Effects of the carbon source on the physiology and invertase activity of the yeast Saccharomyces cerevisiae FT858.

Saccharomyces cerevisiae FT858 is an industrial yeast strain with high fermentative efficiency, but marginally studied so far. The aim of this work was to evaluate the biotechnological potential of S. cerevisiae FT858 through kinetic growth parameters, and the influence of the concentration of the substrate on the synthesis of the invertase enzyme. Invertases have a high biotechnological potential and their production through yeast is strongly influenced by the sugars in the medium. S. cerevisiae FT858 has an excellent biotechnological potential compared to the industrial yeast reference S. cerevisiae CAT-1, as it presented a low glycerol yield on the substrate (Y GLY/S) and a 10% increase in ethanol yield on sucrose in cultures with sucrose at 37 °C. The substrate concentration directly interfered in invertase production and the enzymatic expression underwent strong regulation through glucose concentration in the culture medium and S. cerevisiae CAT-1 presented constitutive behavior for the invertase enzyme.

Effects of the carbon source and the interaction between carbon sources on the physiology of the industrial Saccharomyces cerevisiae CAT-1.

During industrial fermentation, wild isolates are able to persist and even predominate in the bioreactors. Saccharomyces cerevisiae CAT-1 was one of these isolates and now is one of the yeasts mostly used in industrial ethanol processes in Brazil due to its efficient fermentation capacity. Despite it, the strain's physiology has been marginally studied so far. Since strains of the same species may have different responses to a specific cultivation condition, this work aimed to evaluate the physiology of S. cerevisiae CAT-1 in batch cultures using different carbon sources (glucose, fructose, sucrose, maltose, and galactose) as a sole carbon source and in binary mixtures, at 30 and 37 °C. The results showed that the fructose, sucrose, and maltose were the sugars that presented the highest ethanol yields on the substrate (0.40 gethanol gsubstrate-1) at both temperatures. Galactose was the sugar that the yeast had the lowest affinity given the lowest maximum specific growth rate (0.28 h-1). Despite the influence of a variety of mechanisms for sugar transport, the cells consume first substrates with fewer metabolic steps to catabolism and are susceptible to adaptive evolution depending on the availability of substrate.