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Researchers genetically engineered the metabolic pathways in yeast to produce oxalic acid, which can be used to extract free rare earth elements from low-grade ore.
Graphic Credit: Courtesy Dan Herchek/LLNL
Scientific Frontline: Extended "At a Glance" Summary: Engineered Yeast for Rare Earth Element Recovery
The Core Concept: A novel, environmentally sustainable biomanufacturing process that utilizes genetically engineered yeast to produce oxalic acid, which is subsequently used to extract and purify free rare-earth elements (REEs) from low-grade ore.
Key Distinction/Mechanism: Conventional oxalic acid production relies on strong acids and generates environmentally hazardous byproducts. In contrast, this new method employs a low-pH-tolerant yeast strain (Issatchenkia orientalis) with modified metabolic pathways to convert glucose directly into oxalic acid. The resulting fermentation broth acts as an oxidizer that selectively binds to REEs, precipitating them into a solid state with over 99% efficiency while leaving unwanted "junk" metals (like zinc) dissolved in solution.
Origin/History: It was developed through a collaboration between the University of Illinois Urbana-Champaign, Lawrence Livermore National Laboratory (LLNL), and the University of Kentucky, in response to a Defense Advanced Research Projects Agency (DARPA) solicitation aimed at utilizing environmental microbes as bioengineering resources.
Major Frameworks/Components:
- Metabolic Engineering: The genetic alteration of Issatchenkia orientalis to optimize the biological conversion of sugars into high yields of oxalic acid (achieving over 40 grams per liter).
- Selective Precipitation: The chemical mechanism by which bio-produced oxalic acid isolates REEs from mixed-metal ore solutions under realistic processing conditions.
- Integrated Process Engineering: The end-to-end combination of synthetic biology and chemical processing to create a unified workflow from microbial fermentation to materials recovery.
Branch of Science: Synthetic Biology, Chemical and Biomolecular Engineering, Materials Science, and Environmental Science.
Future Application: The development of scalable, domestic industrial flowsheets for REE purification to support the manufacturing of consumer electronics, clean energy infrastructure, defense systems, and biomedical imaging technology. Ongoing research is focused on increasing the acid-to-sugar yield to maximize commercial viability.
Why It Matters: The global market for both REEs and oxalic acid is currently dominated by foreign supply chains, often requiring months to fulfill orders. This bio-engineered approach circumvents long-standing supply-chain vulnerabilities by providing the United States with an economically viable, domestic, and ecologically responsible method for securing critical minerals.
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| From left to right: Shih-I (Harry) Tan, Huimin Zhao, Zhixin Zhu, Jingxia Liu, Wenjun Guo, Jeremy Guest, Sarang Bhagwat. Photo Credit: Julia Pollack |
There is a new, U.S.-based, environmentally friendly method for mining rare-earth elements used in consumer electronics, clean energy, defense and biomedical imaging. By using oxalic acid made by sugar-eating engineered yeast, the new technique can extract almost all the rare-earth elements from low-grade ore.
China currently dominates the market in both REE and oxalic acid, and orders for the conventionally produced acid can take up to six months to be fulfilled. In response to a Defense Advanced Research Projects Agency Environmental Microbes as a Bioengineering Resource solicitation, a team at Lawrence Livermore National Laboratory identified this bottleneck and discussed it with colleagues at the University of Illinois Urbana-Champaign — who have been working with engineered yeast strains to produce similar products for years — to explore potential U.S.-based bioengineered alternatives.
Additionally, conventional methods for producing oxalic acid employ other strong acids during processing, thereby generating byproducts that pose environmental challenges. “Our bio-engineered process uses the oxidizer produced from glucose, directly from the yeast organism,” said Jingxia Lu, a postdoctoral researcher at Illinois and study co-author.
The new proof-of-concept study, led by scientists from the U. of I., LLNL, and the University of Kentucky, uses the yeastIssatchenkia orientalis to produce oxalic acid and to leach REE from ore.
“Biomanufacturing oxalic acid by engineering the low-pH-tolerant yeast Issatchenkia orientalis greatly simplifies the process, making the entire REE recovery process potentially economically viable,” said Huimin Zhao, a professor of chemical and biomolecular engineering at the U. of I. “By leveraging our expertise in metabolic engineering of this low-pH-tolerant yeast for organic acid production, we were able to quickly create a yeast strain capable of producing more than 40 grams per liter of oxalic acid and use the fermentation broth directly for rare earth element precipitation with over 99% efficiency.”
Oxalic acid binds to rare-earth elements and selectively transforms them from a solution to a solid. In doing so, it separates them from other “junk” metals like zinc, which stay dissolved in the solution.
“What’s especially powerful about this approach is that it turns a long-standing supply-chain vulnerability into a domestic biomanufacturing opportunity,” said Yongqin Jiao at LLNL. “By coupling low-pH yeast bioproduction with selective rare earth precipitation, this work points to a scalable, sustainable pathway for REE purification.”
The team verified this process using real-world ore samples provided by the University of Kentucky and lab analyses performed at Kentucky and the U. of I.
“This step provides a crucial validation of bio-oxalic acid under realistic ore-processing conditions and establishes a strong foundation for its integration into industrial rare earth extraction and purification flowsheets,” said Rick Honaker of the University of Kentucky.
Although the researchers have demonstrated that their bio-oxalic acid is highly effective at selectively separating REE from ore, they acknowledge that the new process currently yields only a small amount of acid relative to the sugar it consumes. To make the entire process more commercially viable, the yield will need to increase. The team is currently working on improvements to do so.
“This work is a great example of what becomes possible when synthetic biology and chemical process engineering are tightly integrated,” said Dan Park at LLNL. “Illinois’ metabolic engineering expertise and LLNL’s rare earth separation and validation capabilities came together as a truly multidisciplinary team, enabling an end-to-end solution — from biological production to materials recovery.”
Funding: The DARPA Environmental Microbes as a Bioengineering Resource program supported this research.
Published in journal: Nature Communications
Title: Bio-based oxalic acid production in Issatchenkia orientalis enables sustainable rare earth recovery
Authors: Jingxia Lu, Wenjun Guo, Ziye Dong, Sarang S. Bhagwat, Shih-I Tan, Zhixin Zhu, Andrew Johnson, Jeremy S. Guest, Rick Honaker, Dan M. Park, Yongqin Jiao, and Huimin Zhao
Source/Credit: University of Illinois Urbana-Champaign | Lois Yoksoulian
Reference Number: beng031626_01