Purification and Binding Properties of a Low Molecular Weight Xylan-Binding Endoxylanase (29 kDa) from Bacillus circulans B-6

Abstract

Bacillus circulans B-6 produced extracellular xylanolytic and cellulolytic enzymes when grownin a medium containing xylan as a carbon source. Purification of xylan-binding xylanase wasperformed from the culture medium by specific adsorption and desorption on insoluble xylan. Themolecular mass of purified xylanase was estimated to be 29 kDa, which showed only xylanaseactivity. The enzyme was stable at pH 6.0 to 7.0 and temperature up to 40 ํC. The pH andtemperature optima were 7.0 and 60 ํC, respectively. The purified enzyme hydrolyzed xylan to aseries of short-chain xylooligosaccharides as the product, indicating that the enzyme was anendoxylanase. The xylan-binding endoxylanase could effectively hydrolyze low substituted insolublexylan of birch wood more than larch wood and oat spelt xylans. The purified enzyme bound toinsoluble xylan and avicel but the binding was affected by pH, sugars and metal ions.

Keywords : Adsorption and Desorption on Insoluble Xylan / Bacillus circulans B-6 / Purificationof Xylanase / Xylan-binding Endoxylanase