Upcycling of Adlay Bran via <i>Lactobacillus</i> Fermentation Enhances Anti-Melanogenic and Antioxidant Activities through MITF/Tyrosinase Pathway Modulation

Upcycling agricultural byproducts into high-value functional ingredients represents a sustainable strategy for environmental preservation. Adlay (<i>Coix lacryma-jobi</i> var. <i>ma-yuen</i>) bran, a nutrient-rich byproduct discarded during seed polishing, was fermented with <i>Lactiplantibacillus plantarum</i>, which markedly enhanced its anti-melanogenic activity. The fermented extract suppressed melanin production by modulating the MITF/tyrosinase signaling pathway, with the n-butanol (BuOH) fraction exhibiting the most potent effect. Isoquercitrin and 2-O-β-glucopyranosyl-7-methoxy-2H-1,4-benzoxazin-3(4H)-one were identified as the principal active compounds, and <i>in silico</i> analysis revealed strong binding affinities to tyrosinase. Furthermore, fermentation enhanced antioxidant capacity, as evidenced by DPPH and FRAP assays. Collectively, these findings demonstrate that fermented adlay bran constitutes a sustainable bioactive resource with promising applications in skincare and nutraceuticals.