PHYSIOLOGICAL ANALYSIS OF YEAST SACCHAROMYCES CEREVISIAE CELLS BY FLOW CYTOMETRY DURING EXPOSURE TO FURFURAL, AN IMPORTANT FERMENTATION INHIBITOR

Saccharomyces cerevisiae is the preferred microorganism in the ethanol fermentation industry from renewable resources such as lignocellulosic biomass. In the process of obtaining monomeric sugars from lignocellulose trough a combination of physical, chemical and enzymatic treatments of biomass formation of inhibitory compounds occurs among wich furfural is the most abundant (Almeida et al, 2007). S. cerevisiae is relatively tolerant to furfural because it is capable of converting it to the corresponding alcohol with lower inhibitory capability by NAD(P)H dependent reactions (Taherzadeh et al, 1999). Unfortunately these mechanisms of detoxification compete for key enzymes and cofactors needed to bra nch carbon flow to respiration and to ethanol production. Several studies have reported that furfural decreased yeast viability, specific growth rate and volumetric fermentation rate. A recent work (Allen et al, 2010) has shown that furfural induced reactive oxygen species (ROS) accumulation and cellular damage in S. cerevisiae. However the toxicity mechanism of furfural on yeast cells is not yet fully understood. In our study we have conducted a flow cytometry analysis on yeast cells from CEN-PK family in response to treatment with different concentrations of furfural. Exposure to high levels of inhibitor did not caused ROS accumulation but resulted in increased intracellular depolarization and accumulation of dead cells. These results may shed light on the mechanism of toxicity of furfural in yeast and might be useful to improve the inhibitor resistance in S. cerevisiae