Anti-Melanogenic and Skin-Protective Effects of Limosilactobacillus fermentum JNU532-Derived Fractions and Extracellular Vesicles

Excessive ultraviolet (UV) exposure induces oxidative stress and disrupts normal melanogenesis, leading to pigmentation disorders and skin damage. Probiotic-derived postbiotics, including extracellular vesicles (EVs), have recently emerged as promising bioactive agents for skin health. Therefore, this study aimed to investigate the anti-melanogenic and skin-protective effects of the cell-free supernatant (CFS), cell extract (CE), and EV-enriched fraction derived from Limosilactobacillus fermentum JNU532. In B16F10 melanocytes, both the CFS and CE significantly reduced melanin content and intracellular tyrosinase (TYR) activity in a dose-dependent manner, accompanied by downregulation of melanogenesis-related proteins (TYR, TRP-1, and TRP-2) and suppression of cyclic adenosine monophosphate signaling. In a UVB-induced hairless mouse model, topical application of the CFS and CE markedly decreased melanin accumulation, preserved epidermal structure, and prevented collagen loss. Notably, the EV-enriched fraction showed relatively stronger anti-melanogenic activity than CFS under the tested conditions, showing greater inhibition of melanin synthesis, intracellular TYR activity, and melanogenesis-related gene expression, including TYR, TRP-1, TRP-2, and MITF. Proteomic profiling revealed multiple proteins commonly identified in bacterial EVs, including membrane-associated and transporter-related proteins, supporting the vesicular characteristics of the EV-enriched fraction. These findings indicate that JNU532-derived CFS, CE, and EV-enriched fractions exhibit anti-melanogenic and skin-protective effects, with enhanced activity observed in the EV-enriched fraction under the tested conditions.