Efficient maltotriose fermentation through hydrolysis mediated by the intracellular invertase of Saccharomyces cerevisiae

Background It is well known that in the yeast S. cerevisiae the sugars sucrose and maltose/maltotriose are metabolized by different pathways: sucrose is hydrolyzed by extracellular invertase (encoded by SUC genes), while maltose and maltotriose are actively transported into the cell and hydrolyzed by intracellular a-glucosidases (both proteins encoded by the MAL genes). Nevertheless, several reports have shown that some SUC genes can be located proximal to MAL genes at the telomeres of different chromosomes. Furthermore, the SUC genes also allow the synthesis of an intracellular form of invertase, an enzyme with no obvious function in yeasts [1]. We have already shown that sucrose can be metabolized by yeast cells through MAL-encoded transporters and a-glucosidases.