Abstract: In this study, the fermentation supernatant, cells and disrupted cell supernatant of five strains of lactic acid bacteria (LAB) were screened for tyrosinase inhibitory activity and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity. The results showed that the tyrosinase inhibitory activity of the fermentation supernatant was much higher than that of the cells and the disrupted cell supernatant. The percentage inhibition of tyrosinase activity by the fermentation supernatant of strain MNJ-9 was 68.9% compared to only 50.9% with the cells and 34.8% with the disrupted cell supernatant. The fermentation supernatant of strain MNJ-9 scavenged 93.1% of DPPH radical. Meanwhile, MNJ-9 was identified by 16S rDNA gene sequencing. The major components of the fermentation supernatant of MNJ-9 were investigated using untargeted metabolomics based on liquid chromatography-mass spectrometry (LC-MS). The tyrosinase inhibitory activity and DPPH radical scavenging capacity of 10 of the major components were measured. The results showed that 5-aminovaleric acid had the highest tyrosinase inhibitory activity and DPPH radical scavenging capacity. The cytotoxicity of 5-aminovaleric acid on mouse melanoma cells (B16F10), and its impact on the melanin content and tyrosinase activity of B16F10 cells were determined to evaluate its whitening ability. The results showed that the cell survival rate was equal to or over 80% after culture for 72 h with 70 μg/mL of 5-aminovaleric acid, indicating no apparent cytotoxicity. At 5-aminovaleric acid concentrations of 10–70 μg/mL, the intracellular melanin content and tyrosinase activity were 85.4%–45.2% and 76.53%–40.5%, respectively. This indicates that 5-aminovaleric acid has some whitening ability.

Key words: Lactobacillus; tyrosinase inhibition; 1,1-diphenyl-2-picrylhydrazyl radical; fermentation supernatant; 5-aminopentanoic acid; B16F10 cells