Supplementary materials for "The key quorum sensing gene luxS in Lactobacillus acidophilus CICC6074 and Lactobacillus helveticus R0052 mediates organic acid production and promotes protein hydrolysis in yogurt"

In this study, the effect of luxS, a key gene for QS, on the characteristic flavor of yogurt and its molecular mechanism in the co-fermentation of yogurt with Lactobacillus acidophilus CICC6074 and Lactobacillus helveticus R0052 engineered probiotics was investigated. Using the pMG36e plasmid as a vector and employing gene editing technology, we have initially constructed the luxS gene overexpression strains L. acidophilus CICC6074-pMG36e-luxS and L. helveticus R0052-pMG36e-luxS. Their effects on yogurt quality, including pH, titratable acidity, viable bacterial count, texture, water-holding capacity, and protein hydrolysis, were further explored. In addition, HS-SPME-GC-MS and UHPLC-MS, combined with metabolomics, were used to elucidate its effects and molecular mechanisms on the production of volatile and non-volatile flavor substances. By enhancing AI-2 signal transmission, we improved the flavor of yogurt, increased the survival rate and metabolic efficiency of probiotics, thereby enhancing the overall quality and functionality of the yogurt. This study provides a theoretical foundation and technical support for manipulating the LuxS/AI-2 system in yogurt production and probiotic engineering, offering a new approach for developing probiotic strains with enhanced health benefits, and holds broad application prospects.