Reprogramming wood-degrading mushroom enzymes for the biorecycling of plastic
INRAE - National Research Institute for Agriculture, Food and Environment
Plastic pollution is ubiquitous in the environment and managing plastic waste is a global problem. In addition to developing more reasonable production methods and ways to use plastic, one solution to the problem is to develop biorecycling technology. The very nature of plastic, made with highly resistant polymers in order to not break down, makes this a huge scientific challenge. Yet, plastic shares analogous properties with other – natural – recalcitrant polymers, like wood cellulose, which can be broken down by filamentous fungi. The fungi achieve this by secreting an arsenal of enzymes. They notably secrete very special enzymes known as “lytic polysaccharide monooxygenases”, or LPMOs, capable of breaking down the surface of cellulose to then weaken it and make complete degradation easier. These properties make the LPMOs perfect candidates for engineering to create new functions like breaking down plastics.
Chimera enzymes that recognise plastics
LPMO enzymes are usually composed of two modules: a binding module that enables it to recognise and bind to a specific polymer – cellulose, in a natural setting – and a catalytic module that breaks down the cellulose surface. Scientists focused on replacing the binding module with other modules, using industrially scaled protein engineering processes to make the enzymes capable of binding to different plastics. They created chimera LPMOs that can recognise and bind to different types of plastics. Some were also able to make holes in the surface of polyhydroxyalkanoate, a biosourced plastic known as PHA.
The researchers will now evaluate how well these chimera enzymes break down different types of plastics in order to select the most effective ones, to further engineer them and combine them into enzyme ‘cocktails’ with the objective of creating an enzymatic tool kit for the biorecycling of plastics.
Journal
Chem & Bio Engineering
Article Title
Design of PlasDesign of Plastic Binding Lytic Polysaccharide Monooxygenases via Modular Engineering
Do fungi recognize shapes?
image:
Fungal mycelial networks connecting wood blocks arranged in circle (left) and cross (right) shapes.
view moreCredit: ©Yu Fukasawa et al.
Can organisms without a brain still show signs of intelligence? Researchers at Tohoku University and Nagaoka College had this question in mind when conducting a study to measure the decision-making processes in fungi. While it may sound like science fiction, this level of basal cognition is possible even in fungi.
"You'd be surprised at just how much fungi are capable of," remarks Yu Fukasawa of Tohoku University, "They have memories, they learn, and they can make decisions. Quite frankly, the differences in how they solve problems compared to humans is mind-blowing."
Fungi grow by releasing spores, which can germinate and form long, spidery threads underground (a mycelium). We typically only see the tiny mushrooms on the surface without realizing that there's a vast network of interconnected mycelium beneath our feet. It is through this network that information can be shared, somewhat like neural connections in the brain.
The present study examined how a wood-decaying mycelial network responded to two different situations: wood blocks placed in a circle versus cross arrangement. For example, if the fungi didn't display decision-making skills, they would simply spread out from a central point without consideration for the position of the blocks. Remarkably, this is not what the researchers witnessed.
For the cross arrangement, the degree of connection was greater in the outermost four blocks. It was hypothesized that this was because the outermost blocks can serve as "outposts" for the mycelial network to embark in foraging expeditions, therefore more dense connections were required. In the circle arrangement, the degree of connection was the same at any given block. However, the dead centre of the circle remained clear. It was proposed that the mycelial network did not see a benefit in overextending itself in an already well-populated area.
These findings suggest that the mycelial network was able to communicate information about its surroundings throughout the entire network, and change its direction of growth accordingly based on the shape.
Our comprehension of the mysterious world of fungi is limited, especially when compared to our knowledge of plants and animals. This research will help us better understand how biotic ecosystems function and how different types of cognition evolved in organisms.
These results were published in Fungal Ecology on September 12, 2024.
Journal
Fungal Ecology
Article Title
Spatial resource arrangement influences both network structures and activity of fungal mycelia: A form of pattern recognition?
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