Rare earth elements are important for electric vehicles, smartphones, and renewable energy technologies. Despite their benefits, their extraction and processing are associated with significant environmental and health concerns. Over recent years, researchers have explored alternative methods to make mining and refining rare earth metals more sustainable.

Environmental and Economic Challenges

Rare earth elements play a critical role in our modern society, yet their purification is not only environmentally harmful but also economically unviable. Conventional methods of processing these elements involve a traditional thermochemical approach for separating lanthanides.

Since these elements are difficult to refine, they are sent offshore, usually in China, where they will be processed. In 2021, an assessment order by the White House revealed that over-reliance on foreign sources and adversarial nations to process the elements could pose national and economic security.


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Little Bacterium With Big Impact

In a recent study, experts from Cornell University focused on a tiny bacterium called Vibrio natriegens and its role in improving the efficiency of the purification of rare earth elements. This bacterial strain was found to provide a sustainable method known as biosorption, which allows the extraction of elements without using the older, polluting, solvent-heavy approach. The result of their study was described in the paper "Multiple Rounds of In Vivo Random Mutagenesis and Selection in Vibrio natriegens Result in Substantial Increases in REE Binding Capacity."

Led by doctoral students Sean Medin and Anastacia Dressel, the research team genetically engineered the bacterial strain to increase its ability to extract rare earth elements. This was done by changing the genome of Vibrio natriegens with a plasmid called MP6 to introduce errors. After introducing MP6 plasmids, it was confirmed that Vibrio natriegens can still confer an enhanced mutation rate after several rounds of mutagenesis. This is the first work to do this approach to an organism other than Escherichia coli.

This plasmid was used to randomly mutate Vibrio natriegens to achieve over 200% improvement in the biosorption of dysprosium. After the mutant genomes were screened, it was found that genetically engineering the bacterial strain showed only minimal growth defects. Aside from successfully generating biosorption mutants, the researchers also found new genes that were assessed for their role in the observed biosorption changes. They identified 26 genes believed to have a good chance of contributing to the changes.

According to Medin, the results of their work highlight the role of genes in contributing to biosorption, given the ease of finding significant mutants. He also described the power of random mutagenesis in identifying genes under study and optimizing a biological system for a task.

Vibrio natriegens offers a way to safely bring rare earth elements and minerals processing back to the U.S. For instance, biological processing at the Mountain Pass rare earth element mine in California could return the industry to robust domestic productivity. Since this bacterium and similar strains can be engineered without purifying proteins, experts can operate this kind of system more cheaply than other biological processes.

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