Production and Purification of a Novel Xanthan Lyase from a Xanthan-DegradingMicrobacteriumsp. Strain XT11

A xanthan lyase was produced and purified from the culture supernatant of an excellent xanthan-modifying strain Microbacterium sp. XT11. Xanthan lyase was induced by xanthan but was inhibited by its structural monomer glucose. Its production by strain XT11 is much higher than that by all other reported strains. The purified xanthan lyase has a molecular mass of 110 kDa and a specific activity of 28.2 U/mg that was much higher than that of both Paenibacillus and Bacillus lyases. It was specific on the pyruvated mannosyl residue in the intact xanthan molecule, but about 50% lyase activity remained when xanthan was partially depyruvated. Xanthan lyase was optimally active at pH 6.0–6.5 and 40°C and alkali-tolerant at a high pH value of 11.0. The metal ions including K + , Ca 2+ , Na + , Mg 2+ , Mn 2+ , and Li + strongly stimulated xanthan lyase activity but ions Zn 2+ and Cu 2+ were its inhibitor. Xanthan lyase should be a novel enzyme different from the other xanthan lyases ever reported.