Carbon Source–Dependent Metabolic Shift of Lactobacillus gasseri Reveals Condition‐Specific Bioactive Metabolites for Postbiotic Applications

Lactobacillus gasseri is a probiotic bacterium with diverse health‐promoting properties; however, how carbon source availability shapes its metabolite composition relevant to postbiotic applications remains insufficiently understood. In this study, we investigated carbon source–dependent metabolic shifts in an industrial L . gasseri strain CBT LGA1 by profiling intracellular metabolites using gas chromatography–mass spectrometry in cells cultured with glucose, galactose, or cellobiose as the sole carbon source. A total of 91 intracellular metabolites were identified, of which 64 were significantly altered across carbon sources (FDR‐adjusted q < 0.05). Principal component analysis (PCA) explained 58.7% of the total variance ( R 2 X = 0.5871), with PC1 separating glucose and cellobiose conditions and PC2 distinguishing galactose. Glucose promoted the accumulation of pyruvate, a key central carbon metabolite, and lactate, a fermentation product, whereas galactose induced galactose‐derived sugars and oxidative carbohydrate metabolites associated with the pentose phosphate pathway, accompanied by increased fatty acids and dipeptides. Cellobiose caused a marked accumulation of the upper glycolytic intermediates and nucleotides and exhibited the highest diversity of bioactive metabolites. Collectively, these findings demonstrate that carbon source selection critically modulates the intracellular metabolic landscape of L. gasseri and provide a metabolic basis for the rational design and optimization of condition‐specific postbiotic production strategies.