Functional Properties, Metabolic Profile and Safety Attributes of Postbiotics from Lacticaseibacillus acidophilus and Lactiplantibacillus plantarum

• The postbiotics derived from two probiotic strains demonstrated strain specific functional and biological strengths. • Synergistic antibacterial potency was observed in the postbiotic cocktails that was prepared by mixing the two postbiotics in equal volumes. • Both the postbiotics showed dose-dependent inhibition of protein denaturation and hemolysis confirming their strong anti-inflammatory effects. • The safety of the postbiotics was validated by their hemocompatibility and lack of cytotoxicity in epithelial and fibroblast cell lines. Postbiotics are emerging as promising next-generation probiotics owing to their stability, safety, and multifaceted health benefits. In the present study, the postbiotics from Lactobacillus acidophilus BLAC 258 ( LA ) and Lactiplantibacillus plantarum BLP 272 ( LbP ) were analyzed for their antibacterial, antioxidant, anti-inflammatory, other biochemical and safety attributes. The postbiotic fractions (PF) of LA demonstrated potent antagonistic actions against Shigella dysenteriae and Escherichia coli , whereas, PF from LbP were more effective against Bacillus cereus . The combination of the two postbiotics resulted in synergistic antibacterial effects with MIC values of 6.25 mg / ml for Sh. dysenteriae and 12.5 mg / ml for B. cereus and E. coli. The LA postbiotics demonstrated superior antioxidant capacity (58.73 %), TPC (2515 ± 1.41 mg GAE / L), and TFC (1432.25 ± 1.450 mg Qu/100 g). On the contrary, LbP post-biotics contained higher total protein (338 µg/g) compared to LA (226 µg/g) ( p < 0.05). A dose-dependent anti-inflammatory response was observed for both postbiotics by inhibiting albumin denaturation and heat-induced hemolysis. During metabolic profiling, 16 major constituents were observed in the two postbiotics with strain-specific variations, while their total short-chain fatty acid levels were comparable. Treatment with proteolytic enzymes diminished antibacterial effects only in LbP post-biotics. Both PFs tested PF showed no hemolysis of human, sheep, and rabbit red blood cell (RBC), or cytotoxicity on porcine epithelial (IPEG-J2) and normal (MRC5) cell lines, confirming their safety. These findings highlight the potential of LA and LbP postbiotics as safe and effective bioactive agents with significant antibacterial, antioxidant, and anti-inflammatory potential.