RESUMO
Saccharomyces cerevisiae normally cannot assimilate mannitol, a promising brown macroalgal carbon source for bioethanol production. The molecular basis of this inability remains unknown. We found that cells capable of assimilating mannitol arose spontaneously from wild-type S. cerevisiae during prolonged culture in mannitol-containing medium. Based on microarray data, complementation analysis, and cell growth data, we demonstrated that acquisition of mannitol-assimilating ability was due to spontaneous mutations in the genes encoding Tup1 or Cyc8, which constitute a general corepressor complex that regulates many kinds of genes. We also showed that an S. cerevisiae strain carrying a mutant allele of CYC8 exhibited superior salt tolerance relative to other ethanologenic microorganisms; this characteristic would be highly beneficial for the production of bioethanol from marine biomass. Thus, we succeeded in conferring the ability to assimilate mannitol on S. cerevisiae through dysfunction of Tup1-Cyc8, facilitating production of ethanol from mannitol.
Assuntos
Proteínas Correpressoras/metabolismo , Regulação Fúngica da Expressão Gênica , Manitol/metabolismo , Proteínas Nucleares/metabolismo , Proteínas Repressoras/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Proteínas Correpressoras/genética , DNA Fúngico/química , DNA Fúngico/genética , Perfilação da Expressão Gênica , Teste de Complementação Genética , Análise em Microsséries , Dados de Sequência Molecular , Mutação , Proteínas Nucleares/genética , Proteínas Repressoras/genética , Saccharomyces cerevisiae/crescimento & desenvolvimento , Proteínas de Saccharomyces cerevisiae/genética , Análise de Sequência de DNARESUMO
Mannitol is a promising marine macroalgal carbon source. However, organisms that produce ethanol from mannitol are limited; to date, only the yeast Pichia angophorae and the bacterium Escherichia coli KO11 have been reported to possess this capacity. In this study, we searched a yeast strain with a high capacity to produce ethanol from mannitol and selected Saccharomyces paradoxus NBRC 0259 for its ability to produce ethanol from mannitol. This ability was enhanced after a 3-day cultivation of this strain in medium containing mannitol; the enhanced strain was renamed S. paradoxus NBRC 0259-3. We compared the ability of strain NBRC 0259-3 to produce ethanol from mannitol and glucose, under several conditions, with those of P. angophorae and E. coli KO11. As a result, we concluded that S. paradoxus NBRC 0259-3 strain is the most suitable yeast strain for the production of ethanol from mannitol.
