Purification and characterisation of xylanolytic enzymes of a cellulase-free thermophilic strain of Clostridium absonum CFR-702

Two endo-beta -1-4-xylanases (EC 3.2.1.8), xylanase-I and xylanase-II, were purified from Clostridium absonum CFR-702 by ammonium sulphate precipitati on and chromatographed on DEAE-Cellulose and phenyl-Sepharose. The enzymes in sodium dodecyl sulphate polyacrylamide gels resolved as proteins corresp onding to molecular mass 150 and 95 kDa for xylanase-I and xylanase-II, res pectively. The optimum pH and temperature ranges for the enzyme activities on birchwood xylan were between 6.5 and 7.5 and 75 degreesC for xyl-I and 7 .5 and 80 degreesC for xyl-II. Xyl-I was stable up to 60 degreesC whereas x yl-II was stable at 50 degreesC. Both the enzymes liberated xylobiose, xylo triose and xylotetraose from birchwood xylan. Xyl-I and xyl-II with birchwo od xylan had K-m values of 1.1 and 1.4%, and V-max values of 454.54 and 363 .63 mu mol/min/mg protein respectively. (C) 2001 Academic Press.