Enzymatic hydrolysis of 7-xylosyltaxanes by an extracellular xylosidase from Cellulosimicrobium cellulans

To find extracellular biocatalysts that can specifically and efficiently remove the C-7 xylosyl group from 7-xylosyltaxanes. A Cellulosimicrobium cellulans strain F16 that can remove the C-7 xylosyl group from 7-xylosyltaxanes was isolated from the root soil of an old Taxus yunnanensis tree. Using corn cob as sole carbon source, the maximum 7-xylosyl-10-deacetylpaclitaxel beta-xylosidase activity of 9.6 U l(-1) was achieved. The beta-xylosidase could be trapped by a ceramic tubular membrane (pore size 50 nm), and exhibited an apparent molecular weight much greater than 500 kDa. Under optimized conditions, 3.75 l cell-free culture medium transformed 2 grams 7-xylosyltaxane mixtures to their corresponding aglycones within 3 h, with a conversion > 98 %. This is the first report that C. cellulans can produce extracellular beta-xylosidases capable of removing the C-7 xylosyl group from 7-xylosyltaxanes.