Efficient utilization of compound oligosaccharides by Lactobacillus paracasei ProSci-92 and their application in fermented milk

Prebiotics promote the proliferation and colonization of probiotics in the intestine; therefore, synergistic application of probiotics and functional oligosaccharides can confer significant health benefits to the host. This study optimized a complex prebiotic combination that enhanced the growth of Lactobacillus paracasei ProSci-92 by measuring the optical density at 600 nm, pH, and viable cell counts. Through response surface optimization, the optimal ratio was determined to be 1.959% trehalose, 1.029% inulin, and 1.582% fructooligosaccharides. Under these conditions, cell density reached 1.629 ± 0.012, and the viable cell count was (6.5 ± 0.28) × 10 9 cfu/mL, representing increases of 12.3% and 1.67-fold, respectively, compared with the de Man, Rogosa, and Sharpe agar medium control group. The optimized compound was subsequently applied to fermented milk; its rheological properties, texture characteristics, and viable bacterial counts were analyzed using sucrose as the control. The results show that the compound group coagulated 1 h earlier than did the sucrose control, and exhibited higher elasticity and viscosity coefficients. During the 28-d storage period, the pH decreased gradually (final value: 4.16), titratable acidity remained low (final value: 102°T [degrees of titratable acidity]), viable bacterial count remained above 10 8 cfu/mL, and water-holding capacity averaged 65.86%. Moreover, both textural attributes and sensory evaluation scores improved significantly. Metabolomic analysis identified 87 differential metabolites between the PC92-Oli (experimental) group and the PC92-Suc (control) group, which were primarily associated with the ABC transport system, AA biosynthesis, and carbon metabolism pathways. The compound oligosaccharide mixture activated specific metabolic pathways in the strain, promoted the synthesis of functional metabolites, inhibited fatty acid production, and accelerated extracellular polysaccharide synthesis. These findings provide a strong scientific basis for enhancing the product development and functional properties of probiotic fermented milk, and offer innovative perspectives and strategies for improving its production and storage characteristics.