ACHEMA Pulse 2021

••• 18••• Branchennews Biofunctionalized materials Enzymes successfully embedded in plastics I n general, plastics are processed at way over a hundred degrees Celsius. Enzymes, by contrast, can- not usually withstand these high temperatures. Researchers at the Fraunhofer Institute for Applied Polymer Research IAP have man- aged to reconcile these contra- dictions: They are able to embed enzymes in plastics without the enzymes losing their activity in the process. The potentials this creates are enormous. Materials that clean themselves, have anti-mold surfaces or are even self-degrading are just a few examples of what will be possi- ble if we manage to embed active enzymes into plastics. But for the enzyme-specific properties to be transferred to the materials, the enzymes must not suffer damage as they are embedded in the plastic. Scientists at Fraunhofer IAP have developed a solution to the prob- lem as part of the “Biofunction- alization/Biologization of Polymer Materials BioPol” project. Since summer 2018, the project has been running in cooperation with BTU Cottbus-Senftenberg. The Ministry of Science, Research and Culture of the State of Brandenburg is funding the project. “It was clear from the outset that we were not looking to produce biofunctionalized plastics on a lab- oratory scale. We wanted to take a giant step to show that techni- cal production is possible,” says Dr. Ruben R. Rosencrantz, Head of the “Biofunctionalized Materials and (Glyco)Biotechnology” depart- ment at Fraunhofer IAP, summariz- ing the ambitious project goals. At around the midpoint in the project, major breakthroughs are already emerging: Enzymes have been suc- cessfully embedded, both in terms of the enzymes themselves and the processing technique. Inorganicprotective carriers forhigher tem- peraturestability Seeking a way to stabilize the en- zymes, the researchers use inor- ganic carriers. These carriers act as a kind of protection for the en- zyme. As Rosencrantz explains: “We use inorganic particles, for example, which are highly porous. The enzymes bind to these carri- ers by embedding in the pores. Al- though this restricts the enzymes’ mobility, they remain active and are able towithstandmuch higher tem- peratures.” Rosencrantz does stress, however, that there is no generally applica- ble stabilization process: “No two enzymes are alike. The carrier and the technology most suitable for the embedding process remain en- zyme-specific.” Stabilizedenzymes: notonlyat theplastic surface, but inside too The researchers deliberately sought a way of applying the stabilized en- zymes not only to the surface of the plastic, but of embedding them into the plastics directly. “Although far more difficult, this technique also prevents signs of wear on the material surface affecting the func- tionality of the plastics,” explains Thomas Büsse who heads the insti- tute’s processing pilot plant for bi- opolymers in Schwarzheide. In order to achieve an optimumma- terial result in the downstreampro- cess, the stabilized enzymes have to be distributed as quickly as pos- sible in the hot plasticmelt towhich they are added, without becoming exposed to excess force or elevated temperatures. A balancing act that tipped in Büsse’s favor: “We have developed a process that is suitable for both bioplastics and for the con- ventional petroleum-based plastics such as polyethylene. Our investi- gations also show that once em- bedded in the plastic, stabilized en- zymes are able to withstand higher thermal loads than before. This makes the use of enzymes and all process steps considerably easier.” Self-cleaningplastics are just thebeginning Until now, the researchers at Fraunhofer IAP have evaluated mainly proteases as their choice of enzyme. Proteases are able to break up other proteins. This lends the plastic functionalized by these proteases a self-clean- ing effect. Pipes, for example, would not close up or clog as readily. But other enzymes are being systematically tested as well. The cooperation partners at BTU Cottbus-Senftenberg are focusing more closely at enzymes for degrading plastics and toxic substances, for exam- ple. The first functionalized plastic granulates, films and injection molding bodies have already been produced. The researchers have estab- lished that the enzymes embed- ded in these products remain ac- tive. The next step now is to test and further optimize the pro- cess for everyday use in various applications. Rosencrantz and Büsse are optimistic – and have also submitted a patent applica- tion for their research. Production of a biofunctionalized film in the processing pilot plant. Foto: Fraunhofer IAP Determination of the enzymatic activity of a biofunc-tionalized plastic. Foto: Fraunhofer IAP