Development and Application of a Multiplex Real-Time Fluorescent PCR Assay for the Detection of Common Lactobacillus Species in Food

Lactobacillus species are widely used in various food products, including conventional food products, dairy products, and health food products. To achieve the desired functional properties, manufacturers commonly incorporate two or more distinct Lactobacillus species during production. In this study, a multiplex PCR detection method was developed for four Lactobacillus species commonly used in food based on TaqMan real-time fluorescent PCR technology, enabling the efficient and rapid identification of multiple Lactobacillus strains in food matrices. The research team selected and validated four representative species—Lactobacillus rhamnosus, Lactobacillus plantarum, Lactobacillus acidophilus, and Lactobacillus paracasei—as targets for the multiplex PCR assay, designing specific primer–probe combinations for each. The accuracy and reliability of the detection method were rigorously evaluated through a series of validation experiments, including the assessment of primer–probe specificity, optimization of fluorescent signal labeling chemistries, determination of the limits of detection for individual strains, evaluation of the method’s repeatability, and analysis of commercial food samples. The results demonstrated that the selected primer–probe sets exhibited no cross-reactivity in the multiplex system and specifically amplified their target Lactobacillus species, with no amplification observed for non-target strains. The established method achieved a minimum LOD for L. acidophilus of 10² CFU/g and showed high repeatability across replicates. Furthermore, the successful detection of labeled Lactobacillus strains in commercial products confirmed the method’s practical applicability. Therefore, the developed multiplex real-time PCR assay provides a reliable, sensitive, and high-throughput tool for the simultaneous detection of multiple Lactobacillus species in complex food products and holds potential for application in quality control, product authentication, and regulatory compliance monitoring.