Biometallurgy

Microbial recovery of critical metals from electronic waste

Methylotrophic bacteria have the innate ability to selectively extract insoluble rare earth elements (REEs) from the environment by secreting REE-binding ligands (lanthanophores) and transporting them into the cell for use in alcohol metabolism via the alcohol dehydrogenases XoxF and ExaF. By leveraging the power of genetics, RNAseq transcriptomics, metabolomics, directed evolution, we are unraveling the REE metabolic network, from extracellular solubilization to intracellular biomineralization. REEs are critical components of many clean energy and consumer technologies. Global demand for REEs is at an unprecedented high, but the supply chain is vulnerable. Chemical methods for extraction of REE from raw materials are energy intensive and environmentally destructive, necessitating the development and commercialization of green REE recovery technologies. By incorporating our discoveries in REE biochemistry with genetic engineering, we are developing a highly selective, environmentally friendly bacterial platform for the recovery of REE from waste products such as complex electronic waste. We are excited to announce the technology was recently spun-out into the startup, RareTerra, co-founded by myself and Dr. Martinez Gomez.

Figure 1. Recovery of rare earth elements (REEs) from various sources, including ores, magnet swarf, and electronic waste.

Team members & Collaborators

NATHAN GOOD
Senior Project Scientist

MORGAN SU
Research Technician

BETSY SKOVRAN
Professor, SDSU

DAN PARK
LLNL

HONGYUE JIN
Professor, University of Arizona

Lanthanide solubilization and Chelation

While lanthanide-dependent metabolism is widespread in nature and has been proven to drive one-carbon metabolism in bacteria, details about the machinery necessary to sense, sequester, and traffic lanthanides (Ln) remain unknown. We have identified and characterized the first known Ln-chelator biosynthetic gene cluster, encoded by META1p4129 through META1p4138, that we named the Lanthanide Chelation Cluster (LCC). The LCC encodes a TonB dependent receptor and NRPS biosynthetic enzymes and is predicted to produce a metal-chelating molecule.

The LCC was highly upregulated when M. extorquens AM1 was grown using Nd₂O₃ and expression in trans enabled an increase of Nd bioaccumulation by over 50%. Expression of the LCC in trans did not affect iron bioaccumulation, providing further evidence that its product is a novel Ln-chelator. Finally, expression of the LCC in trans increased Nd, dysprosium (Dy), and praseodymium (Pr) bioaccumulation from the complex Ln source NdFeB magnet swarf by over 60%, opening new strategies for sustainable recovery of these critical Rare Earth Elements.

Team members & Collaborators

ALEXA ZYTNICK
UC Berkeley Ph.D Candidate

TRINITY REIMER
UC Berkeley Undergraduate

LENA DAUMANN
Professor, LMU München

ALLEGRA AARON
Professor, University of Denver

ZACHARY REITZ
UCSB Ph.D Candidate

Phage-Bacterial Hybrid Metallurgy

We are currently investigating the machinery that M. extorquens uses for growth with lanthanides in mineral form (poly-phosphate and ores), in order to develop a cost-effective and environmentally-friendly bioprocess for extraction and separation of lanthanides. In collaboration with the lab of Dr. Seung-Wuk Lee in the Department of Bioengineering at UCB, we are developing a novel bio-hydrometallurgical process that integrates bacterial chelation and sequestration of lanthanides with engineered lanthanide-binding bacteriophage (phage) to selectively bioleach and separate lanthanides from mixed insoluble substrates such as ores.

Team members & Collaborators

MONICA CESINGER
Postdoctorate Fellow

KIRTY WADHAWAN
Research Technician

SEUNG-WUK LEE
Professor, UC Berkeley

Gadolinium Recovery from Clinical Waste and Waste Water

Mesophilic methylotrophic bacteria like M. extorquens AM1 are naturally able to acquire lanthanides (part of the rare earth elements) from their environment. Biologically available lanthanides are limited to the “light” members of the series, lanthanum through samarium (atomic numbers 57-62). Using directed evolution, we isolated a genetic variant capable of growth using the “heavy” lanthanide, gadolinium (Gd, atomic number 64). This variant of Methylobacterium has increased heavy lanthanide storage by more than 80-fold and grows robustly on methanol.

Gd is used heavily as a contrast agent for magnetic resonance imaging (MRI) because of its unparalleled paramagnetic properties. In free form, however, Gd is acutely toxic to humans. Rising Gd concentrations in surface water correlates with increasing annual MRI exams, raising concerns that unmetabolized contrast agents, excreted in the urine, are contaminating water streams. There is currently no effective method to recycle Gd from medical waste or contaminated water. Our variant M. extorquens AM1 strain can efficiently sequester Gd from common MRI contrast agents, and therefore is a promising bioremediation agent. We are studying the unique physiological properties of this strain to further increase Gd acquisition in development of a microbial platform to recycle Gd and reduce groundwater contamination.