Resposta ao estresse Ãcido em leveduras da fermentaÃÃo alcÃolica industrial

AUTOR(ES)

HÃlio Fernandes de Melo

DATA DE PUBLICAÇÃO

2006

RESUMO

Fuel-ethanol fermentation process includes a continuous recycle of the yeast biomass, with yeast cell being exposed to low pH values. It promotes acidic stress that leads to a decrease in cell viability. The aim of his work is to study the factors responsible for cell resistance to acid stress from the identification of yeast gene that are responsive to this stress and the isolation and characterization of inorganic acid-resistant mutant. In the first step, the S. cerevisiae strain JP1 was isolated from fermented must by its dominance in the process of several distilleries. This strain showed the same phonotypical response to industrial stresses (acidic and ethanolic) as the commercial strain PE-2. JP-1 cells were tested for growth and fermentation capacity in acidic mineral medium and the results showed that low pH did not affected those parameters. Further, by 1% of the yeast genes of the laboratory strain JT-95 presented modification in he expression pattern, 35 genes repressed and 28 genes induced by sulphuric acid. However, we did not observed any direct correlation between gene expression and the known mechanism of stress resistance. It suggests that acid stress might induce a multifactorial mechanism in yeast. At last, an inorganic acid-resistant mutant was isolated from JP-1 cells. This mutant grown in acidified medium at pH 2, but similar to its parental did not grow in the presence of organic acid (sorbate). This result shows that cell resistance for those two types of acids might be mediated by different mechanisms. Global gene expression analysis of this mutant can bring interesting clues on the celullar mechanism of resistance to inorganic acids

ASSUNTO(S)

micologia saccharomyces cerevisiae, resposta ao estresse, estresse Ãcido, fermentaÃÃo alcoÃlica industrial saccharomyces cerevisiae, stress response, acid stress, industrial fermentation

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