Figure 4. Fermentation phenotypes in N. atacamensis . A . Growth rate under glucose, fructose and sucrose 2% w/v, and glucose 20% w/vas carbon sources. B . Growth rates under medium supplemented with glucose 2% w/v and ethanol at 6 and 8% v/v. Fermentation results in Synthetic Wine Must (SWM) with a YAN concentration of 300 mg/mL.C . CO2 loss, D . Sugar consumption, E. Ethanol production and F . Glycerol production. EC1118 (grey dots) andN. atacamensis (orange dots).
Based on the results obtained from the microcultures, we proceeded to conduct wine fermentations using monocultures of the N. atacamensis type strain. To assess its fermentation capability, we measured the amount of CO2 lost under Synthetic Wine Must (SWM) conditions, with a YAN concentration of 300 mg/mL. The fermentation assay revealed that ATA-11A-BT was capable of fermenting SWM, achieving a maximum of 75,5 g/L, which was significantly lower compared to the commercially available S. cerevisiae control strain (p -value < 0.05, one-way ANOVA, Figure 4C ). The N. atacamensis type strain exhibited incomplete fermentation, producing ethanol levels of 7.3 ± 0.4% v/v and a having a residual sugar content of 126.7 g/L, comprising 25.8 ± 7.0 g/L of glucose and 100.9 ± 2.5 g/L of fructose. In contrast, the EC1118 control demonstrated a higher ethanol production, reaching up to 14.4 ± 0.2% v/v, with only 23.6 ± 2.4 g/L of residual fructose (Table S8 ). Nevertheless, it is important to note that these values are comparable to those observed with other non-conventional yeasts used in the wine industry, such as Torulaspora delbrueckii , Metschnikowia pulcherrima , Starmerella bacillaris , Wickerhamomyces anomalus and Hanseniaspora vineae (Vejarano & Gil-Calderón, 2021). Altogether, our findings suggest the potential utilization of the novel species N. atacamensis in monocultures or in co-cultures with S. cerevisiaefor wine fermentation.