Modulation of Alcohol Content in Wines Using Mixed Cultures

Reducing the alcohol content of wines has received increasing attention, and various strategies have been proposed for this aim. In this study, non-Saccharomyces yeasts isolated from Uruguayan vineyards were screened to identify strains with low ethanol production for use in mixed cultures. Twenty-six strains belonging to six species were evaluated, considering key oenological parameters such as ethanol and glycerol production, glucose and fructose consumption, and absence of organoleptic defects. Based on these criteria, three strains from two genera were selected: Starmerella bacillaris (Sb1 and Sb2) and Metschnikowia fructicola (Mf2). In pure cultures, Starmerella bacillaris showed high sugar consumption along with high glycerol production. Subsequently, co-inoculation and sequential inoculation conditions were tested by combining the selected strains with commercial Saccharomyces cerevisiae (Sc). With Mf2 + Sc sequential inoculation, high sugar consumption, increased glycerol production, and a significant reduction in ethanol were observed compared to the control. For Starmerella bacillaris, only Sb1 achieved consistent alcohol reductions in sequential strategies. With co-inoculation, both strains reduced ethanol by 0.2–1% v/v, although only Sb1 showed complete sugar depletion. Overall, the results demonstrate a marked dependence of fermentation behavior on the strain and highlight the importance of studying biocompatibility and inoculation strategy in mixed cultures.