Abstract

This paper describes the purification of a thermostable xylanase (Xyn) from a commercially available xylanase stock (Buzyme 2511 from Buckman Laboratories International, South Africa).The purified enzyme showed a Mr. of 66 kDa, and presented a dimeric form with two similar molecular weight chains of 33 kDa. The optimum pH and temperature were found to be 6.0 and 50°C, respectively. The enzyme was active over a broad pH (5 to 10) and temperature (50 to 90°C) range. The enzyme showed 90% residual activity at 70°C for more than 35 min. The substrate progress curve showed that the enzyme substrate reaction attains V_max within 30 min. The K_m value determined by Lineweaver-Burk Plot was 1 mg/ml by using birchwood xylan as a substrate. The inhibition of enzyme activity by chemical modifiers like o-phthaldehyde, trinitrobenzenesulphonic acid, diethyl pyrocarbonate and woodword’s reagent K  suggest the importance of Cys, His, Lys and Glu residues for the catalytic activity of the enzyme.

Key words: Xylanase, buzyme 2511, enzyme thermostability, steady state kinetics.