Improved Expression and Characterization of a Multidomain Xylanase from Thermoanaerobacterium aotearoense SCUT27 in Bacillus subtilis

A xylanase gene was cloned and characterized from Thermoanerobacterium aotearoense SCUT27, which was attested to consist of a signal peptide, one glycoside hydrolase family 10 domain, four carbohydrate binding modules, and three surface layer homology domains. The change of expression host from Escherichia coli to Bacillus subtilis resulted in a 4.1-fold increase of specific activity for the truncated XynAΔSLH. Five different versions of secretion signals in B. subtilis indicated that it was preferably routed via a Sec-dependent pathway. Purified XynAΔSLH showed a high activity of 379.8 U/mg on beechwood xylan. XynAΔSLH was optimally active at 80 °C, pH 6.5. Thin layer chromatography results showed that xylobiose and the presumed methylglucuronoxylotriose (MeGlcAXyl₃) were the main products liberated from beechwood xylan catalyzed by the recombinant xylanase. All of the results suggest that XynAΔSLH is a suitable candidate for generating xylooligosaccharides from cellulosic materials for industrial uses.