The recovery and bioproperties of a xylanolytic multi-enzyme complex from Tepidimicrobium xylanilyticum BT14

Abstract

To retain its biological activity and conformation as well as to preserve the multiple protein components, a xylanolytic multi-enzyme complex (XMEC) was isolated from a growth culture of Tepidimicrobium xylanilyticum BT14 to homogeneity by a mild isolation method using ultrafiltration, polysaccharide binding affinity, and gel filtration chromatographic techniques. The isolated XMEC was active at neutral and alkaline pH, showing 100% of the maximal xylanase activity at pH 6.5 and more than 50% at pH 9.0. It exhibited a temperature optimum at 60°C (pH 6.5) and maintained its full activity at 60°C for 180min; its half-life at 70°C was up to 90min. The XMEC was highly resistant to various metal ions, including Ca2+, Mn2+, K+, Ni2+, Zn2+, Mg2+ and Fe2+, but not to Cu2+ and Hg2+. It hydrolysed xylans including birchwood xylan, oat spelt xylan, and highly substituted rye arabinoxylan to principally yield xylobiose and xylotriose. The presence of sugars including xylose, glucose and cellobiose, as well as the presence of ethanol stimulated the xylanase activity. These results indicate that the XMEC has potential in such xylan-related bioconversion industries as bioethanol production.