A thermophilic Anoxybacillus sp. strain JT-12, isolated from soil, produced acidic xylotriose, 4-O-methyl-alpha-d-glucuronosyl-xylotriose (MeGlcAX(3)), as a main product from birchwood xylan and accumulated them in the culture under optimum conditions at pH 7.0 and 55 A degrees C using 0.75% (w/v) birchwood xylan as a carbon source for 42-72 h. The acidic xylotriose was purified by ethanol precipitation and high-performance liquid chromatography using NH2 LichosherA (R) 100 column. The results of electrospray ionization mass spectrometry, mass to charge ratio (m/z) 603.23, confirmed that the purified sample was acidic xylotriose that had benefits and applications in many fields.