壳聚糖固定D-阿洛酮糖3-差向异构酶转化D-阿洛酮糖

Immobilization of D-psicose 3-epimerase on chitosan for D-psicose conversion

D-阿洛酮糖3-差向异构酶是一种能催化D-果糖转化为D-阿洛酮糖的异构酶。本实验采用壳聚糖作为载体制备固定化D-阿洛酮糖3-差向异构酶,考察了固定化酶的制备条件和酶学性质,并研究在填充床中利用固定化D-阿洛酮糖3-差向异构酶持续转化D-果糖。实验结果表明:固定时间为3h,酶∶载体=15∶1(U/g),其酶活回收率达到45%。相比游离酶,固定化酶具有更高的温度稳定性以及在较宽的pH范围内保持较高酶活,其最适温度和pH分别为60℃与8.5。固定化酶在填充床中反应的最高转化率为24%,在最佳流速2.5mL/min下其转化率为19%,相关产率为6.7g/L·h,经过168h的反应,其转化率仍然保持在13%以上。

D-Psicose 3-epimerase （DPE）was an enzyme that catalyzed the reversible isomerization between D-fructose and D-psicose. In this study, the chitosan was used as carrier to immobilize the D-psicose 3-epimerase. The preparation conditions and enzymatic properties of the immobilized enzyme were studied and the packed-bed was then employed for continuous conversion from D-fructose to D-psicose by immobilized DPE.The activity recovery was 45% after 3h immobilization where the ratio of enzyme to carrier was 15：1 U/g.As compared with free enzyme, the immobilized DPE showed much higher tolerance for pH and heat.The optimal temperature and pH of the immobilized enzyme increased to 60℃ and 8.5, repectively.ln the packed-bed reactor,the highest reaction yield of 24% was obtained with immobilized enzyme. Furthermore, the productivity of 6.7g/L. h was achieved with the yield of 19% at the optimal flow rate of 2.5mL/min.After 168h reaction,the reaction yield was still maintained at 13%.