Caracterização da levedura Saccharomyces cariocanus G01 como um novo fermento cervejeiro

Abstract

Brazil is the third largest beer market in the world and, despite its remarkable biodiversity, it still relies on imported inputs, mainly hops and brewing yeasts. There is also a growing demand for innovative attributes in beers, not only sensory, such as the use of wild yeasts, products with geographical indication, or sociocultural appeal. In this context, our group has investigated the biotechnological potential of environmental microorganisms, with emphasis on a strain previously isolated from the Atlantic Forest and classified as a new species, Saccharomyces cariocanus. Strain G01, derived from the type strain UFRJ 50816T after successive passages in brewer’s wort, showed promising characteristics for brewing applications. This study aimed to evaluate its fermentative performance and physiological properties desirable in brewing yeasts, such as tolerance to ethanol and hop iso-α-acids, flocculation, H2S production, killer phenotype, and growth temperature range, as well as to test immobilization in alginate for cell reuse and improved fermentation kinetics. In addition, the first partial sequencing of the species was carried out, correlating phenotypic features with genomic data. Strain G01 fermented glucose, sucrose, and maltose within 48–72 h, maintained biomass at 7.5 % v/v ethanol with residual growth at 10%, tolerated 5 to 55 IBU with recovery up to 72 h, and exhibited 41.2 % flocculation, classified as moderate. The killer phenotype was not detected, a feature more commonly found in wine yeasts. H2S production was observed, although this does not preclude its use, since it also occurs in commercial brewing yeasts. Growth occurred between 17 and 28 °C but not at 37 °C, reducing the association with pathogenicity, supported by the absence of production of the virulence-associated enzyme phospholipase. Compared with commercial yeasts US-05 and Nottingham, G01 showed similar performance, although with lower flocculation, resembling yeasts used in Wit and Weiss beer production. Sensory evaluation revealed beers rich in ester aromas, consistent with the presence of ATF1, related to isoamyl acetate synthesis (banana-like aroma), and PAD1/FDC1, involved in the formation of phenolic compounds (clove-like aroma). Immobilization in 1.5 % alginate produced beads of 2.16±0.10 mm and 0.010±0.001 g, containing about 1.0×107 cells/mL, with viability better preserved under refrigeration. Both free and immobilized cells achieved attenuation of 41.2 % and an estimated alcohol content of 2.76 %, with no significant differences in the final outcome, indicating that the main benefit of immobilization occurs during the early stages of fermentation. Altogether, the data confirm the Ale-type profile of G01, with strong potential for the production of aromatic and cloudy beers, typical of Weissbier, and some Belgian styles, such as Witbier. The results support G01 as a national candidate for brewing yeast, with clear prospects for optimization regarding fermentation temperature, hopping regime, and storage protocols for immobilized cells to maximize viability and productivity.