Discovery of Multifunctional Probiotic Strains with Antioxidant, Anti-Inflammatory, Antimicrobial, and Skin Barrier-Supportive Activities for Postbiotic Cosmetic Applications

Probiotic strains with multifunctional skin-beneficial properties represent promising candidates for next-generation cosmetic ingredients. In this study, a systematic stepwise screening strategy was applied to an in-house bacterial library comprising 302 isolates to identify candidates with antioxidant, anti-inflammatory, antimicrobial, wound-healing, and skin barrier-supportive activities. From this library, 33 strains were selected based on preliminary assessments and subjected to comprehensive in vitro evaluation. Cell viability and cytotoxicity assays confirmed the safety of all selected strains in RAW264.7 macrophages and HaCaT keratinocytes. Several strains exhibited strong DPPH radical scavenging activity and significantly inhibited nitric oxide production in LPS-stimulated macrophages. Among the selected candidates, Lacticaseibacillus rhamnosus DM073 demonstrated the most potent anti-inflammatory activity, whereas Lactiplantibacillus plantarum DM043 exhibited the greatest wound-healing capacity. All five selected strains displayed antimicrobial activity against Cutibacterium acnes. Furthermore, selected strains, particularly Lactiplantibacillus plantarum DM175 and Ligilactobacillus salivarius DM079, enhanced the expression of skin barrier-related genes, including zonula occludens-1 (ZO-1), occludin (OCLN), claudin-1 (Cla-1), and filaggrin (FLG), and partially restored their expression under TNF-α/IFN-γ-induced inflammatory conditions. Selected strains also reduced the expression of inflammatory chemokines in stimulated keratinocytes. Collectively, these findings demonstrate that the selected probiotic strains possess complementary multifunctional activities associated with skin health. In particular, DM073 exhibited superior anti-inflammatory activity, DM043 showed strong wound-healing potential, and DM175 demonstrated remarkable skin barrier-supportive effects. These strain-specific properties support their potential application in the development of probiotic-derived postbiotic cosmetic ingredients for skin soothing, barrier reinforcement, skin recovery, and microbiome-friendly skincare formulations. Further studies are warranted to evaluate their efficacy and safety in advanced skin models and clinical cosmetic applications.