High efficiency rare earth element bioleaching with systems biology guided engineering of Gluconobacter oxydans
Alexa M. Schmitz, Brooke Pian, Sabrina Marecos, Mingming Wu, Megan Holycross, Esteban Gazel, Matthew C. Reid, Buz Barstow
Abstract
Biological methods are a promising route for the environmentally-friendly production of rare earth elements (REE), which are essential for sustainable energy and defense technologies. In earlier work we identified the key 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 bioleaching 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 using the P112 promoter (strain G. oxydans ΔpstS, P112:mgdh) reduces biolixiviant pH by 0.39 units; increases REE-bioleaching by 53% at a pulp density of 10% and increases it by 73% at a pulp density of 1%. Using insights from whole-genome screening, the mineral-dissolving microbe Gluconobacter oxydans was engineered by deleting the pstS gene and overexpressing mgdh, creating a strain that improves rare earth element extraction by up to 73%.