Enhancing lactic acid tolerance in Fructilactobacillus sanfranciscensis via adaptive evolution for sourdough fermentation applications.

Fructilactobacillus sanfranciscensis is extensively used in the food industry, notably for sourdough fermentation; however, its mass production is hindered by growth inhibition due to lactic acid accumulation in the medium. This study aimed to enhance the acid tolerance of F. sanfranciscensis SPC-SNU 70-4 via adaptive laboratory evolution (ALE) to improve its viability as an industrial sourdough starter. The ALE process involved sequential cultivation under progressively acidic conditions. As a result, the strain had significantly improved growth rates that were 1.4- and 1.2-fold higher than those of the parental strain at pH 6.5 and 4.1, respectively. Comparative analyses of the fermentation and metabolite profiles using GC/TOF-MS and SPME-GC/MS revealed that the evolved strain not only retained but, in some cases, enhanced the production of key metabolites essential for the flavor of bread. Sensory evaluation confirmed that the sourdough bread produced with the evolved strain maintained desirable sensory attributes comparable to those produced by the parental strain. These findings highlight the potential of the evolved F. sanfranciscensis as a robust starter culture in the food industry, particularly its enhanced tolerance to acidic environments without any compromise to the sensory quality of the resulting sourdough products.