PURIFICATION AND PROPERTIES OF A XANTHAN DEPOLYMERASE FROM A HEAT-STABLE SALT-TOLERANT BACTERIAL CONSORTIUM

A bacterial consortium (NRRL B-14401) resulting from soil enrichment growth on xanthan gum produces enzymes that can degrade xanthan gum in salt-containing solutions at temperatures up to 65-degrees-C. One component that cleaves the backbone linkages of both xanthan gum and carboxymethyl cellulose is called xanthan depolymerase. Two such depolymerase activities were isolated by high performance anion exchange chromatography, and their molecular weights determined by size exclusion chromatography to be 170 000 and 100 000 Da. The 170-kDa protein was purified and its properties studied. Sodium chloride and potassium chloride enhanced the hydrolysis of carboxymethyl cellulose, but decreased the rate of degradation of xanthan gum. The purified enzyme, which was optimally active at pH 6, was less stable to extremes of temperature than crude mixtures of cell-free culture broth; stabilized by its substrate it was active for more than 6 h at 50-degrees-C.