Efficient production of icariin and baohuoside I from Epimedium Folium flavonoids by fungal α- l -rhamnosidase hydrolysing regioselectively the terminal rhamnose of epimedin C

Abstract

Abstract Industrial application of icariin and baohuoside I has been hindered by the short supply to a great extent. In this work, a novel GH78 α- l-rhamnosidase AmRha catalyzed the bioconversion of low-value epimedin C in crude Epimedium Folium flavonoids (EFs) to icariin and baohuoside I was developed. Firstly, the high-level expression of AmRha in Komagataella phaffii GS115 attained an enzyme activity of 571.04 U/mL. The purified recombinant AmRha could hydrolyze α-1,2-rhamnoside bond between two rhamnoses (α-Rha(2 → 1)α-Rha) in epimedin C to produce icariin with a molar conversion rate of 92.3%, in vitro. Furtherly, the biotransformation of epimedin C to icariin by the recombinant Komagataella phaffii GS115 cells was also investigated, which elevated the EFs concentration by fivefold. In addition, biotransformation of epimedins A-C and icariin in the raw EFs to baohuoside I was fulfilled by a collaboration of AmRha and β-glucosidase/β-xylosidase Dth3. The results obtained here provide a new insight into the preparation of high-value products icariin and baohuoside I from cheap raw EFs.

Keywords

• α- l-Rhamnosidase
• Icariin
• Baohuoside I
• Epimedium Folium flavonoids
• Biotransformation