fermentation of glucose is one important characteristic of a yeast strain for TBV production. This is an attractive feature considering that the most osmotolerant species found in the TBV process show, in general, a fructophilic metabolism, resulting in glucose crystallization in the vinegar [16]. It is well known that _Saccharomyces_ strains are glucophilic, so this yeast strain is also important for TBV production [72].