The effects of co-culturing non-saccharomyces yeasts with S. cerevisiae on the sugar cane spirit (cachaça) fermentation process

Abstract

Twenty non-Saccharomyces strains were previously tested in pure culture for their ability to grow in 12 % ethanol, their β-glucosidase activity, flocculation, glycerol, ethanol and acetic acid production, fermentation kinetics and their production of volatile compounds. Of these 20 strains, three strains, namely, Pichia anomala UFLA CAF70, P. anomala UFLA CAF119 and Pichia caribbica UFLA CAF733, were evaluated in co-culture with Saccharomyces cerevisiae UFLA CA11. Of the mixed inocula, the mixture of P. caribbica UFLA CAF733 and S. cerevisiae UFLA CA11 gave the highest ethanol concentration (75.37 g/L), the lowest levels of residual glucose (1.14 g/L) and fructose (19.92 g/L), and the highest volumetric productivity (Q p) of ethanol. Twenty-three minor volatile compounds were identified in the fermented sugar cane juice. The mixed culture of P. caribbica UFLA CAF733 and S. cerevisiae UFLA CA11 gave the highest concentration of volatile compounds with good sensory descriptors; these compounds included ethyl esters (290.13 μg/L), acetates (715.21 μg/L) and monoterpenic alcohols (195.56 μg/L). This mixed culture also gave the lowest concentration of volatile acids (1774.46 μg/L) and aldehydes (121.10 μg/L). In principal component analysis, the mixed inoculum of UFLA CAF733 and UFLA CA11 was positively characterized by ethyl hexanoate, 2-phenylethanol, linalool, nonanoic acid, ethyl butyrate, phenylethyl acetate, diethylsuccinate, hexanoic acid, and geraniol. In conclusion, we found that clear improvements could be achieved in the fermentation process with mixed, rather than pure, S. cerevisiae culture. The use of the non-Saccharomyces strain P. caribbica UFLA CAF733 in co-culture with S. cerevisiae UFLA CA11 may therefore be an interesting means by which to improve the quality of cachaça.