Research

Small spheres save enzymes for biocatalysis

Plasmas can supply the co-substrate for the biocatalysis of valuable substances, but pity the enzymes. If the latter are attached to small spheres, they work protected and up to 44 times longer.

Some enzymes, such as the one from fungi studied here, are able to produce valuable substances such as the fragrance (R)-1-phenylethanol. To do this, they convert a less expensive substrate using a cosubstrate. A research team from the Department of Biology at Ruhr-Universität Bochum came up with the idea of supplying them with this cosubstrate via a plasma - a crazy idea, as plasmas generally have a destructive effect on biomolecules. However, using several tricks, the researchers led by Prof. Dr. Julia Bandow and Dr. Tim Dirks succeeded. They have now refined one of these tricks and thus improved the process: they attach the enzymes to small balls to hold them to the bottom of the reactor and like this protect them from the harmful influence of the plasma. By choosing the most suitable type of ball, they were able to increase the stability of the enzyme 44-fold. They report in the Journal of the Royal Society Interface from October 25, 2023.

Model enzyme from an edible mushroom

"In plasma-driven biocatalysis, we want to operate enzymes that use hydrogen peroxide to convert a substrate into a more valuable product using technical plasmas," explains Julia Bandow, Head of the Chair of Applied Microbiology. The plasmas - energetically charged gases - produce hydrogen peroxide as well as a variety of reactive species.

The researchers use the non-specific peroxigenase (AaeUPO) from the edible fungus Agrocybe aegerita as a model enzyme. In initial studies, they were able to show that although plasma-driven biocatalysis works with it, there are also key limitations. "The decisive factor was that the enzymes react sensitively to the plasma treatment and are therefore inactivated within a short period of time," explains Tim Dirks, first author of the current study. "To prevent this, we use the method of enzyme immobilization, i.e. attaching the enzymes to so-called beads: small spheres with a porous surface."

Spheres keep the enzymes at the bottom

Due to gravity, these spheres lie on the bottom of the sample and provide a protective zone between the plasma phase at the top and the enzymes. The research team observed early on that the choice of different immobilization methods also led to different survival rates of enzymes. The aim of the current study was therefore to investigate the effect of different immobilization methods on the plasma stability of enzymes using a larger selection of enzymes.

Five different enzymes were selected, two of which also convert hydrogen peroxide and three of which do not require hydrogen peroxide for their activity. The researchers tested nine different types of beads, some of which had a resin surface and others a silica surface with or without a polymer coating. After immobilization, the enzymes were treated with plasma for up to five minutes. The researchers then compared their residual activity with untreated controls.

The path to new applications

The beads with resin surfaces showed the best results for all five enzymes. "The amino and epoxy-butyl beads performed best," like these," says Tim Dirks. In both cases, the enzymes form a strong, covalent bond with the carrier material, which cannot be dissolved. "This type of immobilization appears to limit the mobility of the enzymes, which makes them less susceptible to plasma-induced inactivation," concludes Tim Dirks. The team extended the plasma treatment times for the most promising candidates to up to one hour and, like this, was able to increase the stability of the enzymes under plasma treatment by up to a factor of 44 through immobilization. "The findings of this study thus pave the way for new applications that aim to combine enzymes with technical plasmas in the future," the researchers like this.

adapted from Maike Drießen, RUB

Awards

Prof. Dr. Beatriz Roldán Cuenya honored with Manchot Research Professorship

Prof. Beatriz Roldán Cuenya was awarded the Manchot Research Professorship, becoming the first woman to receive this prestigious honor. The award is presented annually by the Jürgen Manchot Foundation to outstanding scientists. In addition to recognizing her exceptional scientific contributions, the foundation provides the opportunity for the award winner to teach at the Chemistry Faculty of the Technical University of Munich.

Internationalization

Judith Golda Shines at AVS 69th International Symposium

Judith Golda, representing CRC 1316, captivated audiences at the AVS 69th International Symposium in Portland, Oregon, from November 5-10, 2023. Her invited talk, "Fundamentals of atmospheric pressure discharges for plasma catalytic applications," highlighted the critical role of atmospheric pressure discharges in plasma catalysis. Her presentation presented theory and application, emphasizing the transformative potential of understanding these discharges for catalytic processes in industries, environmental remediation, and energy production.

Project Area Meetings

CRC 1316 Project Area A (November 9) and Project Area B (November 10)

The CRC 1316 (Collaborative Research Center) brought together members from Project Area A on November 9 and Project Area B on November 10 for two consecutive days of intensive discussions, presentations, and collaborations. The primary objective of the meeting was to review recent project developments, share results, and facilitate further cooperation among team members.

The meeting commenced with a welcome address, setting the stage for a day of fruitful discussions. Each sub-project presented its recent findings, outlining progress, challenges faced, and proposed strategies for overcoming obstacles. The presentations sparked engaging discussions, providing valuable insights and suggestions from fellow researchers.