## 3 Contribution of Selected Yeasts to Emerging Winemaking Demands
### Reduction of Ethanol Content  
Global warming has critically affected wine production as it has allowed an acceleration in the ripening of grapes and, thus, a higher accumulation of sugars, resulting in higher alcoholic wines [107]. Alcohol consumption is certainly the cause of many health and social problems [108], and consumer attention to health issues has become increasingly pronounced [109]. In this context, the wine industry is increasingly oriented toward promoting wines with reduced ethanol content. Several strategies, including agronomic and fermentation techniques, have been developed; nevertheless, the use of selected yeasts might be a suitable alternative with reduced pressure on wine aroma complexity and quality [110]. In particular, it would be possible to produce wine with lower ethanol by inoculum of Crabtree-negative yeasts (NS yeasts), which would preferentially consume sugars by respiration rather than fermentation. This would allow producers to take advantage of the standardization of partial aeration of must [111]. Among the NS yeasts, _M. pulcherrina_ appears promising in producing ethanol-reduced wines thanks to its aerobic respiratory metabolisms that, in suitable aeration conditions, can aerobically metabolize more than 40% of sugars, thus significantly reducing the ethanol yield [112]. For example, [PERSON] et al. [113] demonstrated that _M. pulcherrina_, in sequential inoculum with _S. cerevisiae_, generated Shiraz wines with approximately 0.9% less ethanol than wines produced using _S. cerevisiae_ in single cultures. A further study described the selection of a strain of _M. pulcherrina_ for the production of lower-ethanol dry wines through a sequential inoculum with _S. cerevisiae_. In detail, based on the inoculation delay of _M. pulcherrina_, white wines (Chardonnay and Semillon blend must) contained between 0.6% and 1.2% less ethanol than wines fermented with _S. cerevisiae_ in single culture [114]. Furthermore, a study carried out by [PERSON] et al. [115] described three strains of _M. pulcherrina_ able to use more than 19 g/L of sugar to produce 1% (_v/v_) of ethanol in grape must. Additionally, _M. pulcherrina_ and _Starmerella bombicola_ are both promising wine yeasts to be used in immobilized forms in sequential fermentation to reduce ethanol content in Verdicchio must, with an ethanol reduction from 1.10 to 1.46% (_v/v_) and from 1.17 to 1.64% (_v/v_), respectively [116]. A recent study confirmed that a sequential fermentation with a native NS, _M. pulcherrina_ CLI 68, and _S. cerevisiae_ CLI 889 generated a reduction of alcohol content around 1.3% in Malvar wine with a higher glycerol content [117]. Furthermore, in Merlot grape juice, sequential inoculum of _M. pulcherrina_ followed by _S. cerevisiae_ resulted in about 11.7% _v/v_ less alcohol production and a 12.3% reduction when observed using _Meyerozyma guilliermondii_. However, inoculation during fermentation with _M. pulcherrina_ alone seems to negatively affect the overall aroma of the final product for producing ethyl acetate, which is lower if co-inoculated with _S. uwarum_[118]. Similar results were obtained by [PERSON] et al. [119] that showed how _M. pulcherrina_ could be a promising yeast, reducing 3.8% ethanol in Riesling must at the expense of isovaleric acid. It has also been shown that if _M. pulcherrina_ can aerobically metabolize more than 40% of sugars, excessive aerobic conditions have an impact on ethyl acetate production. [PERSON] et al. [120] proved that, in Verdicchio must, the combined use of immobilizedcells at a low level (5% (\(w/v\)) of beads) and at an aeration flow of 20 mL/L/min produced a relevant ethanol reduction (1.38% (\(v/v\))), with the production of ethyl acetate still relevant but at an unacceptable level compared to those produced as free cells. Moreover, wines produced with _M. pulcherrima_ and _Z. billi_ under 0.025 VVM (volume of air per volume of culture per minute) aeration resulted in a promising balance between ethanol reduction and volatile profile in Chardonnay must [121].