Skin Health Function of Distilled Soju Byproduct Fermented with <i>Saccharomyces cerevisiae</i> MGE 3400

The skin serves as a vital barrier against environmental and biological stressors, and its impairment leads to premature aging and various dermatological disorders. The growing demand for natural, sustainable cosmetic ingredients has drawn attention to food industry byproducts as potential bioactive sources. Production of distilled soju generates substantial byproducts that are typically discarded but possess valuable metabolites. This study investigated the skin health-related functions of distilled soju byproducts fermented with the <i>Saccharomyces cerevisiae</i> MGE 3400 as a starter culture, which was isolated from a nuruk, compared with a commercial yeast. In vitro assays were performed to evaluate antioxidant activity and antimicrobial activity against the skin pathogens <i>Candida albicans, Staphylococcus aureus</i>, and <i>Cutibacterium acnes</i>, as well as moisturizing-related HAS2 expression, UV-protective effects, and wound-healing properties using the HaCaT cell line. <i>S. cerevisiae</i> MGE 3400 fermented distilled soju byproduct showed stronger antioxidant and antimicrobial activities than the control. In addition, they promoted the expression of hyaluronan synthase 2 (HAS2) and insulin-like growth factor 1 (IGF-1) genes, enhanced ultraviolet (UV) damage protection, and accelerated wound closure in keratinocyte HaCaT cells, suggesting an overall improvement in skin-regenerative potential. These findings suggest that <i>S. cerevisiae</i> MGE 3400 can enhance the functional properties of distilled soju byproduct, supporting their use as a sustainable source of natural ingredients for cosmetic and dermatological applications.