Efficient production of isoquercitin, icariin and icariside II by a novel thermostable α-l-rhamnosidase PodoRha from Paenibacillus odorifer with high α-1, 6-/α-1, 2- glycoside specificity.

Minor flavonoids, such as isoquercitin, icariin and icariside II, have desired bioactivity and bioavailability. To enhance the production efficiency on converting rutin and epimedin C into minor flavonoids, a novel GH family 78 α-l-rhamnosidase PodoRha from the Paenibacillus odorifer was cloned and heterologous over-expressed in E. coli BL21 (DE3). PodoRha exhibited a high catalytic ability in cleaving outer α-1, 2-rhamnopyranosyl moieties of epimedin C and α-1, 6-rhamnopyranosyl of rutin. It displayed the highest activity at 45°C and pH 6.5, and has great thermostability at 40°C. Under the optimal transformation condition (40°C, pH 6.5, 1 h incubation), 10g/L of Rutin was 99.86% transformed into 6.95g/L of isoquercitin by PodoRha with a crude productivity of 6.95g. L^-1. H^-1; 1.964g/L icariin was detected after the epimedin C of the total Epimedium flavonoids (10g/L) were 99.98% converted by PodoRha. Moreover, by using a two-stage conversion system with a crude icariside...