Biochemical and molecular characterization of Saccharomyces cerevisiae strains obtained from sugar-cane juice fermentations and their impact in cachaça production

Abstract

Saccharomyces cerevisiae strains from different regions of Minas Gerais, Brazil, were isolated and characterized aiming at the selection of starter yeasts to be used in the production of cachaça, the Brazilian sugar cane spirit. The methodology established took into account the screening for biochemical traits desirable in a yeast cachaça producer, such as no H2S production, high tolerance to ethanol and high temperatures, high fermentative capacity, and the abilities to flocculate and to produce mycocins. Furthermore, the yeasts were exposed to drugs such as 5,5',5"-trifluor-D,L-leucine and cerulenin to isolate those that potentially overproduce higher alcohols and esters. The utilization of a random amplified polymorphic DNA-PCR method with primers based on intron splicing sites flanking regions of the COX1 gene, as well as microsatellite analysis, was not sufficient to achieve good differentiation among selected strains. In contrast, karyotype analysis allowed a clear distinction among all strains. Two selected strains were experimentally evaluated as cachaça producers. The results suggest that the selection of strains as fermentation starters requires the combined use of biochemical and molecular criteria to ensure the isolation and identification of strains with potential characteristics to produce cachaça with a higher quality standard.

FIG. 1.

Geographical location of the five distilleries in Minas Gerais state (Brazil).

FIG. 2.

Electrophoretic karyotype patterns of S. cerevisiae strains isolated from five distilleries.

FIG. 3.

mtDNA RFLP analysis of S. cerevisiae strains isolated from five distilleries.

FIG. 4.

RAPD-PCR profiles prepared by using EI1 and LA1 primers of S. cerevisiae strains isolated from five distilleries. The circle around the 1,600-bp band on strain E22 indicates the unique difference found among the cachaça yeast strains.

FIG. 5.

COX1-PCR profiles by using primers 3L, 3R, 4L, and 5R of S. cerevisiae strains isolated from five distilleries.

FIG. 6.

RAPD-PCR profiles by using EI1 and LA1 primers of S. cerevisiae strains isolated from one distillery in two different years (2001 and 2003).

FIG. 7.

Concentration of isoamyl alcohol in different cachaça samples obtained with selected yeast cells compared to concentrations produced by a commercial strain. The national average values in 2003 and 2005 samples of cachaça produced in Ouro Preto by spontaneous fermentation are also shown.