A typical endo-xylanase from Streptomyces rameus L2001 and its unique characteristics in xylooligosaccharide production

The activity of the extracellular xylanase produced by Streptomyces rameus L2001 against different xylans and xylooligosaccharides (XOS) was investigated. The main products of hydrolysis of birchwood xylan and oat-spelt xylan by the S. rameus L2001 xylanase were xylobiose (X2) and xylotriose (X3), suggesting that this is an endo-acting xylanase. This was confirmed by analysis of XOS degradation products. The enzyme hardly hydrolyzed X2 and X3, but hydrolyzed xylotetraose (X4) and xylopentaose (X5) producing mainly X2 and X3 through transglycosylation. Depending on the substrate, different quantities of reducing sugars were produced by the xylanase: 150 mg/g from corncob, 105 mg/g from bean culms, and 133 mg/g from bagasse. With the bagasse substrate, the xylanase yielded 2.36, 2.76, 2.03, and 2.17 mg/mL of X2, X3, X4, and X5, respectively. The structure of xylobiose and xylotriose from the hydrolysis of corncob xylan was identified by MS and NMR. The production of XOS from various agricultural wastes has potential industrial applications. This is the first report of XOS production by S. rameus L2001.