Step by step to the end product through enzyme catalysis

The production of the sugar trehalose, which is used as a functional food and additive in pharmaceutical products or in cosmetics, is teamwork for enzymes: One takes care of the construction of an energy-rich intermediate product (UDP-glucose), from which the second then produces trehalose. Flow catalysis makes the cooperation possible, although enzyme number one works at room temperature, while number two prefers temperatures above 50 degrees Celsius. This was demonstrated by the team led by Professor Dirk Tischler, head of the Microbial Biotechnology working group at the Ruhr University Bochum (RUB).

Sequential reactors

Enzymes, for example from bacteria, can convert a wide variety of starting materials into an abundance of target products. So-called white biotechnology should make use of this ability to produce chemicals in an environmentally friendly manner. Since it sometimes takes several catalysts and steps to manufacture the desired product, Dirk Tischler’s team, in collaboration with groups from the TU Delft, the TU Bergakademie Freiberg and the Silesian Technical University, designed a cascade for flow catalysis. The starting materials glucose and glucose-1-phosphate (activated form) as well as UTP (uridine triphosphate, a biochemical energy carrier) were converted into trehalose in two steps using immobilized enzymes. The first enzyme has the task of activating the glucose molecules, the second links them together. “Since one enzyme requires different working conditions than the other, we immobilized it in two successive reactors,” explains Dirk Tischler. For example, the researchers can set the temperature or the residence time of the substrates in the reactor independently of one another. “It would also be conceivable not only to link sugar with one another in this way, but also, for example, to breed drugs on sugar, such as antibiotics,” he says, looking to the future.

Printing on reusable substrates

In a follow-up project that he sponsored together with Hirsch Engineering Solutions and that is funded by the Federal Ministry for Economic Affairs and Energy, he is now concentrating on optimizing the cascade. The first aim is to improve the substrate materials for the enzymes. “The silicate substrates used up to now are not tolerated equally well by all enzymes,” says Tischler. In addition, they are often not reusable. Plastics, including those from biological sources, may be more suitable and can be shaped using 3D printing. “They have already proven their biocompatibility in various medical applications,” emphasizes the scientist.

On the other hand, the project partners want to make the enzyme cascade more cost-effective by adding a kinase that converts the separated UDP into UTP at the end of the reaction with the help of polyphosphate. This allows the cascade to be restarted. “Up to now we always had to add new UTPs to start the cascade, which is quite expensive,” explains Dirk Tischler. “If we could recycle it using polyphosphate, the costs would be significantly reduced.”

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