Abstract
Biomineralization is a natural process that transforms inorganic precursors to mineralized products. With applications to materials synthesis and mineral extraction, biomineralization is a green alternative to traditional wet chemistry and hydrometallurgical techniques. In these traditional approaches, organic solvents, high temperatures, and hazardous wastes are ubiquitous, but via biomineralization the same results can be achieved at room temperature in aqueous conditions. In this work, I probe the structure and function of precision biomineralization protein silicatein for applications in inorganic oxide nanoparticle synthesis. While silicatein produces monodisperse, crystalline particles, the rate of production is not competitive with current wet chemistry techniques. Therefore, enzyme solubility and kinetics are targeted via the addition of fusion tags, directed evolution, and rationale-based design.
Further, I examine the robust biomineralization protein smCSE as a tool for rare earth element (REE) extraction. Crystallography of smCSE with metal precursor reveals a probable metal-interaction site, which I probe via site-directed mutagenesis, followed by evaluation of biomineralization with REEs and targeted end use with simulated waste streams.
While biomineralization is promising for materials synthesis applications, it may also be a valuable tool for critical mineral extraction. Accordingly, I consider the harsh conditions associated with mining REEs in order to identify promising new biomineralization actors. Collection and culture of microbial species identified from mines in southwestern Virginia, followed by screening for tolerance and degradation of bituminous compounds and metals reveals Lysinibacillus sphaericus. In regards to bitumen degradation, L. sphaericus degrades polycyclic aromatic hydrocarbons anthracene and naphthalene in minimal media. Moreover, L. sphaericus also shows biomineralization of saline lithium chloride to lithium hydroxide nanoparticles, which may be promising as a critical mineral extraction technique.
Finally, in collaboration with researchers at the United States Air Force Academy, this work implements silicatein in cyanobacteria for a carbon-negative biomanufacturing approach and applies silicatein biosilicification for biocementation in austere environments. These applications highlight the versatility and wide applicability of biomineralization.
Overall, this work highlights structure and function of biomineralization proteins with applications in materials synthesis and mineral extraction.
