Sulfur Dioxide Treatment Alters Wine Microbial Diversity and Fermentation Progression in a Dose-Dependent Fashion

Abstract

The use of sulfur dioxide (SO₂) as an antimicrobial in winemaking is a well-established, common practice. Although much is known about the antimicrobial effects of SO₂ at single concentrations, little is known about its effects on microbial growth dynamics across a range of concentrations or when used in conjunction with yeast inoculation. Using high-throughput marker-gene sequencing, we investigated the cumulative impacts of yeast inoculation and SO₂ treatments across a broad concentration range (0 to 150 mg/L SO₂) on the bacterial and fungal communities in wine fermentations. Our results indicated a dose-dependent effect of SO₂, with lactic acid bacteria and Gluconobacter proliferating in fermentations with <25 mg/L SO₂, but other bacteria and fungi were unaffected by the SO₂ addition. Microbial profiles stabilized at concentrations ≥25 mg/L SO₂, and fermentation performance decreased at higher concentrations (100 to 150 mg/L SO₂). Yeast inoculation alone conferred a stabilizing effect, reducing the bacterial growth observed in unsulfited fermentations, but this effect was not additive with an increase in SO₂ concentrations.