Evaluation of the double contamination of Dekkera bruxellensis and Lactobacillus fermentum on the alcoholic fermentation: study of the interactions among the microorganisms and the factors that affect the fermentation aiming the control of contaminations
The research applied to the alcoholic fermentation has been concentrated preferably in problems concerned to bacterial contamination, leaving the wild yeasts(yeasts not inoculated into the process) as a poor studied theme. More recently the presence of the genera Dekkera and Brettanomyces has caused troubles in fermentative processes for ethanol production. No study has evaluated the simultaneous contamination of bacteria and Dekkera in industrial conditions for ethanol production in Brazil by now, the factors that affect the development of these contaminations and especially which is the most efficient management aiming their control. This work will verify the effect of factors (subsrate, fermentation system and cell treatment)on the contaminations by yeasts from the species Dekkera bruxellensis (strains CCA059, CCA077 e CCA155) and bacteria belonging to the species Lactobacillus fermentum. The fermentations will be carried out with the selected strain PE-02. The study of interactions among these microorganisms will be also evaluated regarding the production of metabolites by both culturs (organic acidas and bacteriocines) as well as in the competitivity displayed by the cultures in fermentation conditions (low concentration of sugars,utilization of non-assimilable nitrogen sources by S. cerevisiae and presence of sulfite).
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