Metabolic interactions between Lactococcus lactis and commercial starter cultures enhances the quality and flavor of fermented milk

Abstract

This research investigated the metabolic interactions between Lactococcus lactis strains and commercial starter cultures during fermentation. Through integrated analysis of fermentation characteristics, we demonstrated that L. lactis supplementation significantly enhanced both viable bacterial counts and fermentation kinetics. The metabolomic profiling showed that the commercial starter cultures and L. lactis NGD8 co-fermentation group (CSL + NGD8) developed distinctive “complex fruit-dairy” flavor characteristics, with significantly elevated levels of bioactive metabolites, including 6-hydroxycaproic acid, hippuric acid and methylmalonic acid. Furthermore, genome-scale metabolic models (GEMs) elucidated the directional metabolite transfer mechanisms, where commercial starter cultures functioned as metabolite donors, facilitating the directed transfer of amino acids (glycine, glutamic acid, and alanine) and their precursors to L. lactis NGD8 during fermentation. This metabolic interaction was further validated by significant variations in free amino acid profiles. These findings provide novel insights into the synergistic effects of starter culture combinations and develop improved starter cultures with unique Chinese characteristics through precise regulation of strain interactions.