Bioactive water powders for catalysis in biphasic systems

生物催化剂在化学合成中的应用具有广泛的工业潜力，因为它们可以提高合成的经济效率和环境友好性。然而，它们的一个主要缺点是要求水环境是活跃的。因此，在水中溶解度或稳定性较低的化合物（这些化合物是合成中的大多数有机化合物）几乎不能参与。该项目旨在扩大生物催化合成的范围，通过引入生物活性水粉末作为一种新颖、廉价和易于操作的工具，使酶在有机反应介质中的应用成为可能。酶将被“封装”在水相中的小颗粒中。这是通过疏水二氧化硅颗粒在酶溶液周围形成稳定的外壳来实现的。已经证明，这种颗粒在有机溶剂中形成稳定的乳剂（皮克林乳剂），并允许生物催化剂活性的显著提高，特别是对敏感酶。然而，由于仍然需要有机相来获得乳液，因此在生产过程中对酶的稳定性产生负面影响以及导致催化剂失活是不可避免的。此外，乳剂在有机-水环境中的形成也不能标准化。为了解决这些问题，本项目建议使用干燥水粉（DWPs），即在空气中产生的颗粒稳定水相，在将其置于有机溶剂之前对酶进行包封。dwp的这种使用以前从未被描述过。因此，将对所需的材料性质以及该方法对酶及其催化效率的影响进行深入的基础研究。在吉林大学（中国）和德累斯顿工业大学（德国）的材料科学家和酶技术专家的密切合作下，该系统将在一个迭代过程中朝着合成适用性的方向发展，并以现有的替代方法为基准。最好的变体将装载不同的、工业相关的酶，并评估其合成性能。其中，这将包括最近描述的（伪）麻黄碱脱氢酶催化各种对映体纯α -羟基酮的不对称合成。

The use of biocatalysts in chemical synthesis holds enormous potential for a wide range of industries as they can increase the economic efficiency as well as the environmental friendliness of syntheses. However, a major drawback is their requirement of aqueous environment to be active. Thus, compounds with low solubility or stability in water, which are the majority of organic compounds in synthesis, can be hardly involved. This project aims to widen the scope of biocatalyzed syntheses by introducing bioactive water powders as novel, cheap and easy-to-handle tools to enable enzyme application in organic reaction media. The enzymes are to be "encapsulated" in small particles within their aqueous phase. This is achieved by hydrophobic silica particles that form a stable shell around the enzyme solution. It has already been demonstrated that such particles form stable emulsions (Pickering emulsions) in organic solvents and allow a considerable improvement of the activity of the biocatalysts, especially for sensitive enzymes. However, since an organic phase is still required to obtain the emulsion, negative effects on enzyme stability during the production process and resulting inactivation of the catalysts could not be avoided. In addition, the formation of the emulsions in the organic-aqueous environment cannot be standardized. To solve these problems, employment of dry water powders (DWPs), i.e. particle-stabilized water phases produced in air, for enzyme encapsulation prior to their subjection to organic solvents is suggested in this project. Such a use of DWPs has never been described before. Thus, a thorough fundamental study on the required material properties and the effects of the approach on enzymes and their catalytic efficiency will be performed. In close collaboration of material scientists and enzyme technologists at Jilin University (China) and TU Dresden (Germany), respectively, the system will be developed towards synthetic applicability in an iterative process and benchmarked against existing alternative approaches. The best variants will be loaded with different, industrially relevant enzymes and evaluated for synthetic performance. Among others, this will include recently described (pseudo)ephedrine dehydrogenases catalysing the asymmetric synthesis of various enantiomerically pure alpha-hydroxyketones.