The disclosure relates to the use of a mutant SSK1 gene encoding a truncated ssk1 protein for the construction of a mutant yeast strain with decreased glycerol production, when compared to the wild-type strain. It relates further to the use of such strains for high-yield bioethanol production, especially in high osmotic media, or on cellulosic hydrolysates, where normal yeast strains do produce a significant amount of glycerol.