Heavily Engineered Enzyme Mixtures: A Novel Tool for Sustainable Plastic Recycling

| By Gizem Bulut

Scientific innovation meets molecular transformation: Enzyme engineering is the process of modifying enzymes, which are special proteins that can help chemical reactions happen faster and more efficiently. Scientists can modify these enzymes in order to make them better at doing their job, or even to give them new jobs that they couldn't do before! How does that work?

There are different ways that scientists can modify enzymes. One way is called directed evolution, which is a bit like selective breeding in animals. Scientists make small changes to the genes that code for the enzymes, and then test the new enzymes to see if they work better than the original ones. The best enzymes are kept, and then further modified in the same way. This process is repeated several times until the scientists have created an enzyme that works really well for its intended purpose.

Another way to modify enzymes is called rational design. This method uses computer simulations to predict how small changes to an enzyme's structure might affect its function. Scientists can then use this information to make specific changes to the enzyme's genes, and then test the new enzyme to see if it works better than the original one. Enzyme engineering is an important area of research because it can help scientists create new and better ways of doing things, such as breaking down environmental pollutants. By improving enzymes, scientists can make chemical reactions more efficient, more cost-effective, and better for the environment.

Plastic waste is a big problem for the environment because it doesn't break down easily (or at all). But some special enzymes, called plastic-degrading enzymes, can help break down the plastic into smaller pieces that are easier for other microorganisms to digest. However, these enzymes don't always work very well on their own, and they may not be able to break down all types of plastic. This is where enzyme engineering comes in. Scientists can modify the plastic-degrading enzymes to make them more effective at breaking down plastic waste. For example, scientists can modify the shape of the enzyme to better fit the shape of the plastic molecules, allowing the enzyme to break down the plastic more. They can also increase the amount of enzyme produced, or change the specific parts of the enzyme that interact with the plastic molecules to make them more effective. After enzyme engineering, the modified enzymes can then be used in a variety of ways to break down plastic waste. One way is to use them in bioreactors, which are large tanks that contain microorganisms that break down plastic waste. The modified enzymes can be added to the bioreactor to help break down the plastic more efficiently. Another way to use modified enzymes is to create new types of biodegradable plastics that break down more easily in the environment. They can be used in the production process to help break down the plastic into smaller, biodegradable pieces.

At present, there is a growing demand for sustainable solutions to manage plastic waste. One promising approach to address this challenge is the use of enzymes to break down plastics into their basic building blocks. This is called enzyme-based plastic recycling and it is what we do here with MIX-UP!

How MIX-UP works:

First, the unsorted plastic waste needs to be mechanically pre-treated. A further preliminary step before the actual upcycling is to produce enzymes in defined microbial mixed cultures and synthesized them in an optimized production reactor (enzyme production).

Next, the shredded waste is exposed to those engineered enzyme blends to hydrolyze the polymers into their smaller components (mono- and oligomers). For this first and essential step (plastic depolymerization), a mixture of different enzymes is required that can handle the different types of plastic present.

The released plastic mono- and oligomers from the various plastics types are transferred to a mixed culture bioreactor. Here, this mono- and oligomers can be used as plastic-derived feedstock and fed to dedicated microbial communities able to bioconvert these components into new components. Afterward, these new components provide the building blocks for the synthesis of novel biopolymers e.g. the bioplastics like polyhydroxyalkanoates / PHA.

These enzymes are designed to be more effective at breaking down plastics than natural enzymes. This means they can work faster and more efficiently, which is important for large-scale recycling operations. Another advantage is that they can be designed to be selective, which means they can target specific types of plastics, making the recycling process more efficient and reducing the amount of waste generated. Of course, the use of heavily engineered enzyme mixtures can result in important environmental benefits, as they can help reduce the amount of plastic waste that ends up in landfills or in the ocean!

But there are also some limitations to it: The development and production of heavily engineered enzyme mixtures can be expensive, which can make them less economically viable for some recycling operations, and also technically challenging. There may be limitations on the types of plastics they can break down effectively. It is also important to note that engineered enzyme mixtures are a relatively new technology, and there may be safety concerns associated with their use.

Enzymatic engineering has the potential to be an important tool in the fight against plastic waste, but its use must be carefully evaluated to ensure that they are economically feasible, safe, and effective.

The use of enzymes for plastic recycling is a relatively new field that is still in its early stages of development. Several research projects as well as start-up companies are working to develop and commercialize enzyme-based plastic recycling technologies, and many established players in the chemical industry are also exploring this field. The current state of the market for enzyme-based plastic recycling is one of rapid growth and innovation. The market for enzyme-based plastic recycling is expected to grow significantly in the coming years due to increasing public awareness of the environmental impact of plastic waste and a growing demand for sustainable solutions.