A September 17, 2025 news item from ScienceDaily announced research from Harvard University focused on more sustainable ways to recycle protein by breaking down keratin,
Key Takeaways
SEAS [School of Engineering and Applied Sciences] researchers have discovered the chemical mechanism by which certain salt compounds break down protein waste, like wool and feathers.
The discovery enables a gentler and more sustainable protein recycling process.
The textile and meat-processing industries produce billions of tons of waste annually in the form of feathers, wool and hair, all of which are rich in keratin – the strong, fibrous protein found in hair, skin and nails.
Turning all that animal waste into useful products – from wound dressings to eco-friendly textiles to health extracts – would be a boon for the environment and for new, sustainable industries. But upcycling proteins is challenging: Breaking down, or de-naturing, proteins into their component parts typically requires corrosive chemicals in large, polluting facilities, keeping any cost-effective protocol out of reach.
Researchers in the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have uncovered key fundamental chemistry of how proteins like keratin de-nature in the presence of certain salt compounds – an insight that could take protein recycling to the next level.
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Caption: An artist’s depiction of hair, made out of keratin, denaturing when ions are present. Credit: Michael Rosnach
A team led by Kit Parker, the Tarr Family Professor of Bioengineering and Applied Physics at SEAS, combined experiments and molecular simulations to better illuminate the chemical mechanisms by which salts cause proteins to unfold. They’ve shown that a solution of concentrated, a salt compound known to break apart keratin, interacts with the protein molecules in a completely unexpected way – not by binding to the proteins directly, as was conventional wisdom, but by changing the structure of the surrounding water molecules to create a setting more favorable for spontaneous protein unfolding.
This insight allowed the researchers to design a gentler, more sustainable keratin extraction process, separating the protein out of solution easily and without the need for harsh chemicals. The process can also be reversed with the same salt mixture, enabling recovery and reuse of lithium bromide denaturants.
The research is published in Nature Communicationsand is also featured in a Behind the Paper blog post.
Inspired by keratin biomaterials
First author Yichong Wang, a graduate student in chemistry who works in Parker’s group, said the research builds on the lab’s longstanding interest in developing keratin biomaterials with shape memory for biomedical applications. They had previously observed that keratin extracted from lithium bromide solvents can form thick, shapeable gels that readily separate from the surrounding solution and solidify almost immediately when placed back in water. While useful, they found the behavior odd, and they wanted to understand it better.
“We thought there might be a gap between current mechanistic understanding of how de-naturation works, and what we were seeing,” Wang said. “That’s when we got very interested in the mechanism itself to see if we could optimize our extraction procedures by explaining this phenomenon better.”
Molecular dynamics reveals shifts in surrounding water
To dig deeper, the team turned to the lab of Professor Eugene Shakhnovich in the Department of Chemistry and Chemical Biology, whose expertise is in protein biophysics. Molecular dynamics simulations led by co-author Junlang Liu allowed them to see that the lithium bromides were not working on the proteins at all, but rather, on the water around them.
It turns out lithium bromide ions cause water molecules to shift into two different populations – normal water, and water molecules that become trapped by the salt ions. As the normal water volume decreases, the proteins start to unfold due to the thermodynamic shift in the environment, rather than being directly ripped apart like in other de-naturation methods. “Making the water less like water, allows the protein to unfold itself,” Wang said. They had similar results by testing simpler proteins like fibronectin, pointing to a universal mechanism.
Better understanding and designing protein extraction methods that are less energy-intensive and less polluting than conventional ones opens potential avenues for protein-upcycling industries. In the Parker lab, using keratin as a substrate for tissue engineering is a major research thrust; having a reliable, sustainable method to extract and re-use such products would bolster their efforts.
What’s more, the process could lay a path for a whole new biomaterials industry, turning a massive waste stream like hair or chicken feathers into low-cost recycled materials, possibly as an alternative for traditional plastics, for example.
The research had many sources of federal support, including the National Institutes of Health (R35GM139571 and R01EY030444) and the National Science Foundation through the Harvard University Materials Research Science and Engineering Center (DMR-2011764). Other funding came from the Health@InnoHK program of the Innovation and Technology Commission, part of the Hong Kong SAR Government; and the Medical and Health Informatics Laboratories at NTT Research, Inc.
Here’s a link to and a citation for the paper,
Entropy-driven denaturation enables sustainable protein regeneration through rapid gel-solid transition by Yichong Wang, Junlang Liu, Michael M. Peters, Ryoma Ishii, Dianzhuo Wang, Sourav Chowdhury, Kevin Kit Parker & Eugene I. Shakhnovich. Nature Communications volume 16, Article number: 6907 (2025) DOI: https://doi.org/10.1038/s41467-025-61959-9 Published online: 26 July 2025 Version of record: 26 July 2025
This paper is open access.
There’s also an August 1, 2025 posting by Yichong Wang and Kit Parker (two of the paper’s authors) on SpringerNature’s Behind the Paper blog,
From Hofmeister’s Curiosity to an Interesting Mechanism
In 1888, Franz Hofmeister published a curious observation: salts affect protein solubility in water in systematic ways. This led to the famous “Hofmeister Series,” a ranking of ions based on their ability to precipitate or solubilize proteins. Over the next century, many studies expanded on these observations of salt-induced effects on protein folding, but a unifying theory explaining how ions influence protein structure remained elusive.
Our recent study originated from a practical challenge rather than a theoretical hypothesis. In our lab’s ongoing work to study the shape memory effect of regenerated keratin — a structural protein abundant in wool, hair, and feathers — we observed some puzzling behaviors. When keratin is extracted using concentrated lithium bromide (LiBr), it does not form a fully solubilized protein solution. Instead, we observed that the proteins spontaneously aggregate into a thick, cohesive gel that can be readily separated from the surrounding solution. More unexpectedly, this protein gel solidifies almost immediately upon rehydration, without the need for dialysis or removal of the denaturants. These phenomenon contrasted sharply with the behavior observed when using organic denaturants such as urea or guanidine hydrochloride.
Illustration by Michael Rosnach (Disease Biophysics Group, Harvard University)
None of these phenomenon matched existing explanations for how LiBr supposedly works. If LiBr denatures proteins by directly binding to them, why would the keratin spontaneously separate out of solution? Why would it renature so quickly just by being placed back in water? …
