Taxonomic Structure and Monitoring of the Dominant Population of Lactic Acid Bacteria during Wheat Flour Sourdough Type I Propagation Using Lactobacillus sanfranciscensis Starters
ABSTRACTThe structure and stability of the dominant lactic acid bacterium population were assessed during wheat flour sourdough type I propagation by using singly nine strains ofLactobacillus sanfranciscensis. Under back-slopping propagation with wheat flour type 0 F114, cell numbers of presumptive lactic acid bacteria varied slightly between and within starters. As determined by randomly amplified polymorphic DNA-PCR and restriction endonuclease analysis-pulsed-field gel electrophoresis analyses, only three (LS8, LS14, and LS44) starters dominated throughout 10 days of propagation. The others progressively decreased to less than 3 log CFU g−1. Partial sequence analysis of the 16S rRNA andrecAgenes and PCR-denaturating gradient gel electrophoresis analysis using therpoBgene allowed identification ofWeissella confusa,Lactobacillus sanfranciscensis,Lactobacillus plantarum,Lactobacillus rossiae,Lactobacillus brevis,Lactococcus lactissubsp.lactis,Pediococcus pentosaceus, andLactobacillusspp. as the dominant species of the raw wheat flour. At the end of propagation, one autochthonous strain ofL. sanfranciscensiswas found in all the sourdoughs. Except forL. brevis, strains of the above species were variously found in the mature sourdoughs. Persistent starters were found in association with other biotypes ofL. sanfranciscensisand withW. confusaorL. plantarum. Sourdoughs were characterized for acidification, quotient of fermentation, free amino acids, and community-level catabolic profiles by USING Biolog 96-well Eco microplates. In particular, catabolic profiles of sourdoughs containing persistent starters behaved similarly and were clearly differentiated from the others. The three persistent starters were further used for the production of sourdoughs and propagated by using another wheat flour whose lactic acid bacterium population in part differed from the previous one. Also, in this case all three starter strains persisted during propagation.