Optimizing lipid-lowering synbiotics: strain screening, synergistic consortium formulation, prebiotic modulation, and freeze-drying process engineering for enhanced stability and efficacy.

For the development of novel synbiotic ingredients with lipid-reducing activity, this study aimed to screen lactic acid bacteria exhibiting lipid-reducing functions, formulate synbiotic compositions through strain combination, and optimize the freeze-drying process. From 80 candidate strains, Lactobacillus pentosus 9-6 and Enterococcus faecalis SMN3-2 were selected based on their high in vitro cholesterol and triglyceride degradation percentage. The results showed that co-culturing these two strains at a 2:1 proportion in combination with lactulose enhanced cholesterol and triglyceride degradation percentage to (70.7 ± 1.0)% and (58.8 ± 0.7)%, respectively. Subsequently, a Box-Behnken response surface design was applied to optimize the cryoprotectant formulation (proportion 1:6) and refine critical processing parameters including static culture for 30 min and pre-freezing at -80 °C for 12 h resulting in a synbiotic lyophilized powder with a viable bacterial count of 4.63 × 10^9 CFU/g, along with cholesterol and triglyceride degradation efficiencies of (62.6 ± 0.6)% and (53.8 ± 0.6)%, respectively. Research findings indicate that the synbiotic system formed by the combination of specific Lactobacillus strains and lactulose functions through a lipid-lowering mechanism, and the lyophilization process effectively preserves its functional efficacy. This synbiotic lyophilized powder can serve as a key functional ingredient in lipid-modulating special dietary foods, health foods, or functional dairy products, offering a potential interventional strategy for regulating lipid metabolism through functional food formulations.