Improvement of maltotriose fermentation by Saccharomyces cerevisiae

AIMS: To enhance the fermentation of maltotriose by industrial Saccharomyces cerevisiae strains. METHODS AND RESULTS: The capability to ferment maltotriose by an industrial yeast strain that uses this sugar aerobically was tested in shake flasks containing rich medium. While the presence of maltose in the medium did not improve maltotriose fermentation, enhanced and constitutive expression of the AGT1 permease not only increased the uptake of maltotriose, but allowed efficient maltotriose fermentation by this strain. Supplementation of the growth medium with 20 mmol magnesium l(-1) also increased maltotriose fermentation. CONCLUSIONS: Over expression of the AGT1 permease and magnesium supplementation improved maltotriose fermentation by an industrial yeast strain that respired but did not ferment this sugar. SIGNIFICANCE AND IMPACT OF THE STUDY: This work contributes to the elucidation of the roles of the AGT1 permease and nutrients in the fermentation of all sugars present in starch hydrolysates, a highly desirable trait for several industrial yeasts.