(478e) Engineering of Marine Bacteria for Carbon Sequestration By Silicate Rock Weathering

The Earth’s oceans have capacity to permanently sequester >>1000 Gt of anthropogenic CO₂ as bicarbonate ions. The rate of marine carbon sequestration is determined by the dissolution of silicate minerals:

Mg₂SiO₄ + 4H₂O + 4CO₂ --> 2Mg²⁺ + H₄SiO₄ + 4HCO₃^-

Natural rock weathering occurs over geological time scales, however (>10³ years). Enhanced weathering at large scales is precluded, therefore, by the total volume of rock that would have to be simultaneously processed to achieve short-term sequestration targets. Technologies that accelerate the rate of silicate mineral weathering above the basal rate of ~5 µm/year would enable large-scale mineral dissolution processes to capture gigatons of carbon in 10-100 years.

Recently, siderophores were shown to accelerate the dissolution of silicate minerals. These secondary metabolites are produced by microorganisms to harvest insoluble metals such as iron. Siderophores are only produced in iron-limiting conditions, however, which limits their natural abundance and subsequent catalytic effect on mineral weathering.

In this talk, we report engineering of the ubiquitous marine bacterium Alteromonas macleodii for accelerated weathering of the model silicate mineral olivine. We observed that petrobactin, the siderophore naturally produced by A. macleodii, can accelerate olivine dissolution. Then, we used simple genetic engineering tools to upregulate production of petrobactin and observed further acceleration of the mineral weathering rate (Fig 1). Finally, we characterized siderophore-mediated silicate weathering and carbonate sequestration in benchtop chemostats.

This work is the first application of synthetic biology and genome engineering for marine mineral weathering. The platform reported here will enable further optimization of strains for siderophore-mediated mineral dissolution, discovery of additional mechanisms for biological breakdown of silicates, and design of pilot scale mineral bioreactors. In the future, we envision deployment of contained, wastewater-scale, bioreactors for safe, accelerated mineral dissolution and carbon sequestration.