Screening and identification of microbial strains that secrete an extracellular C-7 xylosidase of taxanes

World Journal of Microbiology and Biotechnology (Impact Factor: 1.35). 01/2011; 27(3):627-635. DOI: 10.1007/s11274-010-0499-z

ABSTRACT This paper reported a novel strain screen strategy for the production of C-7 xylosidase of taxane for the biotransformation
of 7-xylosyl-10-deacetylpaclitaxel (7-XAP) to 10-deacetylpaclitaxel (10-DAP) using xylan as the sole carbon and energy source.
The C-7 xylosidase produced by the four strains obtained was an extracellular inducible enzyme enabling the biotransformation
to be carried out directly in microbial suspension cultures. The four strains were identified as Streptomyces matensi, Arthrobacter nicotianae, Achromobacter piechaudii, and Pseudomonas
plecoglossicida by morphological, physiological, and genetical characteristics. Several chemicals were confirmed as activating the enzyme
activity, in which magnesium acetate improved the maximal substrate concentration from 0.1 to 0.5gl−1 at complete transformation in S. matensi suspension cultures. The non-mucous, extracellular activity and high substrate concentration characters of S. matensi facilitate both the upstream production of the enzyme, and downstream extraction and purification of the enzyme and the product.

KeywordsC-7 xylosidase of taxane–7-xylosyl-10-deacetylpaclitaxel–10-deacetylpaclitaxel–
Streptomyces matensi
Achromobacter piechaudii

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    ABSTRACT: 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 β-xylosidase activity of 9.6 U l(-1) was achieved. The β-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 β-xylosidases capable of removing the C-7 xylosyl group from 7-xylosyltaxanes.
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