Growth physiology in bioreactor cultivations of Saccharomyces cerevisiae strains isolated from Brazilian biomes

Abstract

In spite of being the living organism mostly employed in biotechnological processes and also the best studied eukaryote, the yeast Saccharomyces cerevisiae has not yet been well characterized in terms of its natural habitat. Indigenous strains of this species were recently isolated by the research group of Prof. Carlos Rosa (Federal University of Minas Gerais) from Brazilian biomes. Fourteen of these strains were already characterized in our laboratory, in a preliminary and semi-quantitative manner, using shake-flask cultivations. Taking some physiological properties into account (e.g. maximum specific growth rate, ethanol yield on substrate and stress tolerance), four of these strains were selected for a quantitative physiological evaluation using bioreactor cultivations. A common laboratory strain (CEN.PK113-7D) and an industrial fuel ethanol strain (PE-2) will also be used in this study, as references. Bioreactor cultivations allow for a better control over the cultivation conditions, when compared to shake-flask cultivations. For example, the pH and the dissolved oxygen concentrations can be monitored and controlled in the former type of system. This enables a precise comparison among the different yeast strains. Besides this, bioreactor cultivations in chemostat mode further enable controlling the specific growth rate of the cells. With this project, we expect to be able to compare the indigenous strains with the laboratorial and the industrial strains, which will allow us to verify how similar or how different they are from each other, in terms of their macroscopic physiology. Eventually, it will be also be possible to discover new physiological properties in the Saccharomyces cerevisiae species, which could allow their application in biotecnological processes. This proposal is connected to the PITE FAPESP/VALE project 2010/51318-2.