Bioactive water powders for catalysis in biphasic systems

生物催化剂在化学合成中的应用具有巨大的潜力，因为它们可以提高合成的经济效率和环境友好性。然而，一个主要的缺点是它们需要水性环境才能活化。因此，几乎不涉及在水中具有低溶解度或稳定性的化合物，这些化合物是合成中的大部分有机化合物。该项目旨在通过引入生物活性水粉末作为新颖、廉价和易于操作的工具来拓宽生物催化合成的范围，以使酶在有机反应介质中的应用成为可能。酶被“封装”在其水相中的小颗粒中。这是通过疏水性二氧化硅颗粒在酶溶液周围形成稳定的壳来实现的。已经证明，这样的颗粒在有机溶剂中形成稳定的乳液（皮克林乳液），并且允许生物催化剂的活性的相当大的改进，特别是对于敏感酶。然而，由于仍然需要有机相来获得乳液，因此不能避免在生产过程中对酶稳定性的负面影响和导致的催化剂失活。此外，在有机-水环境中的乳液的形成不能标准化。为了解决这些问题，在这个项目中，建议使用干水粉末（DWPs），即在空气中产生的颗粒稳定的水相，用于酶包封，然后将其置于有机溶剂中。以前从未描述过DWP的这种使用。因此，将对所需的材料特性以及该方法对酶及其催化效率的影响进行彻底的基础研究。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，该系统将在迭代过程中朝着综合适用性发展，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酶，并评估合成性能。其中，这将包括最近描述的（假）麻黄碱脱氢酶催化各种对映体纯的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.