Utility of Thermostable Xylanases of Mycothermus thermophilus in Generating Prebiotic Xylooligosaccharides.

Xylooligosaccharides as emerging prebiotics are able to promote the growth of probiotic bacteria. In the present study, four neutral, thermostable xylanases (MtXyn11A, MtXyn11At, MtXyn11B, and MtXyn11C) from compost fungus Mycothermus thermophilus CGMCC3.18119 were overexpressed in Pichia pastoris GS115 and used to produce xylooligosaccharides from beechwood xylan. The enzymes showed similar enzymatic properties (maximal activities at pH 6.0-6.5 and 65 °C) but varied in catalytic efficiency and cleaving actions. MtXyn11A, MtXyn11At, and MtXyn11C mainly produced xylobiose (59-62%), xylose (16-20%), and xylotriose (16-19%), while MtXyn11B released xylobiose (51%), xylotriose (32%), and xylose (12%) as the main products. When using the xylan hydrolysates of different xylanases as the carbon source, four probiotic Lactobacillus strains Lactobacillus brevis 1.2028, Lactobacillus rhamnosus GG, Lactobacillus casei BL23, and Lactobacillus plantarum WCSF1 were confirmed to use the xylooligosaccharides efficiently (83.8-98.2%), with L. brevis 1.2028 as the greatest.