Industrial yeast strains competence in mixed culture with wild flocculent yeast

Abstract In Brazil, the process of ethanol production is well established and there are many factors that may contribute to its efficiency, such as the quality of raw material, process conditions and levels of microbial contamination. During industrial fermentations, the microbial population can be quite dynamic, being able to be totally replaced by wild yeasts of low fermentative efficiency. Thus, the present study aimed to evaluate the fermentative characteristics of a flocculent yeast prevalent in the ethanol production process and the implications of this yeast in the kinetic parameters of the process. A wild yeast strain with a contamination level of 77.4% was found within the colonies isolated from the fermented wine. Fermentative tests were carried out with synthetic sugar cane must with 149 gL-1 of ART with this wild flocculent strain (LFS) and its interaction with the industrial strains Saccharomyces cerevisiae BG-1, CAT-1, FT-858L and PE -2. LFS showed a lower performance in productivity and fermentative efficiency compared to industrial strains. In mixed culture fermentative assays with LFS and the BG-1, CAT-1, FT-858L and PE-2 strains, industrial yeasts showed dominance over wild yeast presenting lower levels of final contamination than initial. However, in the mixed culture assays with PE-2 and LFS with addition of calcium oxide in the must, there were concerning results of fermentative efficiency and productivity, since the LFS yeast started to have a higher dominance than what was previously observed.