School of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189, China.
ACS Appl Mater Interfaces. 2011 Sep;3(9):3300-7. doi: 10.1021/am200792a. Epub 2011 Aug 15.
Microfloccules of TiO(2) nanoparticles, on which glycerol-dehydrogenase (GDH), 1,3-propanediol-oxidoreductase (PDOR), and glycerol-dehydratase (GDHt) were coimmobilized, were prepared by adsorption-flocculation with polyacrylamide (PAM). The catalytic activity of immobilized enzyme in the glycerol redox reaction system, the enzyme leakage, stabilities of pH and temperature, as well as catalytic kinetics of immobilized enzymes relative to the free enzymes were evaluated. Enzyme loading on the microfloccules as much as 104.1 mg/g TiO(2) (>90% loading efficiency) was obtained under the optimal conditions. PAM played a key role for the formation of microfloccules with relatively homogeneous distribution of size and reducing the enzyme leakage from the microfloccules during the catalysis reaction. The stabilities of GDH against pH and temperature was significantly higher than that those of free GDH. Kinetic study demonstrated that simultaneous NAD(H) regeneration was feasible in glycerol redox system catalysted by these multienzyme microfloccules and the yield of 1, 3-popanediol (1, 3-PD) was up to 11.62 g/L. These results indicated that the porous and easy-separation microfloccules of TiO(2) nanoparticles with immobilized multienzymes were efficient in term of catalytic activity as much as the free enzymes. Moreover, compared with free enzyme, the immobilized multienzymes system exhibited the broader pH, higher temperature stability.
TiO(2)纳米粒子微絮凝体通过聚丙烯酰胺（PAM）的吸附絮凝作用制备，其中甘油脱氢酶（GDH）、1,3-丙二醇氧化还原酶（PDOR）和甘油脱水酶（GDHt）被共固定化。评价了甘油氧化还原反应体系中固定化酶的催化活性、酶泄漏、pH 和温度稳定性以及固定化酶相对于游离酶的催化动力学。在最佳条件下，TiO(2)上的酶负载量高达 104.1 mg/g（>90%的负载效率）。PAM 在形成具有相对均匀尺寸分布的微絮凝体方面起着关键作用，并减少了在催化反应过程中酶从微絮凝体中的泄漏。GDH 对 pH 和温度的稳定性明显高于游离 GDH。动力学研究表明，在这些多酶微絮凝体催化的甘油氧化还原体系中可以同时进行 NAD（H）再生，1,3-丙二醇（1,3-PD）的产量可达 11.62 g/L。这些结果表明，具有固定化多酶的多孔且易于分离的 TiO(2)纳米粒子微絮凝体在催化活性方面与游离酶一样高效。此外，与游离酶相比，固定化多酶体系表现出更宽的 pH 值和更高的温度稳定性。
