Researchers at Washington State University (WSU) and the Northwest Pacific National Laboratory (PNNL) of the Department of Energy have devised an artificial enzyme that digests lignin, which has stubbornly resisted previous attempts to convert it. the in an economically useful source of energy. An open access document on his work is published in Communications of nature.
Lignin is found in all vascular plants, where it forms cell walls and provides stiffness to plants. Lignin allows trees to be maintained, gives firmness to vegetables, and accounts for about 20-35% of the weight of wood. Because lignin turns yellow when exposed to air, the wood products industry removes it as part of the fine paper manufacturing process. Once removed, lignin often burns inefficiently to produce fuel and electricity. Chemists have tried and failed for over a century to make valuable products from lignin.
Our bio-imitating enzyme was promising in the degradation of real lignin, which is considered a breakthrough. We believe that there is an opportunity to develop a new class of catalysts and to really address the limitations of biological and chemical catalysts.
—Xiao Zhang, co-author and associate professor at WSU
Zhang also has a joint appointment with the PNNL.
This is the first mimetic enzyme in nature that we know can efficiently digest lignin to produce compounds that can be used as biofuels and for chemical production.
—Chun-Long Chen, co-author and PNNL researcher
Chen is also an associate professor of chemical and chemical engineering at the University of Washington.
In nature, fungi and bacteria are able to break down lignin with their enzymes, which is how a trunk covered with mushrooms in the forest breaks down. Enzymes offer a much more environmentally benign process than chemical degradation, which requires a lot of heat and consumes more energy than it produces. However, natural enzymes degrade over time, making them difficult to use in an industrial process. They are also expensive.
It is very difficult to produce these enzymes from microorganisms in a significant amount for practical use. Then, once isolated, they are very fragile and unstable. But these enzymes offer a great opportunity to inspire models that copy their basic design.
“Xiao Zhang.”
In the current study, researchers replaced the peptides surrounding the active site of natural enzymes with protein-like molecules called peptoids. These peptoids then self-assembled into nanoscale crystalline tubes and sheets.
… We have developed a class of self-assembled peptoid / hemin (Pep / hemin) nanomaterials with adjustable active sites and microenvironments that mimic peroxidases for lignin depolymerization, taking advantage of the high tuning of peptoids (or poly-substituted glycines) and the uniqueness of its self-assembled crystalline nanomaterials in the alignment of active sites. Compared to peptides, peptoids can be easily synthesized to achieve a greater diversity of side chains while having much higher chemical and thermal stabilities. Our recent work has shown that the tuning of amphiphilic peptoids can lead to the formation of hierarchically structured crystalline nanomaterials, including membrane mimetic 2D nanosheets and nanotubes.
These peptoid-based nanomaterials are highly stable under various pH conditions and at high temperatures. The new functionalities and applications of peptoid nanomaterials can be easily realized by adjusting the chemistry of the side chain and incorporating and aligning different functional groups. Due to their high tuning and stability, peptoid nanomaterials are promising for creating optimal active sites and microenvironments. All of these unique properties suggest that crystalline nanomaterials based on peptoids offer great opportunities to develop peroxidase mimetics.
“Jian.” et al.
Peptoids were first developed in the 1990s to mimic the function of proteins. They have several unique features, including high stability, that allow scientists to address deficiencies in natural enzymes. In this case, they offer a high density of active sites, which is impossible to obtain with a natural enzyme.
We can accurately organize these active sites and adjust their local environments for catalytic activity, and we have a much higher density of active sites, rather than an active site.
“Chun-Long Chen.”
As expected, these artificial enzymes are also much more stable and robust than natural versions, so they can work at temperatures of up to 60 degrees Celsius, a temperature that would destroy a natural enzyme.
If the new biomimetic enzyme can be further improved to increase conversion performance, to generate more selective products, it has the potential to increase it on an industrial scale. The technology offers new routes to renewable materials for aviation biofuels and bio-based materials, among other applications.
Research collaboration was facilitated through the WSU-PNNL Bioproducts Institute. Tengyue Jian, Wenchao Yang, Peng Mu, Xin Zhang of PNNL and Yicheng Zhou and Peipei Wang of WSU also contributed to the investigation.
The work was funded by the Joint Center for Aerospace Technology and Innovation in Washington State, a program that supports industry and university research collaborations to develop innovative technologies in the aerospace industry, and by the Department of Energy, Office of Science, Office of Basic Energy. Sciences as part of the Center for the Science of Synthesis Across Scales, an Energy Frontier Research Center located at the University of Washington.
The National Science Foundation (1454575) and the National Institute of Food and Agriculture of the Department of Agriculture provided additional support (2018-67009-27902). Peptoid synthesis capabilities were supported by the Ladder Materials Synthesis and Simulation Initiative, a research and development program led by PNNL laboratories.
Resources
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Jian, T., Zhou, Y., Wang, P. et al. (2022) “Highly stable and adjustable peptoid / hemin enzymatic mimetics with peroxidase – like natural activities”. Common Nat 13, 3025 doi: 10.1038 / s41467-022-30285-9