Maltose and Maltotriose Transporters in Brewer’s Saccharomyces Yeasts: Polymorphic and Key Residues in Their Activity

Maltose and maltotriose are the most abundant sugars in brewing wort, and their transport represent a critical bottleneck in the fermentation process. This transport relies on specific transmembrane proteins; however, many yeast strains exhibit inefficient uptake of these sugars, particularly maltotriose. Addressing this limitation requires a comprehensive understanding of the factors influencing the transport of maltose and maltotriose. This review provides a detailed synthesis of the key characteristics and functions of the maltose and maltotriose transmembrane transporters identified in brewer's <i>Saccharomyces</i> yeasts. Critical amino acid residues involved in transporter activity are also highlighted, and the impact of specific polymorphisms and sequence variations on sugar preference and uptake efficiency is examined. Furthermore, a thorough discussion of the most important reported residues is presented, underscoring the need to closely examine their amino acid composition to better understand transporter mechanisms, optimize their performance, and enhance fermentation outcomes.