PURIFICATION AND PROPERTIES OF AN ENDOXYLANASE FROM A CORN STALK ROT STRAIN OF ERWINIA-CHRYSANTHEMI

An extracellular xylanase (EC 3.2.1.8) was purified approximately 20-fold from liquid cultures of Erwinia chrysanthemi strain SR120A grown with glycerol as a carbon source. Ammonium sulphate fractionation, cation-exchange chromatography (CM-Sephadex), chromatofocusing, and gel filtration (Sephadex G-75) isolated the enzyme from culture filtrates. The xylanase had a molecular mass of approximately 42 kDa and had a pI of 8.8. The pH optimum was 5.5, and the temperature optimum in a 10-min assay was 55 C. About 40% of the enzyme activity was lost after incubating for 1 h at 40 C. The enzyme was shown to be an endoxylanase, cleaving xylan polymers internally. The xylanase and an endopectate lyase (EC 4.2.2.2) isolated from E. chrysanthemi were tested, both alone and together, for cell-killing and tissue-macerating ability on oat, corn, and selected dicotyledonous plants. The xylanase demonstrated both a cell-killing and a tissue-macerating capability on grasses.