초록
<P><B>Abstract</B></P> <P>A thermostable β-xylosidase gene <I>Tpexyl3</I> from <I>Thermotoga petrophila</I> DSM 13,995 was cloned and overexpressed by <I>Escherichia coli</I>. Recombinant Tpexyl3 was purified, and its molecular weight was approximately 86.7 kDa. Its optimal activity was exhibited at pH 6.0 and 90 °C. It had broad specificity to xylopyranosyl, arabinopyranosyl, arabinofuranosyl and glucopyranosyl moieties. The β-xylosidase activity of the recombinant Tpexyl3 was 6.81 U/mL in the LB medium and 151.4 U/mL in a 7.5 L bio-reactor. It was applied to transform ginsenoside extract into the pharmacologically active minor ginsenoside 20(S)-Rg3, which was combined with thermostable β-glucosidase Tpebgl3. After transforming under optimal condition, the 20 g/L of ginsenoside extract was transformed into 6.28 g/L of Rg3 within 90 min, with a corresponding molar conversion of 95.0% and Rg3 productivity of 1793.49 mg/L/h, respectively. This study is the highest report of a GH3 family glycosidase with arabinopyranosidase activity and also the first report on the high substrate concentration bioconversion of ginsenoside extract to ginsenoside 20(S)-Rg3 by using two thermostable glycosidases.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A thermostable glycosidase was cloned and characterized from <I>T. petrophila</I> DSM 13995. </LI> <LI> The enzyme is a multi-functional hydrolase with high specificity to arabinofuranosyl. </LI> <LI> The enzyme provided the basis for efficient bioconversion of ginsenoside extract. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>