## 4 Discussion
Nonvolatile compounds typically contribute to production of conserved metabolites most easily perceived by sensory analysis of wines such as metabolites that contribute to the perception of sweetness, sourness, and mouthfeel (Figure 6). Previous study reported no more than 25% of tartaric acid degraded by _S. cerevisiae_ and non-_Saccharomyces_ species (_Kloeckera_, _Candidia_, _Schizosaccharomyces_, and _Hansenula_ spp.) which corresponds to our results except _H. uvarum_ PSWCC70 [71]. The association between _H. uvarum_ and degradation of tartaric acid could possibly be yeast strain using, for example, the carbon and energy source regardless of the presence of assimilable sugar [72]. _Hanseniispora opuntiae_ PSWCC64 producing higher concentration of succinic acid with no significant differencewith _S. cerevisiae_ control strain might indicate a larger proportion of fermented sugar was used for the production of succinic acid [73]. Moreover, the trend of acetic acid production by yeast strains was similar to the glycerol production as the production of these two compounds has been linked together. According to these results, although nonvolatile profiles by candidate strains were clustered with control strain on PLS-DA score plot, different productions of nonvolatile compounds indicated that non-_Saccharomyces_ yeasts utilized fermented sugar differently in the metabolic pathway to _S. cerevisiae_. One area of interest in winemaking is strain innovation. Previous works have demonstrated that fermentation-derived metabolites from non-_Saccharomyces_ yeast can contribute to unique volatile characteristics of final wines. We hypothesize that non-_Saccharomyces_ isolates from local wineries can enhance and preserve regionality of final wines. To this end, we used GC-MS coupled with statistical methods that enable visualization of important volatile metabolites that drive differences between candidate strains. Notable differences in volatile wine-associated profile between candidate non-_Saccharomyces_ yeasts and control strain were demonstrated by PLS-DA and Pearson's correlation. We were particularly interested in compounds that drive volatilome changes in non-_Saccharomyces_ strains compared to BY4742 (Figure 7D). High VIP scores indicate important compounds positively correlated to _Hansenispora_ strains PSWCC64 and PSWCC70 were 2-heptanol (V9) having fruity and herbaceous odor, ionone (V42) with floral and fruity odor, and 1-propanol, 3-(methylthio)-(V72) preserved odor of cauliflower and potato, which were negatively correlated to _S. cerevisiae_ BY4742 [74; 75; 76; 77]. This demonstrated the potential of candidate strains in winemaking to increase the complexity of wine aroma which _Saccharomyces_ yeasts were less capable of contributing to wines. Of particular interest in this study, _P. kudriazevii_ PSWCC102 positively correlates with a group of volatiles which is negatively correlated to other candidate strains. This included esters and acetals, such as heptanoic acid, ethyl ester (V30), 2-hexenoic acid, ethyl ester (V31), butane, 1-(1-ethoxyoxy)- (V63), benzaldehyde, 3-methyl- (V60), and butane, 1,1-diethoxy-3-methyl-- (V64) having pleasant fruity and herbaceous aroma [78; 79; 80; 81]. In addition, _P. kudriazevii_ PSWCC102 demonstrates ethanol tolerance (10%) comparable to _S. cerevisiae_ control strain. Therefore, _P. kudriazevii_ PSWCC102 could be a potential candidate for future studies that investigate the sequential or coinoculation of _P. kudriazevii_ during winemaking and production of fruity aroma compounds that are unique to the strain. Others have shown that sequential or coinoculation of non-_Saccharomyces_ yeasts with _S. cerevisiae_ has been demonstrated to increase complexity of wine-important volatiles and sensory qualities [82; 83; 84; 85]. Conducting sensory analysis is also valuable to understand whether coformation could positively influence the sensory qualities and consumer preferences by considering the attributes of taste, flavor, mouthfeel, and color.