In Vitro Skin-Protective Effects of Sumyong Nature, a Kimchi- and Soybean-Derived Fusion-Fermented Microbial Supernatant, in Human Keratinocytes: Involvement of MAPK-Related Signaling.

Sumyong Nature (SN) is a kimchi- and soybean-derived fusion-fermented microbial supernatant prepared from Lactobacillus acidophilus, Saccharomyces cerevisiae, Weissella cibaria, and Bifidobacterium longum. This study examined the in vitro effects of SN on UVB-induced damage and skin-related cellular responses in human keratinocytes. Cell viability assays, gene expression analysis, luciferase reporter assays, immunoblotting, scratch wound-healing assays, and LC-Q-TOF-MS analysis were conducted. SN showed no significant cytotoxicity in HaCaT or HEK293T cells at concentrations up to 75 μg/mL. In UVB-irradiated HaCaT cells, SN improved cell viability, suppressed MMP-1 expression, increased HAS-1 expression, and modulated UVB-responsive stress-related markers, including SOD-1, Nrf2, and HO-1. SN also promoted wound closure in keratinocytes and was associated with changes in NF-κB-, AP-1-, CREB-, and MAPK-related signaling responses under the tested conditions. LC-Q-TOF-MS analysis tentatively identified several candidate constituents, including pectolinarin and aloeresin-related compounds. Collectively, these findings suggest that SN exerts multiple beneficial in vitro effects in keratinocyte-based assays, warranting further mechanistic investigation and validation in advanced experimental models.