Caracterização de leveduras isoladas de cerveja tipo Lambic

Abstract

The spontaneous fermentation was responsible for the origin of the beer; in this way the Lambic beers had arisen. The production of craft beer in Brazil has grown, and the purchase and use of yeasts as well. Based on this, the researches on yeast from spontaneous alcoholic fermentation may offer producers new yeast strains options. So, the objective of this work was to analyze the fermentative performance of yeasts found in different stages of a spontaneous fermentation process. For this, eight wild yeast strains (isolated from a spontaneous fermentation process) and two industrial strains were analyzed. Among these yeasts, four belonging to the species Candida glabrata, five to the species Brettanomyces bruxellensis and one to Saccharomyces pastorianus. Cell cultures were used to evaluate yeast growth, consumption of the three carbohydrates mostly found in the brewing wort (glucose, maltose and maltotriose) and the production of ethanol and acetic acid, in addition to a RAPDPCR from the genome of the analyzed strains. The RAPD methodology used was insufficient to differentiate yeasts found in Lambic beer production. Candida glabrata strains were unable to consume maltose and maltotriose while glucose was efficiently fermented. The Brettanomyces bruxellensis strains showed more diversified metabolism: while some of them presented slow and late growth in glucose, others were able to completely metabolize this hexose at the first day of incubation. With the exception of one strain of B. bruxellensis, which consumed more than 95% of the available maltose and maltotriose in the medium, all others had difficulty in metabolizing these two -glycosides. B. bruxellensis strains that consumed the available carbohydrates in the culture medium produced on average 3.8 g L-1 of ethanol. The production of acetic acid was detected in two lines of C. glabrata and three strains of B. bruxellensis, one of which produced between 4.18 and 4.78 g L-1 in the media with the three carbohydrates analyzed. The yeast species S. pastorianus, on the other hand, fermented the three carbohydrates, generating an average of 5.8 g L-1 of ethanol. The data suggest that most of the yeasts isolated from the spontaneous fermentation process would hardly be able to produce, on their own, a beer with the appropriate organoleptic characteristics, given the poor fermentative performance on maltose and maltotriose.