Abstract:[Background] Tyrosinase is the key enzyme of melanin biosynthesis, which easily causes the pigment disorders and enzymatic browning of fruits and vegetables. At present, the development on tyrosinase inhibitor has obtained more and more attention. However some tyrosinase inhibitors have certain potential safety hazards, such as arbutin and kojic acid. Microorgansims are rich in resources and have many advantages. It has become a spot to search for tyrosinase inhibitors with strong specificity and high efficiency from microorganisms. [Objective] We investigated the effects of metabolite extracts of Salinicoccus ventosaetal strains B2-3-5 and B6-1-4 isolated from dabancheng Salt Lake of Urumqi in Xinjiang on tyrosinase activity. And also compared metabolic differences between the two strains during the fermentation. The aim of this study was to understand the inhibitory mechanism of tyrosinase activity of the strain B2-3-5. [Methods] Taken kojic acid as positive control, we determined the inhibitory effects of metabolite extracts produced by the two strains B2-3-5 and B6-1-4 on mushroom tyrosinase, respectively. We detected all the metabolites of the two strains under the same fermentation conditions by liquid chromatograph-mass spectrometer. We identified metabolic differences with univariate and multivariate analysis, Orthogonal Partial Least Squares-Discrimination Analysis (OPLS-DA) method. We carried out cluster analysis on the identified differential metabolites by Hierarchial Cluster Analysis (HCA) method and searched the differential metabolic pathways through the databases kyoto encyclopedia of genes and genomes (KEGG). [Results] These findings indicated that the inhibitory effects of metabolite extracts of the strain B2-3-5 on the diphenolase activity of mushroom tyrosinase was 67% and its IC50 was estimated as 0.277 mg/mL, while the metabolite extracts of the strain B6-1-4 among the same genus had no inhibitory activity. We obtained 63 differential metabolites from the two strains by metabolomics methods. The types and relative contents of amino acids, vitamins and carboxylic acids were significantly higher in B2-3-5 than those in B6-1-4. The results of metabolic pathway analysis showed that these differential metabolites were mainly participated in 15 metabolic pathways, among which vitamin B6 biosynthesis pathway had the highest correlation with differential metabolites and fermentation process. [Conclusion] We speculated that the strain B2-3-5 might increase the contents of some small molecular compounds such as amino acids, vitamins and carboxylic acids, etc. to inhibit the tyrosinase activity. The upregulation of vitamin B6 biosynthesis pathway also suggested that the strain had the inhibitory activity of tyrosinase through producing vitamin B6 to interact with the essential amino group in tyrosinase or scavenging the reactive oxygen species (ROS) during the enzymatic catalytic process.
