Identification of Dekkera bruxellensis as a major contaminant yeast in continuous fuel ethanol fermentation

To identify and characterize the main contaminant yeast species detected in fuel-ethanol production plants in Northeast region of Brazil by using molecular methods. Total DNA from yeast colonies isolated from the fermentation must of industrial alcohol plants was submitted to PCR fingerprinting, D1/D2 28S rDNA sequencing and species-specific PCR analysis. The most frequent non-Saccharomyces cerevisiae isolates were identified as belonging to the species Dekkera bruxellensis, and several genetic strains could be discriminated among the isolates. The yeast population dynamics was followed on a daily basis during a whole crop harvesting period in a particular industry, showing the potential of D. bruxellensis to grow faster than S. cerevisiae in industrial conditions, causing recurrent and severe contamination episodes. The results showed that D. bruxellensis is one of the most important contaminant yeasts in distilleries producing fuel-ethanol from crude sugar cane juice, specially in continuous fermentation systems. Severe contamination of the industrial fermentation process by Dekkera yeasts has a negative impact on ethanol yield and productivity. Therefore, early detection of D. bruxellensis in industrial musts may avoid operational problems in alcohol-producing plants.