Characterization of a novel GH10 thermostable, halophilic xylanase from the marine bacterium Thermoanaerobacterium saccharolyticum NTOU1

The thermophilic bacterium Thermoanaerobacterium saccharolyticum NTOU1 was isolated from a hydrothermal vent near Taiwan. A complete gene, xynFCB, encoding 413 amino acids and belonging to the glycosyl hydrolyase family 10 (GH10) of xylanases was identified from the genome sequence of strain NTOU1. This gene was cloned and expressed in Escherichia coli BL21(DE3)pLys. The enzyme was purified by Nickel affinity chromatography and had a molecular mass of 50 kDa. XynFCB hydrolyzed xylan with optimal activity at 63°C and pH 6.4, and preferentially hydrolyzed oat spelt xylan. The enzyme retained more 70% of its activity between the pH values of 5.5-8.0, and its half-life was 55 min at 65°C. XynFCB displayed enhanced activity in a dose-dependent manner in 0-12.5% (w/v) NaCl. Optimal activity was observed in 12.5% (w/v) NaCl, while 67% of its activity was retained in 15% (w/v) NaCl after a 48-h incubation. This is the first report describing the cloning, expression and characterization of a thermostable, halophilic xylanase from T. saccharolyticum.