CARACTERIZAÇÃO MOLECULAR E BIOQUÍMICA DE CEPAS DE Saccharomyces cerevisiae UTILIZADAS NA CARACTERIZAÇÃO MOLECULAR E BIOQUÍMICA

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

Aiming the molecular characterization of Saccharomyces cerevisiae LBCM 427 strain, selected from fermentations vats of a cachaça distillery, several analysis using polymorphism analysis of DNA for the characterization/discrimination of this and the selvagem strains present in the origin place was used. Results showed that RAPD-PCR, mtDNA, and PCR using complementary primers COXI gene region were not sufficient for distinguishing among them. On the other hand, the chromosomal pattern profile of kariotyping showed to be useful to discriminate the strains studied. These results showed that use of starting strains requires the combined use of biochemical and molecular methods for monitoring start strains. The parental strain LBCM 427, was sporulated and its tetrads were analyzed for physiologic and biochemical stability through successive generations. We selected the strains for: capacity flocculation, no H2S production, 5, 5,5-trifluoro-DL-leucine (TFL) and cerulenin resistance and ability to adapt to stress conditions during fermentation of the sugarcane juice such as high osmotic concentration and temperature. No single segregant was found that kept entirely all the characteristics of the parental strain. In view of this result, a segregant keeping the characteristic of resistance to TFL and cerulenin compounds was selected for analysis of fermentation of sugar cane juice and probable mutation in the LEU4 gene that encodes for alpha isopropylmalate synthase (alpha-IPM). This segregant showed that alpha-IPM activity was not affected by the presence of increasing leucine concentrations (20 mM), and showed a new mutation in the LEU4 gene which has not been previously described in the literature. LBCM 427 and segregant strains were submitted to a small-scale distillation for cachaça production. The parameters analysed were the chemical profile of the product as well as strain ability to adapt to stress conditions during fermentation of the sugarcane juice in artisanal cachaça`s factory. Volatile compounds such as acetaldehyde, ethyl acetate, methanol, n-propanol, isobutyl alcohol, isoamyl alcohol and furfural were quantified by gas chromatography assays. It was found that LBCM 427 and segregant strains produced higher level of isoamyl alcohol and isobutyl alcohol compared with control S. cerevisie strains of the process. Another strain, LBCM 422 native S. cerevisiae strain, sensitive to both TFL and cerulenin, a control strain for the fermentation process, produced similar levels of isoamyl alcohol in relation to both LBCM 427 and TFL and cerulenin resistant segregant strain. The results offer an important contribution for the development of a strategy for strains selection from fermentation vats of cachaça distillery, showing higher production capacity of flavouring substances..

ASSUNTO(S)

saccharomyces cerevisiae caracterizaÇÃo molecular e bioquÍmica biologia molecular caracterizaÇÃo molecular e bioquÍmica

ACESSO AO ARTIGO

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