Developing a 'natural antifreeze' to prevent freezer burn

Engineers at the University of Utah’s John and Marcia Price College of Engineering have turned to nature for inspiration to develop a synthesised protein that could be used to prevent food and drugs from freezing.

Fish that inhabit polar waters have proteins in their blood that prevent it from freezing. The stripped-down version of glycoproteins in polar-region fish is simple enough to be manufactured at scale, but powerful enough to inhibit formation of ice crystals at sub-zero temperatures without toxicity of chemical antifreeze.

The researchers demonstrated the effectiveness of their mimic polypeptides on several real-world test cases, including ice cream and an anti-cancer drug. The former was successfully chilled down to -20°C (-4°F), while the latter survived temperatures as low as -197°C (-323°F).

The study, funded by the National Science Foundation, was published in the journal Advanced Materials. It was led by Jessica Kramer, an associate professor in the Department of Biomedical Engineering, and Thomas McParlton, a graduate student in her lab.

For decades, researchers have eyed the naturally occurring antifreeze proteins found in certain polar fish, as well as some insects and plants. However, extracting meaningful quantities of these proteins from living organisms is impractical for commercial use. They are also susceptible to contamination with allergens.

Kramer and her colleagues therefore set out to determine the exact physical and chemical properties of these proteins that were responsible for their antifreeze capabilities. A pair of earlier studies, published in Chemistry of Materials and Biomacromolecules, demonstrated the structural features that were most critical in the naturally occurring proteins.

“Ultimately, we simplified the structure to only the parts we thought were required for antifreeze activity, which makes production less complicated and expensive,” Kramer said. “Despite those changes, this study showed that our mimics bind to the surface of ice crystals and inhibit crystal growth, just like natural antifreeze proteins.”

“Best of all,” McParlton said, “we make these mimics entirely using chemistry — no fish or cells required.”

As proof of concept, the researchers demonstrated that the mimic molecules are non-toxic to human cells, are digestible by enzymes of the human gut, and can survive heating, a critical factor for its potential for food production. They also ran tests on sensitive enzymes and antibodies, showing that the mimics protected them from damage associated with freeze/thaw cycles.

“We also showed that we can inhibit ice crystals in ice cream, which often happens during shipping or when people take the carton in and out of the freezer,” Kramer said.

The researchers envision their mimic molecules enabling a wide variety of applications, from extending the shelf life of frozen foods to improving the storage and transport of life-saving biologics. The technology is currently patent pending, and the team is working to bring their innovation to market through a new startup company, Lontra Bio LLC, which aims to commercialise these synthetic antifreeze proteins.

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