Karlsruhe Institute Of Technology Develops Biocatalytic Foams With Tremendous Durability And Activity
Industrial biocatalysis with enzymes is considered a “game changer” in the development of a sustainable chemical industry. With the help of enzymes, an impressive range of complex molecules such as active pharmaceutical ingredients can be synthesized under environmentally friendly conditions. Researchers at the Karlsruhe Institute of Technology (KIT) have now developed a new class of materials by producing enzymes as foams that have enormous durability and activity. The researchers report on their results in the journal Advanced Materials . The innovative manufacturing process for the enzyme foams has already been patented. ( DOI: 10.1002/adma.202303952 )
In order to further develop the field of industrial biocatalysis, which is mainly used in the production of pharmaceuticals and specialty chemicals, researchers are working intensively on new process technologies. In biocatalysis, enzymes accelerate the reactions instead of chemical catalysts, which saves raw materials and energy. The aim now is to provide enzyme biocatalysts continuously and in large quantities under the most gentle conditions possible. The enzymes are immobilized in microstructured flow reactors so that efficient material conversions can be realized. They are spatially fixed and bound to an inert material and are therefore restricted in their mobility, which leads to a higher concentration of the enzymes and thus to higher productivity.
Foamed micro-droplets of self-assembling enzymes
Normally, enzymes change their structure during foaming and thus lose their biocatalytic activity. However, the new protein foams have enormous durability and activity. The activity is a measure of the effectiveness of the enzyme, which ensures that the starting materials react with each other as quickly as possible. To produce the protein foams, two dehydrogenase enzymes are mixed that have matching linkage sites so that they can spontaneously form a stable protein network. “This mixture is then mixed with a gas stream in a microfluidic chip so that microscopic bubbles of a uniform size form in a controlled manner,” explains Professor Christof Niemeyer from the Institute for Biological Interfaces-1.
“These are monodisperse “full enzyme foams”, i.e. three-dimensional, porous networks that consist exclusively of biocatalytically active proteins,” says Niemeyer, characterizing the composition of the new materials. The stable hexagonal honeycomb structure of the foams has an average pore diameter of 160 µm and a lamella thickness of 8 µm and is formed after a few minutes from the freshly produced spherical bubbles of approximately the same size.
Use active and stable full enzyme foams efficiently
In order to be able to use enzymes efficiently for material conversions, they have to be immobilized in large quantities under the mildest possible conditions in order to maintain their activity. To date, enzymes have been immobilized on polymers or carrier particles, but this requires valuable reactor space and activity can be compromised. “Compared to the “full enzyme hydrogels” we have already developed, the new foam-based materials have a significantly larger surface area on which the desired reaction can take place,” says Niemeyer, describing the major improvement. In contrast to theoretically expected results, the new foams surprisingly show a remarkably high durability, mechanical resistance and catalytic activity of the enzymes,
The researchers suspect that the stability is due to the matching linkage sites with which the enzymes are equipped. This allows them to self-assemble and form a highly cross-linked lattice during drying, which gives the new material unique stability. “Amazingly, after drying for four weeks, the newly developed enzyme foams are significantly more stable than the same enzymes without foams,” explains Niemeyer, “this is of great interest for marketing, as it simplifies stock production and shipping considerably.”
The new biomaterials open up diverse avenues for innovations in industrial biotechnology, materials science and food technology. For example, the protein foams could be used in biotechnological processes to produce valuable compounds more efficiently and sustainably. The research team was able to show that the foams can be used to produce the industrially valuable sugar tagatose, which represents a promising alternative to refined sugar as a sweetener.