Driss Dorra, Haddar Anissa, Ghorbel Raoudha, Chaabouni Semia Ellouz
Unité Enzymes et Bioconversion, Ecole Nationale d'Ingénieurs de Sfax, Université de Sfax, route de Soukra, 3038, Sfax, Tunisia,
Appl Biochem Biotechnol. 2014 Jul;173(6):1405-18. doi: 10.1007/s12010-014-0932-0. Epub 2014 May 7.
Penicillium occitanis xylanase 2 expressed with a His-tag in Pichia pastoris, termed PoXyn2, was immobilized on nickel-chelate Eupergit C by covalent coupling reaction with a high immobilization yield up to 93.49 %. Characterization of the immobilized PoXyn2 was further evaluated. The optimum pH was not affected by immobilization, but the immobilized PoXyn2 exhibited more acidic and large optimum pH range (pH 2.0-4.0) than that of the free PoXyn2 (pH 3.0). The free PoXyn2 had an optimum temperature of 50 °C, whereas that of the immobilized enzyme was shifted to 65 °C. Immobilization increased both pH stability and thermostability when compared with the free enzyme. Time courses of the xylooligosaccharides (XOS) produced from corncob xylan indicated that the immobilized enzyme tends to use shorter xylan chains and to produce more xylobiose and xylotriose initially. At the end of 24-h reaction, XOS mixture contained a total of 21.3 and 34.2 % (w/w) of xylobiose and xylotriose with immobilized xylanase and free xylanase, respectively. The resulting XOS could be used as a special nutrient for lactic bacteria.
在毕赤酵母中表达的带有His标签的奥克西坦青霉木聚糖酶2（称为PoXyn2），通过共价偶联反应固定在镍螯合Eupergit C上，固定化产率高达93.49%。进一步评估了固定化PoXyn2的特性。固定化未影响最适pH，但固定化PoXyn2比游离PoXyn2表现出更偏酸性且更宽的最适pH范围（pH 2.0 - 4.0），游离PoXyn2的最适pH为3.0。游离PoXyn2的最适温度为50℃，而固定化酶的最适温度变为65℃。与游离酶相比，固定化提高了pH稳定性和热稳定性。由玉米芯木聚糖产生低聚木糖（XOS）的时间进程表明，固定化酶倾向于利用较短的木聚糖链，并且最初产生更多的木二糖和木三糖。在24小时反应结束时，固定化木聚糖酶和游离木聚糖酶作用下的XOS混合物中木二糖和木三糖的含量分别为21.3%和34.2%（w/w）。所得的XOS可用作乳酸菌的特殊营养物质。
