Purification and Characterisation of Xylanolytic Enzymes of a Cellulase-free Thermophilic strain of Clostridium absonum CFR-702

Two endo-β-1-4-xylanases (EC 3.2.1.8), xylanase-I and xylanase-II, were purified fromClostridium absonum CFR-702 by ammonium sulphate precipitation and chromatographed on DEAE-Cellulose and phenyl-Sepharose. The enzymes in sodium dodecyl sulphate polyacrylamide gels resolved as proteins corresponding to molecular mass 150 and 95 kDa for xylanase-I and xylanase-II, respectively. The optimum pH and temperature ranges for the enzyme activities on birchwood xylan were between 6.5 and 7.5 and 75°C for xyl-I and 7.5 and 80°C for xyl-II. Xyl-I was stable up to 60°C whereas xyl-II was stable at 50°C. Both the enzymes liberated xylobiose, xylotriose and xylotetraose from birchwood xylan. Xyl-I and xyl-II with birchwood xylan had K_mvalues of 1.1 and 1.4%, and V_maxvalues of 454.54 and 363.63 μmol/min/mg protein respectively.