Potential of Candida utilis to ferment Ecklonia cava by-product for enhanced anti-methicillin-resistant Staphylococcus aureus (MRSA) activity

In order to utilize the by-product of Ecklonia cava (the remaining biomass of E. cava), microbial fermentation which may result in the production of bioactive compounds using the by-product was applied in this study. The fermentation broth of E. cava by-product fermented with Candida utilis showed enhanced antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) and food-borne pathogenic bacteria compared to that of control. To perform a more detailed investigation on the antibacterial activity, the broth was extracted with methanol and further fractionated with organic solvents. After 1 day of fermentation, the ethyl acetate (EtOAc) fraction exhibited the highest anti-MRSA activity with minimum inhibitory concentration ranging from 64 to 256 μg mL−1, suggesting that the fermentation of E. cava by-product with C. utilis could enhance antibacterial activity against MRSA. In addition, high-performance liquid chromatography analysis revealed that dieckol, eckol, eckstolonol, and triphlorethol-A contents in the EtOAc-soluble extract increased significantly. The anti-MRSA activity of E. cava by-product most probably originated from phlorotannins, and the fermentation of C. utilis may have stimulated the breakdown of phlorotannins or have increased the efficiency in extracting phlorotannins.