CHARACTERIZATION AND ANALYSES OF STABILITY OF BACTERIAL XYLANASE

Abstract

Xylanases, including endo-B-D-1,4-xylanase (EC 3.2.1.8) and B-D-xylosidase (EC 3.2.1.37), are complex enzyme that hydrolyze xylan to xylo-oligosacharide and xylose. The xylan degrading enzyme can be produced by aerobic or anaerobic mesophilic or thermophilic microbe. The objectives of this study were to characterize and analyze the stability of gcylanase obtained from xylanolytic bacterial isolate. Xylanolytic isolates were isolated from Crabs by using Hungate method and screened for the highest enzymatic activity. The xylanolytic bacterial isolate were then cultivated for xylanase production. To produce xylanases, the isolate was grown in a medium using oat spelt xylan as substrate under anaerobic condition at 35°C and pH 1 1 for 7 days. The culture supernatant was separated by centrifuging and used as the source of xylanase. The supernatant obtained was concentrated by the addition with ammonium sulphate at levels of saturation of 70%. Concentrated supernatant was then dialyzed against 10 mM acetate buffer. Then the enzyme obtained was purified using ion-exchange (DEAE-cellulose) chromatography. Purified enzyme was characterized its optimum activity under different pH buffer condition (4 - 8), temperature (30 - 60°C) and substrate concentration (xylan). The results showed that the purified enzyme had the highest activity at pH 4.5 (0.962 U/mg) and temperature 50°C (0.846 U/mg). The value of K”, and I/,,,a, were 83.33 mg ml" and 69.93 U mg" respectively. It was also found that xylanase isolated from xylanolytic bacteria having stability at pH 4-7.