High Efficiency Rare Earth Element Biomining with Systems Biology Guided Engineering ofGluconobacter oxydans

Abstract

The global demand for critical rare earth elements (REE) is rising with the increase in demand for sustainable energy technologies like wind turbines, electric vehicles, and high efficiency lighting. Current processes for producing REE require high energy inputs and can produce disproportionate amounts of hazardous waste. Biological methods for REE production are a promising solution to this problem. In earlier work we identified the most important genetic mechanisms contributing to the REE-bioleaching capability of Gluconobacter oxydans B58. Here we have targeted two of these mechanisms to generate a high-efficiency bio-mining strain of G. oxydans. Disruption of the phosphate-specific transport system through a clean deletion of pstS constitutively turns on the phosphate starvation response, yielding a much more acidic biolixiviant, and increasing bioleaching by up to 30%. Coupling knockout of pstS with the over-expression of the mgdh membrane-bound glucose dehydrogenase gene, results in up to 73% improvement of REE-bioleaching.

Direct Genome-Scale Screening ofGluconobacter oxydansB58 for Rare Earth Element Bioleaching

“…Even though the increases in Nd-bioleaching created by 9 of the newly identified gene disruptions are large, they are notably smaller than those produced by our current two best-performing strains ( G. oxydans Δ pstS and G. oxydans P112: mgdh , Δ pstS 15 ; demonstrating 322% and 1,186% increase over pWT ( Figure 3 ), and 564% and 1,922% over WT ( Supplementary Figure S1 ).…”

“…The growing demand for an environmentally-friendly supply chain for REE has fueled interest in biotechnological processes for REE mining and recycling 9,[12][13][14][15][16][17][18][19][20] . Bioleaching solubilizes metals from minerals and end-of-life feedstocks with a microbially-secreted mineral-dissolving cocktail called a biolixiviant 13,14,16,[21][22][23] .…”

“…The Generally Regarded As Safe (GRAS) acidophilic bacterium Gluconobacter oxydans [26][27][28][29] has played a significant role in bioleaching research over the past decade 14,21,[30][31][32][33] . This microbe offers a unique capability for secretion of organic acids 21,29,34 and creation of a highly acidic biolixiviant (primarily containing gluconic acid 14 ) which is particularly effective for recovering REE from sources including minerals like allanite 15 ; industrial residues like phosphogypsum 30 , red mud 35 , and blast furnace slag 36 ; and recycled materials like fluid cracking catalyst (FCC) 21 , nickel-metal-hydride (NiMH) batteries 37 , and retorted phosphor powder (RPP) 16,21,35 .…”

“…We have already improved bioleaching of REE by G. oxydans by first identifying genes involved in acid production with high-throughput screening 16 , and then engineering their regulation 15 . We increased REE-bioleaching from the REE-containing mineral allanite by up to 73% by up-regulating the membrane bound dehydrogenase, mgdh , and knocking out the phosphate signaling and transport system pst 15 .…”

Constraints on Lanthanide Separation by Selective Biosorption

“…Significant progress has already been made in developing microorganisms for the first bioleaching step of the biomining process [21][22][23] , and in the second total lanthanide separation step [24][25][26][27][28][29][30][31] . For example, lanmodulin, a lanthanide-binding protein discovered in methylotrophic bacteria, is selective for lanthanides in the presence of molar amounts of competing metal cations 26,30 .…”