No abstract

Characterization of non-conventional yeasts for beer crafting The booming in the craft beer market worldwide has demanded innovations to bring up distinctive products. An approach that stands out in this context is the use of non-conventional yeasts in controlled beer fermentation processes. To have better outcomes in this scenario, it is essential that the producer knows the capabilities and limitations of those yeasts. Thus, this study aimed to assess essential and complementary physiological traits of one strain of Brettanomyces anomalus and one of Torulaspora delbrueckii for beer brewing, comparing them with two Saccharomyces cerevisiae strains already used in commercial breweries. The characteristics assessed were chromosome profile (karyotyping technique), growth capacity in different substrates and carbon sources, as well as under different concentrations of ethanol and hop compounds, the capability of sporulation, flocculation, hydrogen sulfide (H2S) production and foam formation and, finally, the fermentation evolution pattern. Differences in the chromosomal profile were observed among the four strains. The potential for H2S production was higher for B. anomalus (WLP640) when compared to T. delbrueckii (WLP603), which had the same potential than S-33 (S. cerevisiae). Both non-conventional yeasts have met the essential physiological traits demanded to carry beer wort fermentation. B. anomalus was able to metabolize many of the assessed carbon sources, as glucose, fructose, sucrose, maltose, maltotriose and cellobiose, while the T. delbrueckii strain was able to grow only in glucose, fructose and sucrose, pointing its potential application for low alcohol beer production, as well as its use in sequential inoculations or co-inoculations with other yeasts. Both showed satisfying growth under alcohol contents of 4% and 8%. T. delbrueckii tolerated higher hop compounds concentration when compared to B. anomalus, that was unable to grow at the highest combined concentrations of ethanol (8% v/v) and α-acids (80 mg/L). The results lead to the conclusion that the yeasts B. anomalus and T. delbrueckii can be explored in beer brewing, provided that an alignment between their physiological traits and the expectations around the beer characteristics are observed.