Postbiotics possess various functional activities, closely linked to their source bacterial strains and preparation methods. Therefore, the functional activities of postbiotics need to be evaluated through in vitro and in vivo methods. This study aims to prepare a postbiotic and explore its antihemolytic, anti-inflammatory, antioxidant, and antibacterial activities. Specifically, a postbiotic preparation named PostbioP-6 was prepared by intercepting 1–5 kDa of Lacticaseibacillus paracasei Postbiotic-P6 fermentation broth. The results demonstrate that PostbioP-6 exhibited notable biological activities across multiple assays. It showed significant antihemolytic activity, with a 4.9–48.1% inhibition rate at 10–50% concentrations. Anti-inflammatory effects were observed both in vitro, where 8–40% PostbioP-6 was comparable to 259.1–645.4 μg/mL diclofenac sodium, and in vivo, where 3.5 and 4.0 μL/mL PostbioP-6 significantly reduced neutrophil counts in inflamed zebrafish (p < 0.05). Antioxidant properties were evident through increased reducing power (OD₇₀₀ increased from 0.279 to 2.322 at 1.25–12.5% concentrations), DPPH radical scavenging activity (38.9–92.4% scavenging rate at 2.5–50% concentrations), and hydroxyl radical scavenging activity (4.66–10.38% scavenging rate at 0.5–4% concentrations). Additionally, PostbioP-6 demonstrated antimicrobial activity against two Gram-positive bacteria, eight Gram-negative bacteria, and one fungus. Furthermore, PostbioP-6 significantly inhibited the increase in peroxide value and malondialdehyde content in cookies, highlighting its potential application in food preservation. In conclusion, we prepared a novel postbiotic, termed PostbioP-6, which proved to have prominent anti-hemolytic, anti-inflammatory, antioxidant, and broad-spectrum antimicrobial activities. The multifunctional properties of PostbioP-6 position it as a potentially effective functional food supplement or preservative. In the future, further research is necessary to elucidate the precise mechanisms of action, identify the active components, and validate its biological activities in animal models or clinical trials.

Postbiotic is a preparation of inanimate microorganisms and/or their components that confers a health benefit on the host. Different bacterial strain and preparation method result in different functions. Herein, a postbiotic preparation named Postbiotic-P by intercepting 1-5 KD of the cell-free supernatants of L. caseiparacasei P6 fermentation broth was prepared, and its multifunctional activities were evaluated. The results showed that Postbiotic-P exerted good antihemolytic (10%-50% Postbiotic-P resulted in 4.9%-48.1% antihemolytic rate), anti-inflammatory (8% to 40% Postbiotic-P is comparable to 259.1-645.4 μg/mL of diclofenac sodium equivalents), antioxidant [reducing power (1.25%-12.5% Postbiotic-P resulted in the increase of OD700 from 0.279-2.322), DPPH free radical scavenging activity (2.5%-50% Postbiotic-P resulted in 38.9%-92.4% free radical scavenging rate), and hydroxyl radical scavenging activity (0.5%-4% Postbiotic-P resulted in 4.66%-10.38% hydroxyl radical scavenging rate)], and antimicrobial activities (against 2 Gram-positive, 8 Gram-negative and 1 fungus). Furthermore, it was proved that Postbiotic-P could significantly inhibit the increase of the peroxide value and the malondialdehyde content in cookies, indicating the application potential of Postbiotic-P in food preservation. Taken together, Postbiotic-P has good application potential for the development of health care products and functional foods. However, further studies are needed to determine their precise mechanism of action, to clarify the active components responsible for the function, and to validate the biological activities in animal models or clinical trials.