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Xylanases produced from a locally isolated strain of Thermomyces lanuginosus and its mutant derivative were purified to a yield of 39.1 and 42.83% with specific activities of 15,501 and 17,778 IU mg -1 protein, respectively. The purification consisted of two steps i.e., ammonium sulphate precipitation, and gel filtration chromatography. The mutant enzyme showed high affinity for substrate, with a K m of 0.098 mg ml -1 as compared to wild type enzyme showing K m of not less than 0.112 mg ml -1 . It was found that pH values of 8.1 and 7.3 were best for activity of the mutant and wild-type-derived enzymes, respectively. The values of pK a of the acidic limbs of both enzymes were the same (5.0 and 4.9, respectively) but the pK a value of the basic limb was slightly increased, indicating the participation of a carboxyl group present in a non-polar environment. Temperatures of 70 and 65°C were found optimal for mutant and wild-derived xylanase, respectively. Enzymes displayed a high thermostability showing a half life of 31.79 and 6.0 min (5.3-fold improvement), enthalpy of denaturation (DH*) of 146.06 and 166.95 kJ mol -1 , entropy of denaturation (DS*) of 101.44 and 174.67, and free energy of denaturation (DG*) of 110.25 and 105.29 kJ mol -1 for mutant-and wildorganism derived enzyme, respectively at 80°C. Studies on the folding and stability of cellulase-less xylanases are important, since their biotechnological employments require them to function under extreme conditions of pH and temperature. The kinetic and thermodynamic properties suggested that the xylanase from the mutant organism is better as compared to xylanase produced from the wild type and previously reported strains of same species, and may have a potential usage in various industrial fields.

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The effect of carbon source and its concentration, inoculum size, yeast extract concentration, nitrogen source, pH of the fermentation medium, and fermentation temperature on beta-glucosidase production by Kluyveromyces marxianus in shake-flask culture was investigated. These were the independent variables that directly regulated the specific growth and beta-glucosidase production rate. The highest product yield, specific product yield, and productivity of beta-glucosidase occurred in the medium (pH 5.5) inoculated with 10% (v/v) inoculum of the culture. Cellobiose (20 g/L) significantly improved beta-glucosidase production measured as product yield (YP/S) and volumetric productivity (QP) followed by sucrose, lactose, and xylose. The highest levels of productivity (144 IU/[L.h]) of beta-glucosidase occurred on cellobiose in the presence of CSL at 35 degrees C and are significantly higher than the values reported by other researchers on almost all other organisms. The thermodynamics and kinetics of beta-glucosidase production and its deactivation are also reported. The enzyme was substantially stable at 60 degrees C and may find application in some industrial processes.