Aims: To assess the structure and stability of a dominant lactic acid bacteria (LAB) population during the propagation of rye sourdough in an industrial semi-fluid production over a period of 7 months. Methods and Results: The sourdough was started from a 6-year-old freezedried sourdough originating from the same bakery. A unique microbial consortium consisting mainly of bacteria belonging to species Lactobacillus helveticus, Lactobacillus panis and Lactobacillus pontis was identified based on culture-dependent (Rep-PCR) and culture-independent [denaturing gradient gel electrophoresis (DGGE)] methods. Three of the isolated Lact. helveticus strains showed remarkable adaptation to the sourdough conditions. They differed from the type strain by the ability to ferment compounds specific to plant material, like salicin, cellobiose and sucrose, but did not ferment lactose. Conclusion: We showed remarkable stability of a LAB consortium in rye sourdough started from lyophilized sourdough and propagated in a large bakery for 7 months. Lactobacillus helveticus was detected as the dominant species in the consortium and was shown to be metabolically adapted to the sourdough environment. Significance and Impact of the study: The use of an established and adapted microbial consortium as a starter is a good alternative to commercial starter strains.