Molecular cloning of a xylanase gene from Streptomyces sp. No. 36a and its expression in streptomycetes.

The gene for an extracellular xylanase from Streptomyces sp. No. 36a was cloned into Streptomyces lividans TK21 using pIJ702 as a vector plasmid. The smallest DNA fragment encoding the xylanase gene and its possible promotor was determined to be a 1.04 kb Sph I-Sac I fragment by sub-cloning studies. This xylanase gene fragment was transferred into the pSK2 series of plasmids and introduced into Streptomyces kasugaensis G3 protoplasts. The cloned xylanase gene was expressed in both S. lividans TK21 and S. kasugaensis G3, and these clones produced and secreted high yields of xylanase into the culture medium. The xylanase production was not detected when a foreign DNA fragment was inserted into the Bcl I site locating in the xylanase gene fragment.