d-Psicose (d-ribo-2-hexulose or d-allulose) is the Carbon-3 epimer of d-fructose sugar and considered as an unnatural (rare) sugar found in low amount in nature. It has about 70% of the relative sweetness but 0.3% of the energy of sucrose, which is suggested as the most suitable sucrose substitute for food additives. Enzymatic biosynthesis using ketose 3-epimerases is a necessary procedure for the production of d-Psicose from d-fructose. However, significant drawbacks in the application of ketose 3-epimerases at industrial scale observe lower thermal stability as well as bioconversion efficiency, reusability and recovery of the enzyme. We have attempted immobilization of ketose 3-epimerases from Agrobacterium tumefaciens (agtu) d-psicose 3-epimerase (DPEase) on titanium dioxide. Further, Scanning electron microscopy (SEM), inverted microscopy, Fourier transform infrared spectroscopy (FTIR) and UV-vis spectroscopy showed that the enzyme was successfully immobilized on the titanium dioxide (TiO2) surface. Titanium dioxide immobilized agtu-DPEase (TiO2-agtu-DPEase) shows pH optima at 6.0 and 60 °C as a higher working temperature. TiO2-agtu-DPEase showed a half-life of 180 min at 60 °C, which is higher as compared to Agrobacterium tumefaciens (agtu) DPEase (3.99 min at 50 °C). At equilibrium, 36:64 (D-psicose: d-fructose), the bioconversion efficiency was accounted for titanium dioxide immobilized DPEase, which is higher than the agtu-DPEase. Titanium dioxide immobilized DPEase showed bioconversion efficiency up to 9 cycles of reusability.

中文翻译：

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将根癌农杆菌 D-阿洛酮糖 3-差向异构酶固定在二氧化钛上用于稀有糖的生物转化

d-Psicose（d-ribo-2-hexulose 或 d-allulose）是 d-果糖的碳 3 差向异构体，被认为是一种在自然界中发现的非天然（稀有）糖。它具有蔗糖的70%左右的相对甜度和0.3%的能量，被认为是最适合食品添加剂的蔗糖替代品。使用酮糖 3-差向异构酶进行酶促生物合成是从 d-果糖生产 d-Psicose 的必要程序。然而，在工业规模应用酮糖 3-差向异构酶的显着缺点观察到较低的热稳定性以及生物转化效率、酶的可重复使用性和回收率。我们已尝试将来自根癌农杆菌 (agtu) d-阿洛酮糖 3-差向异构酶 (DPEase) 的酮糖 3-差向异构酶固定在二氧化钛上。此外，扫描电子显微镜 (SEM)、倒置显微镜、傅里叶变换红外光谱 (FTIR) 和紫外-可见光谱表明该酶成功地固定在二氧化钛 (TiO2) 表面。二氧化钛固定的 agtu-DPEase (TiO2-agtu-DPEase) 在 6.0 和 60 °C 下显示出最佳 pH 值，因为工作温度较高。TiO2-agtu-DPEase 在 60 °C 下的半衰期为 180 分钟，与根癌农杆菌 (agtu) DPEase（50 °C 下为 3.99 分钟）相比更高。在平衡时，36:64（D-阿洛酮糖：d-果糖），生物转化效率由二氧化钛固定的 DPEase 决定，它高于 agtu-DPEase。二氧化钛固定的 DPEase 显示出高达 9 次可重复使用周期的生物转化效率。