Regulatory Effect of Sea Rice Bio-Fermentation Product on the Melanin Synthesis Pathway

Abstract

Sea rice harbors a diverse array of bioactive constituents, among which the efficient liberation of phytic acid is pivotal for unlocking its full functional potential. In this study, a co-fermentation system integrating yeast and lactic acid bacteria was established to generate a sea rice fermentation filtrate (SRF) with enhanced phytic acid (PA) content, aiming to broaden its application as a cosmeceutical ingredient and to facilitate the high-value utilization of sea rice. Response surface methodology was employed to optimize the inoculation ratios of the two microbial strains and the fermentation duration, and the PA levels were quantified using a commercial assay kit. The anti-melanogenic activity of SRF was assessed in murine B16 melanoma cells, and the underlying molecular mechanisms were elucidated with particular emphasis on the PI3K/AKT/GSK3β/MITF signaling cascade. Under the optimal conditions, specifically Saccharomyces cerevisiae (SC) inoculation at 4.5% and Lactobacillus plantarum (LP) at 6.0% with a fermentation time of 18 h, the PA concentration reached 576.61 μg/mL. Mechanistically, SRF treatment enhanced GSK3β phosphorylation, which was associated with reduced MITF phosphorylation and diminished the expression of downstream melanogenic enzymes, thereby effectively curtailing melanin synthesis, suggesting that SRF, as a complex fermentation product containing multiple bioactive constituents including PA, exhibits potent whitening efficacy. Collectively, these results provide novel perspectives for the valorization of sea rice and the development of natural skin-lightening agents, while also contributing to the extension of the sea rice industrial value chain.