Metabolismo de lactose em Kluyveromyces marxianus UFV-3 e Kluyveromyces lactis JA6 / Metabolism of lactose by Kluyveromyces marxianus UFV-3 and Kluyveromyces lactis JA6




The fermentative metabolism of lactose in Kluyveromyces marxianus UFV-3 was compared to the Kluyveromyces lactis JA6 under aerobic and hypoxia through the analysis of kinetics of growth, consumption of substrate, production of ethanol and formation of biomass, depending on the concentration of lactose. It was determinated the gene expression and activity of key enzymes of metabolism of lactose under aerobic and hypoxia. In fermentations carried out under aerobic and hypoxia in lactose concentrations of 0.25 to 64 mM, K. marxianus UFV-3 showed higher specific growth rate and higher concentration of biomass after 24 hours of cultivation, for K. lactis JA6. In fermentations with 64 mM lactose under aerobic and hypoxia K. marxianus UFV-3 showed higher yield to ethanol by K. lactis JA6, demonstrating that high concentrations of substrate metabolism favors fermentation in K. marxianus UFV-3. Under aerobic K. marxianus UFV-3 has more activity of pyruvate dehydrogenase that K. lactis JA6, justifying the formation of higher biomass and higher growth rate observed in K. marxianus UFV-3. Under hypoxia the highest activities of pyruvate decarboxylase and β- galactosidase of K. marxianus UFV-3 in relation to K. lactis JA6 seem to be the factors that contribute to the increased formation of ethanol in K. marxianus UFV-3 when compared to K. lactis JA6. In hypoxia K. marxianus showed higher expression of genes that encode enzymes β-galactosidase, pyruvate decarboxylase and the Leilor pathway for when compared to aerobic. Indicating that these genes are important for the metabolism of lactose in hypoxia. Already in K. lactis JA6 none of these genes showed increased expression in hypoxia. It appears the higher expression of genes encoding key enzymes of metabolism of lactose as the major enzymatic activity is responsible for fermentation potential of K. marxianus UFV-3.


metabolism lactose metabolismo kluyveromyces kluyveromyces biologia e fisiologia dos microorganismos lactose

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