Sourdough is the foremost cereal fermentation performed in a variety of technologies with almost any cereal. The lactobacilli studied most intensely include Lactobacillus sanfranciscensis, L. reuteri and L. pontis isolated from traditional and modern rye and wheat fermentations. Molecular biology tools are available for their rapid identification and monitoring throughout a process. The currently available insight on their metabolism can be used to explain their prevalence in this environment and their interactions. Key genes of the sugar degradation pathway were cloned and characterised from L. sanfranciscensis. In addition some strains were found to have special properties including the production of antagonistic compounds or the adhesion to human intestinal cells.