Leveduras não-Saccharomyces: aplicação na produção de cerveja e potencial probiótico

Abstract

The current beer market constantly demands new products and technologies. Beers produced with local ingredients, new flavors, low-calorie beers with low or no alcohol content are a trend in the beer business. The application of different bacteria and yeast strains commercially available, or those present on the surface of fruits or inside maturation barrels, contribute to obtaining unique aromas and specific fermentative characteristics in beers, and in addition, other interesting attributes can be identified in these microorganisms, such as probiotic and antagonist activity against pathogens. Brewers have sought to use non-conventional (or non-Saccharomyces) yeasts as alternatives to obtain new flavors, texture, acidity and contamination control in their processes. Thus, the objective of this work was to identify the diversity of microorganisms present in mixed-fermentation beers, with the main focus on non-Saccharomyces yeasts. Moreover, isolate and identify non-Saccharomyces yeasts from sources such as flowers, fruits and leaves, physiologically characterizing them focusing on important characteristics for the fermentation of beer worts. In addition, evaluate the probiotic potential of the strains, exploring attributes such as antimicrobial activity agains food pathogens, auto-aggregation capacity, co-aggregation, tolerance to adverse conditions found in the gastrointestinal tract, and finally, evaluate the response induced in immune system cells when incubated with yeasts. Twenty samples of mixed starter cultures, spontaneous and non-spontaneous fermentation beers, were used to determine their metagenome, in which were identified 26 species of fungi and 140 species of bacteria, proving that several microorganisms are able to participate in this fermentation process, including a large presence of non-Saccharomyces yeasts, such as Brettanomyces, Pichia, Issatchenkia, Wickerhamomyces, among others. It was possible to isolate and characterize nonSaccharomyces yeasts from environmental samples, especially Moniliella megachiliensis, Pichia kluyveri, Hanseniaspora uvarum, Candida intermedia, which showed different characteristics from most of the commercially available S. cerevisiae strains for beer production, such as tolerance to very acidic pHs (pH ≤ 3.0), high ionic stress (≥ 5% NaCl), high incubation temperatures (37 °C), and the production of characteristic aromas. It was identified in these isolates an auto-aggregation capacity with levels above 83% in different incubation temperatures (18, 28 and 37 °C), co-aggregation with Listeria monocytogenes and Escherichia coli between 50 – 68%), growth inhibition of pathogens, and the induction of mRNA transcription of cytokines, transcription factors and receptor molecules by macrophages stimulated with live yeast cells and their derivatives (heat-killed cells, culture supernatant and DNA). Therefore, it was concluded that non-Saccharomyces yeasts showed potential for application in beer production, it being described here the yeasts M. megachiliensis, P. kluyveri, H. uvarum and C. intermedia, which also provoke interest of new studies for determination and confirmation of their probiotic activity.