초록
<P><B>Abstract</B></P><P><I>Dekkera bruxellensis</I> is an important contaminant yeast of fuel ethanol fermentations in Brazil, whose system applies cell repitching between the fermentative cycles. This work evaluated the addition of potassium metabisulphite (PMB) on yeast growth and fermentative yields in pure and co‐cultures of <I>Saccharomyces cerevisiae</I> and <I>D.？bruxellensis</I> in two situations: addition to the acidic solution in which the cells are treated between the fermentative cycles or to the fermentation medium. In the range of 200–400？mg？l<SUP>−1</SUP>, PMB was effective to control the growth of <I>D.？bruxellensis</I> depending on the culture medium and strain. When added to the acidic solution (250？mg？l<SUP>−1</SUP>), a significant effect was observed in mixed cultures, because the inactivation of SO<SUB>2</SUB> by <I>S.？cerevisiae</I> most likely protected <I>D.？bruxellensis</I> from being damaged by PMB. The physiological response of <I>S.？cerevisiae</I> to the presence of PMB may explain the significant decrease in alcohol production. When added to the fermentation medium, PMB resulted in the control but not the death of <I>D.？bruxellensis</I>, with less intensive effect on the fermentative efficiency. In co‐culture with the addition of PMB, the fermentative efficiency was significantly lower than in the absence of PMB.</P><P><B>Significance and Impact of the Study</B></P><P>This study is the first to evaluate the action of potassium metabisulphite to control the growth of <I>Dekkera bruxellensis</I> in the fermentation process for fuel alcohol production. As near as possible of industrial conditions, the study simulates the addition of that substance in different points in the fermentation process, verifying in which situation the effects over the starter yeast and alcohol yield are minimal and over <I>D.？bruxellensis</I> are maximal. Co‐culture fermentations were carried out in cell‐recycled batch system. The feasibility of using this substance for this specific fermentation is discussed in light of the possible biological and chemical interactions.</P>