What if the waste we flush away every day could become a building block for repairing bones, restoring ancient artifacts, or even replacing plastic? That’s the surprising reality behind a new discovery from a global team of scientists, including materials science professor David Kisailus of the University of California, Irvine.

In a study recently published in Nature Communications, the researchers revealed an innovative process that uses a genetically engineered yeast – charmingly dubbed “osteoyeast” – to turn human urine into hydroxyapatite, a mineral prized for its role in medical implants and other high-value products.

“This process achieves two goals at the same time,” said co-author David Kisailus, UC Irvine professor of materials science and engineering. “On the one hand, it helps remove human urine from wastewater streams, mitigating environmental pollution and the buildup of unwanted nutrients; and on the other hand, it produces a material that can be commercially marketed for use in a variety of settings.”

The research was supported by the U.S. Department of Energy, DARPA and the Air Force Office of Scientific Research — agencies that see potential in using biology to create sustainable, high-performance materials.

Urine: From Problem to Possibility

Human urine contains high levels of nutrients, especially nitrogen and phosphorus, which can pollute waterways and harm ecosystems if not properly treated. But it also contains key ingredients for hydroxyapatite (HAp), a naturally occurring calcium phosphate that makes up the hard part of our bones and teeth.

Traditionally, producing HAp on an industrial scale has been expensive and environmentally taxing. That’s where the scientists’ “osteoyeast” comes in.

Inspired by the way mammalian bone cells (osteoblasts) form hydroxyapatite inside the body, the team designed yeast cells that mimic this process. These modified microbes break down urea in urine, raise the surrounding pH, and then absorb calcium and phosphate. Within hours, the yeast secretes and crystallizes hydroxyapatite — transforming a problematic waste product into something incredibly useful.

The results are promising: the team was able to produce one gram of hydroxyapatite per liter of urine in less than a day.

Fermentation Meets Innovation

Best of all, the process is simple and scalable.

“The fact that it uses yeast as a chassis, which is inexpensive and can be placed in large vats at relatively low temperatures – think about beer that’s made via fermentation processes and is well scaled – shows that this can be done easily without major infrastructural needs, and that has the added benefit of making it accessible to developing economies,” Kisailus says.

Kisailus, who specializes in how materials grow and crystallize in nature, contributed by analyzing how the yeast platform forms HAp crystals. Now, he’s teaming up with fellow researcher Yasuo Yoshikuni from Lawrence Berkeley National Laboratory to explore how the yeast system might be adapted to produce materials for energy and even 3D-printed structures.

A Future Built on Bio-Based Materials

Hydroxyapatite is already used in bone grafts and dental fillings, but synthetic versions are expensive to manufacture. This yeast-based method could offer a cleaner, cheaper, and more eco-friendly alternative — not just for medicine, but also for replacing plastics in building materials and other products.

For Kisailus, this is more than just a scientific breakthrough. It’s a vision of a future where waste isn’t wasted — and where biology and engineering come together to build a more sustainable world.

This feature was generated by Chat GPT from a UC Irvine-issued press release. The images are original.

About the University of California, Irvine: Founded in 1965, UC Irvine is a member of the prestigious Association of American Universities and is ranked among the nation’s top 10 public universities by U.S. News & World Report. The campus has produced five Nobel laureates and is known for its academic achievement, premier research, innovation and anteater mascot. Led by Chancellor Howard Gillman, UC Irvine has more than 36,000 students and offers 224 degree programs. It’s located in one of the world’s safest and most economically vibrant communities and is Orange County’s second-largest employer, contributing $7 billion annually to the local economy and $8 billion statewide. For more on UC Irvine, visit www.uci.edu.

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About UC Irvine’s Brilliant Future campaign: Publicly launched on Oct. 4, 2019, the Brilliant Future campaign aims to raise awareness and support for the university. By engaging 75,000 alumni and garnering $2 billion in philanthropic investment, UC Irvine seeks to reach new heights of excellence in student success, health and wellness, research and more. The Samueli School of Engineering plays a vital role in the success of the campaign. Learn more by visiting https://brilliantfuture.UC Irvine.edu/the-henry-samueli-school-of-engineering.