Enzymes in globules for more sustainable chemistry

Thanks to biocatalysis with enzymes, an enormous range of active medical ingredients and other complex molecules can be synthesized in an environmentally friendly manner. Researchers at the Karlsruhe Institute of methodology (KIT) have now developed a methodology that can be applied to assemble enzymes into millimeter-sized, storable globules. The enzymes are not only catalysts, however also form the material of the beads. In another variant, the enzyme networks can be combined with living cells. The process has been filed to a patent. Results in cutting-edge Materials.

In biocatalysis, enzymes accelerate reactions and can be applied instead of chemical, often toxic catalysts. This helps save raw materials and energy. In order to this methodology to be applied as broadly as possible in the chemical sector, however, it is crucial to provide the biocatalysts continuously and in substantial quantities. In addition, they must be storable, transportable and easy to dose. In order to meet all these standards, a team led by Professor Christof Niemeyer from the Institute to Biological Interfaces 1 of KIT has further developed the concept of the so-called all-enzymes hydrogel (AEHs). In this process, enzymes are equipped with suitable molecular binding modules. “If the complementary building blocks meet, they organize themselves into three-dimensional protein networks,” explains Niemeyer. “The enzymes are thus at the same time the catalyst and the building material of the beads-a great advantage over conventional processes. We prevent inactive carrier material and increase the efficiency of the desired chemical interaction.”

The researchers leveraged these traits to create manageable beads in two steps. First, they brought together complementary enzyme building blocks in fluid droplets and fixed them in fluid nitrogen through rapid freezing. The subsequent freeze-drying produced mechanically stable, porous protein beads with a defined size. The dried particles can be put back into fluid and applied to biocatalytic reactions.

Modular system of enzymes and cells

Using very different enzymes and interaction types, the team showed that the process can be applied in many ways. Both individual catalytic functions and systems made up of several enzymes-with or without additional auxiliary substances-could be organized in the beads. “The composition of the material can be adjusted depending on the desired interaction,” says Niemeyer. “This is a kind of modular system: we can assemble different enzyme building blocks to form catalytic networks using defined binding modules and then convert them into a well-handled particle shape.” The scientists also demonstrated the consumption of AEH beads in flow reactors to many hours.

In further tests, the team combined the enzyme building blocks with cells from the bacterium Escherichia coli and applied them to create hybrid beads. In contrast to enzymes, cells can, to instance, provide chemical energy or generate intermediates. The hybrid beads remained catalytically active even after greater than four weeks of dry storage at room temperature. Even after five months of storage, the functions of the cellular enzyme system could still be detected. The researchers also showed that viable cells can be reclaimed from the materials, whereby the genetic function is preserved.

Suitable to fine chemicals or pharmaceuticals

“With the hybrid beads, we combine two forms of biocatalysis that are normally considered separately,” says Niemeyer. “We can specifically combine individual enzymes with one another and at the same time consumption the capabilities of living cells. This creates a material that combines both approaches and is easy to handle. ”Possible areas of consumption are, to instance, the production of fine chemicals, flavorings, medical active ingredient components and other high-condition chemical items.