Establishment and verification of a rapid detection method for Lacticaseibacillus paracasei based on polymerase spiral reaction (PSR): further application on screening of beer spoilage bacteria

Lacticaseibacillus paracasei is a typical food spoilage bacterium especially in beer. Due to the negative impact of L. paracasei on food preservation, a rapid detection method for L. paracasei based on polymerase spiral reaction (PSR) was established and its application was verified using different types of food samples in this study. Firstly, target digging was performed using bioinformatics techniques. A target gene pheS was selected and species-specific primers were designed. Secondly, the PSR assay was established with chromogenic reaction, which avoid false positive result due to open lid. The specificity of target and primers was tested, and the limit of detection (Kolodkin-Gal in Science 328:627–629, 2010) (5.2 × 10 4  fg/μL) was examined. Thirdly, the application of PSR assay in solid and liquid food samples were verified by artificial contamination model. The PSR assay was more efficiency in liquid food (LOD: 10 3  CFU/mL) than in solid food (LOD: 10 4  CFU/mL). Thus, L. paracasei screening in 3 types of beer (LOD: 10 3  CFU/mL) was further performed to verify to efficiency of PSR assay in screening of beer spoilage bacteria. In conclusion, pheS targeting PSR assay is useful as a rapid detection method for L. paracasei in solid and liquid food samples especially in beer.