Effects of ascorbic acid on α-l-arabinofuranosidase and α-l-arabinopyranosidase activities from Bifidobacterium longum RD47 and its application to whole cell bioconversion of ginsenoside

Bifidobacterium longum RD47 was cultured in 24 kinds of modified MRS broths containing various ingredients to select the most promising source that induces microbial enzymes. Among the various ingredients, ascorbic acid significantly enhanced α-l-arabinofuranosidase and α-l-arabinopyranosidase activities in Bifidobacterium longum RD47. Addition of 2 % ascorbic acid (w/v) to MRS showed the maximum enzyme activities. Both whole cell and disrupted cell homogenates showed efficient ρ-nitrophenyl-β-d-glucopyranoside and ρ-nitrophenyl-β-d-glucofuranoside hydrolysis activities. The initially enhanced α-l-arabinopyranosidase and α-l-arabinofuranosidase activities by ascorbic acid were maintained over the cell disruption process. The optimal pH of α-l-arabinofuranosidase and α-l-arabinopyranosidase was 5.0 and 7.0, respectively. Both enzymes showed the maximum activities at 40.0 °C. Under the controlled condition using Bifidobacterium longum RD47, ginsenoside Rb2, and Rc were converted to ginsenoside Rd.