## 3 Results and Discussion
  
* \({}^{1}\) Different levels of significance are indicated with the following symbols: \(<\)1 \(\boldsymbol{\cdot}\)’; \(<\)0.1 \(\boldsymbol{\cdot}\)’; \(<\)0.05 \(\boldsymbol{\cdot}\)’; \(<\)0.01 \(\boldsymbol{\cdot}\)’**; \(<\)0.001 \(\boldsymbol{\cdot}\)’**; \(<\)0.001 \(\boldsymbol{\cdot}\)’**; Values are displayed as mean of a fermentation variant conducted in triplicate (\(n=3\)) plus and minus standard deviation. The compounds vitispirane, 1,8-cineol, nerol, geranyl, nerol, \(\beta\)-ionone, and 1,1,6-trimethyl-1 In a subsequent fermentation, we tested the ability of \(H\). _occidentalis_ to consume malic acid at different starting concentrations. \(H\). _occidentalis_ was inoculated with different versions of the same must with increased amounts of malic acid (2.0-17.1 g/L), and the consumption of this acid was assessed after three and five days (Figure 2). \(H\). _occidentalis_ removes the majority of malic acid after three days of fermentation: in the lower starting concentration of 2.0 g/L, 88% was removed from the must. From the must containing 17.1 g/L of malic acid, H. occidentalis consumed 65% and 73% after three and five days, respectively. Development of acidity as the grape berry matures is an involved process further complicated by rapid climate change, leading to unpredictable yields and thus unexpected acid profiles of must [34]. It is well-known that grapes harvested from cooler climates tend to accumulate more malic acid [35], imparting a tartness to a wine not often desired by consumers. To remove excess malic acid from wine, winemakers generally employ three methods: (i) physical methods which include blending and/or amelioration; (ii) chemical methods by adding bicarbonate; or (iii) biological methods by adding yeast or bacteria [36; 37]. This is because wine \(S\). _cerevisiae_ strains lack a dedicated malate transporter and, with its malic enzyme being located in the mitochondria, cannot effectively remove malic acid from must or wine matrices [38]. Lactic acid bacteria, especially _Oenococcus oeni_, are widely used for converting malic acid to lactic acid, known as malolactic fermentation [39]. Despite their widescale use, it should be noted that lactic acid bacteria are chiefly responsible for the increased biogenic amines levels in wine, which can have several adverse impacts on human health [40]. _Schizosaccharomyces pombe_ or _Zygosaccharomyces_ spp. are shown in literature to effectively remove malic acid due to malo-ethanolic fermentation [41; 42]. A genetically modified \(S\). _cerevisiae_ containing the malate transporter of \(S\). _pombe_ and the malic enzyme of \(O\). _oeni_ was shown to be effective in conducting malolactic fermentation without the addition of lactic acid bacteria [43]. Commercial applications of the abovementioned yeasts are still limited, due to the excess production of acetaldehyde and acetic acid for both non-_Saccharomyces_ yeast species and the limitations of wide-spread use of genetically modified yeast in winemaking. Figure 2: Short Muscaris must fermentations inoculated with \(H\). _occidentalis_ containing additions of malic acid. Malic acid concentrations were determined after three and five days of incubation. This work is, to our knowledge, the first report of an apiculate yeast showing meaningful consumption of malic acid in an oenological setting, and it warrants further exploration. Apart from wine, this feature of _H. occidentalis_ could be useful for the fermentations of other fruit musts where the malic acid content is much higher, such as in apple (ranging from 3-7 g/L) or sweet cherries (which can reach 15 g/L of malic acid) [44]. Further work should include exploring strategies that could mitigate the ethyl acetate production by this species. It has been shown that a simultaneous inoculation of _Hanseniospora uvarum_ and _S. cerevisiae_ co-partners instead of a sequential inoculation could lead to a dramatically different aroma profile, including less ethyl acetate [45]. It has been shown that _S.