## 3 Contribution of Selected Yeasts to Emerging Winemaking Demands
### Enhancing the Aroma of Wine
Hansen) resulted in a higher content of isoamyl acetate and a lower content of acetic acid [86]. However, glycerol production could be affected by many variables, such as grape cultivar and nitrogen composition [84]. Among notable non-conventional yeasts, _Lachancea thermotolerans_ is widely used for its high lactic acid and low acetic acid production; hence, it can produce wine without the addition of lactic acid bacteria (LAB) for malolactic fermentation [87]. Furthermore, in _L. thermotolerans_, the Crabtree effect is much weaker than in _S. cerevisiae_, thus contributing to lower ethanol production due to aerobic respiratory metabolism [88]. Moreover, promising results were obtained in evaluating its biocontrol attitude [89]. In Merlot musts, sequential inocula with _L. thermotolerans_ resulted in \"fresher\" wines with reduced acidity and ethanol and increased ester content, mainly ethyl acetate and ethyl lactate, thanks to the presence of lactic acid precursor [90]. Nevertheless, the efficiency of _L. thermotolerans_ in consuming acetic acid can be highly inhibited by high concentrations of sugars (such as glucose) in musts under aerobically limited conditions [87]. Furthermore, scientific evidence reports divergent results about wine aromatic profiles using _L. thermotolerans_, which generally shows a low amount of aromatic compounds compared to _S. cerevisiae_[91]. Frequently used simultaneously with _L. thermotolerans_, _Schizosaccharomyces pombe_ exhibits important characteristics in wines. _S. pombe_, being able to perform mol-alcoholic fermentation, can affect the pH of wine and cause microbiological instability, releasing ethanol and CO\({}_{2}\). Therefore, the availability of _S. pombe_ strains on the market is based on their ability to bio-deacidificate wines [92]. Generally, from an aromatic point of view, fermentation with _S. pombe_ produces a wine with a weak aromatic complexity, a higher concentration of acetaldehyde, propanol, and 2,3-butanediol, and a lower ester content; this aspect is particularly appealing for wines in which the varietal aroma of grapes is preferred above the fermentative aroma [50]. However, when compared to wines fermented with _S. cerevisiae_, no discernible change in flavor has been observed [23]. However, in contrast to _L. thermotolerans_, one of the main negative aspects concerning _S. pombe_ is the high levels of acetic acid production [50]. It is also important to point out that the use of mixed cultures of _L. thermotolerans_ and _S. pombe_ can improve both the structure and color of wine thanks to the production of flavylium ions and polysaccharides [93]. Focusing on the aromatic potential of native yeasts, _M. pulcherrima_ was shown to have a substantial impact on fermentation due to its high release of aromatic compounds, such as varietal thiols, and low production of acetate, ethanol, and acids. However, during the early stages of fermentation, _M. pulcherrima_ can deplete the nitrogen reserve at the expense of _S. cerevisiae_, and thus the potential for nitrogen deficits must be carefully considered to avoid sluggish fermentation [94]. Aromatic complexity attributable to _M. pulcherrima_ can be related to its high beta-glucosidase activity [76]. Moreover, when the inoculum of _M. pulcherrima_ and _Metschnikowia fricticola_ on pre-ferntemative cold maceration in Sangiovese must was evaluated through solid-phase extraction and GC/MS, results revealed higher content of some terpen and \(C_{13}\)-norisoprenoids, nerol (citric aroma), geraniol (geranium), 8-hydroxy-linalool (cis), 3-oxo-\(\alpha\) ionol, and some esters, isoamyl lactate (cream, nut) and ethyl isoamyl succinate, than those found in both controls and wines treated with pectic enzyme [95]. Promising results were obtained by [PERSON] et al. [96], which reported an overall positive aroma profile with a consistent concentration of higher alcohols, including 2-phenylethanol (rose-scented), and by [PERSON] et al. [97], which confirmed a promoted yield of esters and reduced volatile phenols.