Physiological and fermentative performance of non-Saccharomyces yeasts isolated from kombucha for beer production.

Abstract

This study aimed to isolate, identify, and characterize kombucha yeasts for beer production. Nineteen yeasts were isolated, and the species Brettanomyces bruxellensis, Galactomyces candidum, Galactomyces sp., Pichia kluyveri, and Saccharomycodes ludwigii were identified. The strains B. bruxellensis L652, P. kluyveri L472, L231, L431, and L131, and S. ludwigii L331 present desired physiological properties for beer production, including tolerance to 6% ethanol, 100 mg/L of iso-α-acid and flocculation capacity. It was selected for wort fermentation at 10 °C and 20 °C. Beers with different chemical characteristics were produced when evaluated at 10 °C and 20 °C for all strains. Minor carbohydrate residuals and higher ethanol concentrations were observed in the beers fermented at 20 °C. All non-Saccharomyces yeasts evaluated produced alcohol-free beers (<0.5%) at 10 °C. At 20 °C, only the yeast P. kluyveri L431 produced non-alcoholic beer (0.24%). The yeasts P. kluyveri L131, L231, and L472 and B. bruxellensis L652 produced beers with reduced alcoholic content (0.6-1.4%), and the strains S. ludwigii L331 produced alcoholic beer (2.45%). Relating acetic acid, the strains P. kluyveri L431 and L472 presented higher concentrations (0.226 g/L and 0.264 g/L, respectively) at 10 °C, while S. ludwigii L331 showed the highest concentration (0.936 g/L) at 20 °C, demonstrating the potential to produce sour beers. These results indicate that evaluating the yeast strain according to the beer style is crucial.