Abstract:

In this work, Staphylococcus epidermidis （S. epidermidis） was used to prepare the fermentation broths with antioxidant activity. Through the optimization of the carbon source, three kinds of S. epidermidis fermentation broth were obtained and designated as SFB, Gly-SFB, and Glu-SFB, which were cultivated in beef protein medium and the beef protein medium supplemented with glycerol or glucose, respectively. The differences in antioxidant efficacy of SFB, Gly-SFB and Glu-SFB were investigated by evaluating intracellular ROS fluorescence intensity, SOD enzyme activity and MDA concentration. Gly-SFB and Glu-SFB exhibited a greater capacity to eliminate ROS as compared to that of SFB. The intracellular SOD enzyme activity increased as the concentrations of SFB and Gly-SFB increased. Nevertheless, the intracellular SOD enzyme activity was the highest after the treatment with Glu-SFB at the low concentrations. The intracellular MDA content reached a lower value after the treatment with Gly-SFB and Glu-SFB at lower concentrations, which was opposite to the case after the treatment with SFB. WB indicated that the S. epidermidis fermentation broth regulated the expression of relevant proteins in the Nrf2-Keap1 signaling pathway to exhibit the antioxidant effects. This indicates that the S. epidermidis fermentation broth promotes the expression of relevant proteins in the Nrf2-Keap1 signaling pathway, consequently, antioxidant benefits were exerted. The fermentation broth that were prepared by incorporating glycerol or glucose into the culture medium can augment their antioxidant activity.

Key words: S. epidermidis, fermentation broth, antioxidant, Western Blotting