The next time someone tells you that you are “throwing away” something precious, you might reply that in fact that is exactly what you do every day when you go to the bathroom. A finding just published in Nature Communications. has shown that human urine contains everything needed to produce hydroxyapatite, the material that bones and teeth are made of.
The key lies in an engineered yeast called “Osteoyeast,” which Berkeley Lab researchers have programmed to turn into a biological factory for biomedical materials.
Yeast that mimics bone cells
The project was born from the observation of Yasuo Yoshikuni e Peter Ercius, researchers at the Lawrence Berkeley National Laboratory, who noted how the Saccharomyces boulardii (a yeast similar to that used to make beer) already possessed molecular mechanisms surprisingly similar to osteoblasts, the cells specialized in bone formation.
“The fortuitous part is that this yeast already had similar molecular mechanisms,” he explained. Yoshikuni of Published Research. “It only took a few small changes to convert yeast into a cellular factory for hydroxyapatite.”
The researchers added just two genes: one for an enzyme that breaks down urea and one for a urea transporter. When yeast breaks down urea from urine, it raises the pH inside the cells, activating a calcium pump that floods the vacuoles with the ingredients to form minerals.
How urine transformation works
Osteoyeasts, as mentioned, use enzymes to break down urea and increase the pH of the surrounding environment. This triggers the accumulation of calcium and phosphate in the form of amorphous calcium phosphate in the yeast vacuoles, which is then secreted into vesicles and crystallized into hydroxyapatite.
David Kisailus, professor of materials science and engineering at the University of California Irvine, stressed how this process takes less than a day to produce hydroxyapatite.
“The fact that it uses yeast as a chassis, which is cheap and can be placed in large vats at relatively low temperatures, shows that it can be done easily without major infrastructure needs.”
The Numbers That Count in Urine
The economic results are impressive. The techno-economic analysis conducted by JeremyGuest of the University of Illinois has shown that The process could cost about $19 to produce a kilogram of commercial-quality hydroxyapatite, which can be sold for $50-200 .
The system could generate a profit of about $1,4 million per year serving a city the size of San Francisco, while simultaneously reducing the chemical inputs needed to make wastewater safe. How explained by Guest, “It is important to consider the potential impacts of a large-scale system.”
Applications beyond hydroxyapatite from urine
Urine is just the beginning. The team is already working to develop new strains that can synthesize other biomaterials or capture and store specific elements to enable environmentally sustainable biomining operations.
“Today, we use about 1 percent of the world’s energy to produce fertilizer from nitrogen gas,” Yoshikuni said. “If we could produce both hydroxyapatite and nitrogen fertilizer from ammonia, we could potentially replace a significant portion of the total demand for nitrogen.”
The osteoyeast patent is now available for licensing, potentially opening up new avenues for the sustainable production of biomaterials from human waste streams. How highlighted by researchers, biotechnology continues to demonstrate its potential to transform waste materials into valuable resources.
A discovery that demonstrates how the circular economy can really start from the bathroom at home.
