Study On The Properties Of Xylanase From Yeast

Xylanase can hydrolyze xylan in wheat-based diet to reduce the viscosity in the digestive tract, destroy the cell wall and release the nutrients from the cell, and so increase the utilization of the feed. The expression system of Pichia pastor is is one of the standard tools to express the recombinant protein in the molecule biology field. In order to make clear of the properties of xylanase expressed in Pichia pastoris, experiments in vivo and in vitro were conducted to study the characterizations of the xylanase.First, basic properties (including the optimal pH and pH stability, optimal temperature and themal stability, parameters of the reaction kinetics, the substrate specificity and effect of proteases on the xylanase activity) of xylanase were studied by the method of reductive sugar (3,5-Dinitrosalicylic acid,DNS). The result showed that the optimal pH of the xylanase was 6. 1 when reacted in different pH buffer. It had a good stability between pH5 and 10 when incubated at 37, 40, 50℃ for 30min and 60min, and no effect of treated time on xylanase activity was obtained. The optimal temperature of the enzyme was 51℃. When kept in the water with the temperature of 50, 60, 70, 80, 90, 100℃ for 30min, the enzyme activity was reduced as the rise of the temperature and had a good stability when the temperature was below 60℃. The Km value and Vmax of xylanase for oat spelts xylan under 51℃, pH6.1 were 6.49mg·mL^-1 and 21. 05μg·mL^-1·min^-1, respectively. The enzyme activity was only 74. 21% when birchwood xylan was used as substrate compared with oat spelts xylan as substrate. Treated by pepsin for 30, 60, 120min under 37℃, xylanase activity was only 1.08% left at 60min, but the activity was little affected by trypsin treatment with 80.95% remaining at 120min.To study the enzyme stability in'digestive tract of growing pigs, 10 pigs were randomLy divided into 2 treatments to feed a diet with 0.1% or 1.0% xylanase. Pigs were fed 4 days before the formal trial. On the fifth day, pigs were fed each 15min and killed 2 hours after feeding and the chyme was collected...