Purification Of Xylanase Using Affinity Filtration

Xylan, the major component of hemicullulose, is the second abundant renewable energy source in the earth. It serves as the main carbon source for various kinds of microorganisms which could secret a series of xylanolytic enzymes. These xylanolytic enzymes act synergetically to hydrolyze the xylan to xylooligosaccharide and xylose. Xylanolytic enzymes have potential applications in a wide range of industrial fields, such as bioconversion, food, animal feed, pulp and paper,energy sources, et al.In this paper, the adsorption and desorption of xylanase were investigated. Effects of guanidine hydrochloride, different concentrations of buffer and different temperatures on the adsorption characters of sorbents were investigated. The influences of pH, ion strenth on the affinity adsorption of xylanase was also discussed. As could be seen from the experimental results that asorption equilibriums were rapidly established in about three hours. The adsorption equilibria of xylanase on xylan was in good accordance with the Langmuir isotherm model.Adsorption was prompted by the decrease of salt concentration , the affinity interaction between xylanase and xylan decreases with the increase in pH of buffer. The influence of salt concentration on xylanase adsorption could be well explained by the affinity adsorption theory. Electrostatic interaction may influence the adsorption of xylanase to xylan. The xylanase was desorbed from the xylanase-xylan complex by changing pH and ionic strength.Affinity filtration has received significant attention in recent decades because it can provide reliable and efficient method for the purification of biomolecules, by integrating membrane technology and affinity chromatography. Affinity filtration can meet the demands in the applications as wastewater treatment, purification of proteins, removal of endotoxin, blood purification. In this paper, the xylanase was purified by the affinity interaction. The xylanase-xylan complex was separated from unwanted molecules by microfiltration using nylon membrane and the complex was retained. The xylanase was eluted by changing pH and ionic strength. Microfiltration was carried out then to isolate xylanase as microfiltrate. xylan was recovered as retentate. It was found that purification by affinity microfiltration gives xylanase with high yields. The technique is challenging because of simpleness , inexpensiveness , and less time-consuming. It's easier to be scaled up than convention methods, too.Basic enzymatic characteristic of obtained xylanase were studied, which relative molecular weight was 26.9kDa,29.5kDa. The optimal pH of two xylanase was at pH 5.5, pH 4.5. The optimal temperature was 55℃, 45℃,while in the temperature upon 80℃,they lost their activity quickly.