A Species-Specific qPCR Method for Enumeration of Lactobacillus sanfranciscensis, Lactobacillus brevis, and Lactobacillus curvatus During Cocultivation in Sourdough

Lactobacillus sanfranciscensis , Lactobacillus brevis , and Lactobacillus curvatus are frequently isolated from cereal-based fermented foods and are the dominant lactic acid bacteria in Korean sourdough. Detection of the individual species and their enumeration during fermentation are of great importance for maintaining the quality of bakery products. Here, we developed a species-specific quantitative polymerase chain reaction (qPCR) method to monitor the population of these three bacterial species during cocultivation in sourdough. Target genes, including those encoding nucleoside hydrolase, hypothetical protein, and glyoxalase, were selected by MegaBLAST for the detection of L. sanfranciscensis , L. brevis , and L. curvatus , respectively. The specificities of PCR primer sets were verified with qPCR; constant cycle threshold (Ct) values were obtained from mixed genomic DNAs (gDNAs) of target and non-target strains. The qPCR results were unaffected by the sourdough matrix. The cell numbers derived from qPCR were 10–65% higher than those obtained using a conventional plate-counting method. The qPCR standard curves for the three Lactobacillus species were established, and their populations were successfully enumerated during sourdough propagation. This method would enable quantification of three Lactobacillus species during cocultivation in sourdough and provide useful information on microbial commensalism that is essential to obtain high-quality bread.