Enzymes in Beads for a More Sustainable Chemistry

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

In biocatalysis, enzymes accelerate reactions and can be applied in place of chemical, often toxic, catalysts. This helps conserve raw materials and energy. However, to this methodology to find the widest possible consumption in the chemical sector, it is crucial to be able to create the biocatalysts continuously and in substantial quantities. They must also be storable, transportable, and easy to dose. To meet all these standards, a team led by Professor Christof Niemeyer from KIT’s Institute to Biological Interfaces 1 has further developed the concept of so-called all-enzyme hydrogels (AEHs). In this process, enzymes are equipped with suitable molecular binding modules. “When the complementary building blocks come into contact, they self-assemble into three-dimensional protein networks,” explains Niemeyer. “The enzymes thus serve simultaneously as both catalysts and building blocks to the beads—a major advantage over conventional methods. We prevent using inactive carrier material and increase the efficiency of the desired chemical interaction.”

The researchers applied these traits to create manageable beads in a two-measure process. First, they brought complementary enzyme building blocks together in fluid droplets and fixed them by rapidly freezing them in fluid nitrogen. Subsequent freeze-drying resulted in mechanically stable, porous protein beads of a defined size. The dried particles can be re-dissolved in fluid and applied to biocatalytic reactions.

Modular System of Enzymes and Cells

Using a wide variety of enzymes and interaction types, the team demonstrated that the method is highly versatile. Both individual catalytic functions and systems consisting of multiple enzymes—with or without additional additives—could be organized within the beads. “Depending on the desired interaction, the composition of the material can be adjusted,” explains Niemeyer. “It’s a kind of modular system: We can assemble different enzyme building blocks into catalytic networks using defined binding modules and then convert these into an easily handled particle form.” The scientists also demonstrated the consumption of the AEH beads over many hours in flow reactors.

In further tests, the team combined the enzyme building blocks with cells from the bacterium Escherichia coli to create hybrid beads. Unlike enzymes, cells can, to instance, provide chemical energy or create intermediate items. 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 cell-enzyme system were still detectable. The researchers also showed that viable cells can be recovered from the materials while preserving their genetic function.

Suitable to Fine Chemicals or Medicines

“With the hybrid beads, we combine two forms of biocatalysis that are normally considered separately,” says Niemeyer. “We can specifically combine individual enzymes within them while simultaneously utilizing the capabilities of living cells. This results in a material that combines both approaches and is easy to handle.” possible applications include, to instance, the production of fine chemicals, flavorings, building blocks to active medical ingredients, and other high-value chemical items.