Evaluation of the skin whitening efficiency of Staphylococcus epidermidis fermentation broth and its oligopeptides

In this work, two types of Staphylococcus epidermidis fermentation broth were prepared in beef-protein medium and beef-protein medium with glucose, named as SFB and Glu-SFB. As a positive control, 0.5 mg/mL kojic acid was utilized, which led to a 33.1 ± 1.32 % drop in melanin content and a 30.9 ± 2.95 % reduction in tyrosinase activity in B16-F10 cells. After treatment with SFB and Glu-SFB, the intracellular melanin content diminished by 35.4 ± 0.67 % and 48.5 ± 1.36 %, while tyrosinase activity declined by 59.1 ± 1.49 % and 64.4 ± 2.03 %, respectively. The two S. epidermidis fermentation broth markedly diminish intracellular melanin concentrations and tyrosinase activity, leading to a whitening effect. The whitening efficacy of Glu-SFB surpasses that of SFB and exceeds that of 0.5 mg/mL kojic acid. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) combined with untargeted metabolomics analysis was utilized to identify differential metabolites. Six oligopeptides were identified as Trp-Phe-Tyr-Leu (WFYL), Gln-Ile-Gly-Pro (QIGP), Val-Arg-Phe-Ile (VRFI), Tyr-Ile-Arg (YIR), Glu-Gln-Ile-Trp (EQIW), and His-Gly-Tyr-Lys (HGYK), exhibiting greater relative abundance in Glu-SFB than in SFB. At a dosage of 0.1 mg/mL, oligopeptide exhibits a greater capacity to diminish intracellular melanin levels and tyrosinase activity compared to 0.5 mg/mL kojic acid. Gly-SFB is prepared by replacing glucose with glycerol, the relative concentration of oligopeptides in Gly-SFB is positioned between that of SFB and Glu-SFB, while its whitening efficacy is similarly intermediate between SFB and Glu-SFB. Western blot research shown that all the S. epidermidis fermentation broths may suppress the expression of tyrosinase (TYR), tyrosinase-related protein-1 (TRP-1), tyrosinase-related protein-2 (TRP-2), and microphthalmia-associated transcription factor (MITF), which is the primary mechanism underlying the whitening impact of these broths.