Sourdough fermentation is a cereal fermentation that is characterized by the formation of stable yeast/lactic acid bacteria (LAB) associations. It is a unique process among food fermentations in that the LAB that mostly dominate these fermentations are heterofermentative. In the present study, four wheat sourdough fermentations were carried out under different conditions of temperature and backslopping time to determine their effect on the composition of the microbiota of the final sourdoughs. A substantial effect of temperature was observed. A fermentation with 10 backsloppings (once every 24 h) at 23°C resulted in a microbiota composed of Leuconostoc citreum as the dominant species, whereas fermentations at 30 and 37°C with backslopping every 24 h resulted in ecosystems dominated by Lactobacillus fermentum. Longer backslopping times (every 48 h at 30°C) resulted in a combination of Lactobacillus fermentum and Lactobacillus plantarum. Residual maltose remained present in all fermentations, except those with longer backslopping times, and ornithine was found in almost all fermentations, indicating enhanced sourdough-typical LAB activity. The sourdough-typical species Lactobacillus sanfranciscensis was not found. Finally, a nonflour origin for this species was hypothesized.Sourdough is a mixture of ground cereals and water that ferments spontaneously. Sourdoughs improve the properties of the bread dough, enhance bread texture and flavor, and delay bread spoilage and staling (11,26,40). Many studies have investigated the composition of the sourdough microbiota of traditional type I sourdoughs, which are daily backslopped, with both culture-dependent and culture-independent techniques (9-11). Lactic acid bacteria (LAB) and yeasts play a key role in the sourdough fermentation process (9,22,25). Unlike most other well-known food fermentation processes, sourdough is usually dominated by heterofermentative LAB, commonly belonging to the genus Lactobacillus (4, 9).Despite changes in raw materials or the bakery environment, sourdoughs are stable ecosystems (43,58). This stability can be ascribed to specific metabolic adaptations to the sourdough ecosystem or the production of antimicrobial compounds (10, 18). Carbohydrate fermentation targeted toward maltose catabolism (encompassing maltose phosphorylase activity), the use of alternative external electron acceptors (such as fructose), and/or the expression of the arginine deiminase (ADI) pathway are metabolic activities that favor energy production, cofactor (re)cycling, and/or tolerance toward acid stress (4,10,11,18,19,23). Moreover, certain LAB species form a stable association with certain yeast species, due to dedicated nutritional, trophic, and metabolic interactions (4, 9, 10, 18, 23). Consequently, some LAB species that participate in sourdough fermentations are considered typical inhabitants of the sourdough ecosystem, among which Lactobacillus plantarum, Lactobacillus fermentum, Lactobacillus paralimentarius, Lactobacillus brevis, and Lactobacillus sanfrancisce...