Candida zemplinina can reduce acetic acid produced by Saccharomyces cerevisiae in sweet wine fermentations

Abstract

In this study we investigated the possibility of using Candida zemplinina, as a partner of Saccharomyces cerevisiae, in mixed fermentations of must with a high sugar content, in order to reduce its acetic acid production. Thirty-five C. zemplinina strains, which were isolated from different geographic regions, were molecularly characterized, and their fermentation performances were determined. Five genetically different strains were selected for mixed fermentations with S. cerevisiae. Two types of inoculation were carried out: coinoculation and sequential inoculation. A balance between the two species was generally observed for the first 6 days, after which the levels of C. zemplinina started to decrease. Relevant differences were observed concerning the consumption of sugars, the ethanol and glycerol content, and acetic acid production, depending on which strain was used and which type of inoculation was performed. Sequential inoculation led to the reduction of about half of the acetic acid content compared to the pure S. cerevisiae fermentation, but the ethanol and glycerol amounts were also low. A coinoculation with selected combinations of S. cerevisiae and C. zemplinina resulted in a decrease of ~0.3 g of acetic acid/liter, while maintaining high ethanol and glycerol levels. This study demonstrates that mixed S. cerevisiae and C. zemplinina fermentation could be applied in sweet wine fermentation to reduce the production of acetic acid, connected to the S. cerevisiae osmotic stress response.

Fig 1

Dendrogram of similarity constructed taking into consideration the RAPD and SAU-PCR profiles of the C. zemplinina strains used in the present study. Clusters are indicated by Latin numerals.

Fig 2

Growth dynamics of C. zemplinina during fermentation of the must obtained from dried grapes. The results of the 35 strains are reported as minimums and maximums (indicated by the lines) and median values.

Fig 3

Growth dynamics of the S. cerevisiae strains (FB40 [A], ELCF3WC [B], and EC1118 [C]) coinoculated (solid symbols) or sequentially inoculated (empty symbols) with C. zemplinina, as determined on the WLN medium. The mean CFU/ml values ± the standard deviations of five fermentations (each with a different C. zemplinina strain) are shown for each S. cerevisiae, whereas all of the data were combined and are presented as the mean CFU/ml ± the standard deviations for the five selected strains of C. zemplinina. Abbreviations: Cz_C, C. zemplinina in coinoculation; Sc_C, S. cerevisiae in coinoculation; Cz_S, C. zemplinina in sequential inoculations; Sc_S, S. cerevisiae in sequential inoculations.