Immobilization And Application Of The Hyperthermophilic Xylanase B From Thermotoga Maritima

The hyperthermophilic xylanase B (XynB) from Thermotoga maritima expressed in E. coli has expert alkaline-tolerant and thermostability, even under the conditions of 100℃ and pH 6.5~8.5. Hence, hyperthermophilic xylanase B is a promising xylanase applied in pre-bleaching and oligo-xylo-saccharides production. In order to increase the production efficiency of the xylanase and decrease the cost of production xylanase, this research studied the immobilization of xylanase B. The main research content includes the following: Optimising the culture conditions of the recombinant xyalanse B expressed in E. coli; Selecting the suitable carriers for xylanase B and optimising the conditions of immobilization; Properties of the immobilized xylanase B on Eudragit S-100 and the application in pulp bleaching; Immobilization of xylanase B using novel chelate-epoxy supports and production of oligo-xylo-saccharides in packed bed. The results showed that:(1) Both the culture density and activity of xylanase induced by lactose were higher than those induced by IPTQ actually, the activity of xylanase induced by lactose was 2591 U/100mL which was 973 U/100mL higher than that induced by IPTG The results confirmed that lactose could be used as an inducer in the fermentation process.(2) The activity yield of XynB on Eupergit S-100 is up to 90% and, while the chelate-epoxy supports shows over 65% of the activity yield.(3) The XynB can be purified by the Eudragit S-100 while immobilization. The immobilized XynB on Eudragit S-100 exhibited the same optimum pH (6.2), 5℃ higher optimum temperature and higher thermostability than the free XynB. Thus, the reversibely soluble-insoluble immobilized XynB should be significant for treatment of paper pulp bleaching in paper industry.(4) Compared to the free XynB, the immobilized XynB on Ni-E also exhibited the same optimum pH (6.2), wider pH stability, 5℃ higher optimum temperature and higher thermostability. The hydrolysis rate of the substance is upto 60% in packed bed, which is 16% higher than the hydrolysis rate when using free XynB. In interval hydrolysis (45 min each time at 90 ℃), the half life of the immobilized XynB on Ni-E is 62 times. During consecutive hydrolysis in packed bed (90℃), the half life of the immobilized XynB on Ni-E is 445 h.