The identification, purification, and characterization of STXF10 expressed in Streptomyces thermonitrificans NTU-88

Multiple xylanolytic enzymes of Streptomyces thermonitrificans NTU-88 were induced by oat-spelt xylan and separated by two-dimensional polyacrylamide and zymogram gels. Nineteen clear spots differed in pI and molecular weight values were found on the zymogram, and only spot one was seen on the corresponding silver-stained gel. These results revealed that multiple xylanases were secreted when S. thermonitrificans NTU-88 was induced and the spot (STXF10), identified as being a glycosyl hydrolase family 10 xylanase, was the predominant one among xylanases. STXF10 showed a tolerance for high temperatures and broad pH ranges and high affinity and hydrolysis efficiency for xylans. Furthermore, it also featured the minor ability to degrade different lignocellulosic substrates. Although S. thermonitrificans NTU-88 possesses multiple xylanases, our results suggest that the major form of xylanase might be selectively and specifically induced depending on the type of substrate to which the microorganism is exposed.