Saccharomyces cerevisiae is one of the best investigated organisms. However, its volatile space has so far only found little attention in yeast literature. In this thesis the yeast metabolic model has been updated by the volatile space, also the on-line methods SESI-Orbitrap and MCC-IMS have been used to investigate the off-gas of yeast fermentations. In addition, a cDNA microarray has been performed on fermentations in minimal- and industrial molasses medium.