Monitoring the growth dynamics of Tetragenococcus halophilus strains in lupine moromi fermentation using a multiplex-PCR system

Objective The microbiota of a seasoning sauce fermentation process is usually complex and includes multiple species and even various strains of one species. Moreover, composition and cell numbers of individual strains vary over the course of the entire fermentation. This study demonstrates the applicability of a multiplex PCR system to monitor growth dynamics of Tetragenococcus (T.) halophilus strains in order to evaluate their performance and help to select the most competitive starter strain. Results In a previous study we isolated T. halophilus strains from multiple lupine moromi fermentation processes and characterized them. In this study we wanted to monitor the growth dynamics of these strains in a competitive lupine moromi model fermentation process using a multiplex PCR system. Therefore, pasteurized lupine koji was inoculated with eight different T. halophilus strains, six from lupine moromi, one from an experimental buckwheat moromi fermentation process and the type strain DSM 20,339 T , to create the inoculated lupine moromi pilot scale fermentation process. With the multiplex PCR system, we could detect that all strains could grow in lupine moromi but, that TMW 2.2254 and TMW 2.2264 outperformed all other strains. Both strains dominated the fermentation after three weeks with cell counts between 4 × 10 6 to 4 × 10 7 CFU/mL for TMW 2.2254 and 1 × 10 7 to 5 × 10 7 CFU/mL for TMW 2.2264. The pH dropped to value below 5 within the first 7 days, the selection of these strains might be related to their acid tolerance.