Production of eriodictyol and dihydrotricetin from naringenin by recombinant tyrosinase of Bacillus megaterium DY804 strain

Tyrosinase hydroxylates monophenols to ortho-diphenols through monophenolase activity and oxidizes the ortho-diphenols to ortho-quinones through diphenolase activity. Here, the biotransformation of naringenin, a flavonoid having various biological activities, was attempted using a recombinant tyrosinase of Bacillus megaterium DY804 strain (DY804) as a biocatalyst. DY804 sequentially produced two hydroxylated products, eriodictyol (a catechol) and dihydrotricetin (a gallol), from naringenin (a phenol) in the presence of L-ascorbic acid. The kcat and Km values of DY804 toward naringenin were 161 min−1 and 1060 μM, respectively, to produce eriodictyol. When eriodictyol was the substrate, the kcat and Km of DY804 were 25.7 min−1 and 130 μM, respectively. The maximum concentrations of eriodictyol and dihydrotricetin produced by DY804 were 1074 μM (54% yield) and 315 μM (16% yield), respectively. The maximum productivities were 1038 μM/h (299 mg/L/h) of eriodictyol and 241 μM/h (73 mg/L/h) of dihydrotricetin. The activity of 3-hydroxy-3-methyl-glutaryl-coenzyme A (HMG-CoA) reductase was reduced by naringenin, eriodictyol, and dihydrotricetin, their half maximal inhibitory concentration (IC50) values were 1192, 2401, and 751 µM, respectively. Therefore, three tested flavonoid compounds can be used as antihyperlipidemic agents. It is suggested that DY804 can be applied in the pharmaceutical industry as a biocatalyst to produce high-value-added flavonoids.