## 2 Materials and Methods
### Preparation of the Yeats  
Five non-_Saccharomyces_ yeasts were used in this experiment: _T. delbrueckii_ (BIODIVA(r)), _M. pulcherrima_ (FLAVIA(r)), and _L. thermotolerans_ (LAKTIA(r)) were purchased from Lallemand Inc. (Montreal, Canada), _P. kluyveri_ (Frootzen(r)) was purchased from CHR Hansen (Hoersholm, Denmark) and _S. pombe_ (Atecrem 12H(r)) was purchased from BioEnologia 2.0 (Oderzo, Italy). _Saccharomyces cerevisiae_ var. _bayanus_ (Lalvin EC1118(r)) purchased from Lallemand Inc. was used as a control. _Torulspora delbrueckii_, _M. pulcherrima_, _L. thermotolerans_, and _S. cerevisiae_ were rehydrated according to the manufacturers' protocols, while _S. pombe_ in cream form and _P. kluyveri_ frozen at \(-45\,^{\circ}\)C were added directly to the must. _Torulspora delbrueckii_, _M. pulcherrima_, _L. thermotolerans_, _S. pombe_, and _S. cerevisiae_ yeasts were added in the amounts recommended by the producers, which corresponded to the cell density of approximately 4-5 \(\times\) 10\({}^{6}\) cells/mL. The cell density of _P. kluyveri_ recommended by the producer is much lower, 1 \(\times\) 10\({}^{5}\) cells/mL, but in this work, approximately 1 \(\times\) 10\({}^{6}\) cells/mL were inoculated to keep a similar order of magnitude as for other yeasts. Analysis of Volatile Aroma Compounds by Headspace Solid-Phase Microextraction and Gas Chromatography-Mass Spectrometry  
Volatile aroma compounds were extracted from grape must by headspace solid-phase microextraction (HS-SPME) by the modified method proposed by [PERSON] et al. [24]. Prior to analysis, 7 uL of 5% sulfurous acid (Agorlit, Litija, Slovenia) and 50 uL of sodium azide (VWR BDH Prolabo, Radnor, SAD) were added to inhibit oxidation and microbial activity, respectively, and samples were centrifuged at 4000 rpm at 4 \({}^{\circ}\)C for 5 min using a laboratory centrifuge Universal 320 R (Hettich, Westphalia, Germany). Half a milliliter of the supernatant was placed in a 10 mL glass vial containing 3.45 mL of deionized water. A gram of ammonium sulphate and 50 uL of internal standards solution (2-octanol at 0.84 mg/L, 1-nonanol at 0.82 mg/L, and heptanoic acid at 2.57 mg/L) were added. The samples were incubated for 15 min under stirring at 800 rpm, and the extraction using a divinylbenzene/Carboxen/polydimethylsiloxane (DVB/CAR/PDMS; StableFlex, 50/30 um, 1 cm; Supelco, Bellafonte, PA, USA) fiber took place for 40 min at 40 \({}^{\circ}\)C. When the extraction finished, the fiber was inserted into the GC/MS injector port at 248 \({}^{\circ}\)C for 10 min, with the first 3 min in splitless mode. For the identification and quantification of volatile aroma compounds a Varian 3900 gas chromatograph (GC) coupled to a Varian Saturn 2100T ion trap mass spectrometer (MS) (Varian Inc., Harbour City, CA, USA) was used. The GC-MS was equipped with an Rtx-WAX capillary column of the following dimensions: 60 m \(\times\) 0.25 mm i.d. \(\times\) 0.25 um d.f. (Restek, Belafonte, PA, USA). The initial column temperature was 40 \({}^{\circ}\)C, then it was increased at 2 \({}^{\circ}\)C/min to 240 \({}^{\circ}\)C, and it remained at this temperature for the next 10 min. The carrier gas was helium with a 1.2 mL/min flow rate. Electron ionization mode (EI, 70 eV) in the range of 20-350 \(m\)/\(z\) was used to acquire mass spectra. A comparison of retention times and mass spectra with those of the pure standards and with those available in the NIST05 library was used for identification. Spectra reverse match numbers RM \(>\) 800 were considered satisfactory. In the cases of RM \(<\) 800, the identification was based on the similarity of the intensities of a quantifier ion and other major ions in the spectra to those in the reference spectra. A solution containing C10 to C28 n-alkanes was injected under the same chromatographic conditions, the linear retention indices were calculated, and the identity of volatile compounds was additionally confirmed by comparison with the retention indices reported in the literature.