Sublimestone

The Mission

Creating a dual-microbial system to fix micro-cracks in limestone buildings.

The challenge

As Sublimestone we put our main focus on the limestone buildings, which are an integral part of our cultural heritage - especially in Maastricht. Unfortunately, as a carbonate sedimentary rock, limestone is particularly affected by the processes of weathering and erosion. With the escalation of climate change, this natural deterioration has been accelerated, owing mainly to the detrimental impacts of acid rain, elongated rain seasons, and air pollutants. All of these factors contribute to the formation of microcracks within the buildings. Currently, crack healing systems for limestone restoration present various challenges. Common physical and chemical procedures used are labor-intensive and expensive. Therefore it is important to address and fix those structural impurities before escalation.

The solution

Our solution is to engineer bacteria capable of promoting the restoration of cracks in limestone. To achieve this, we use a two-phase system involving the engineering of two distinct strains of E. coli specifically designed to address these cracks. The first strain produces single-stranded DNA, which self-assemble through complementary base pairing into robust DNA origami octahedron nanostructures, providing a scaffold within the crack. The second strain displays carbonic anhydrase on the surface of our E. coli, which will increase its enzymatic activity. By utilizing CO2 and Ca+, the enzyme enables the production of calcium carbonate, ultimately leading to calcite deposition. Importantly, the carbonic anhydrase enzyme operates without generating any toxic byproducts, and it even contributes to the sequestration of CO2. The calcite then precipitates along the negative phosphate backbone of the DNA origami scaffold, which acts as a strong nucleation site, facilitating the mineralization of calcite. The resulting calcite crystals improve the limestone's structural stability, providing a protective layer and effectively repairing cracks. We believe we could implement this technology for other materials in the future. Our highly programmable DNA structure can be adapted to numerous structures, expanding the use of our engineered bacteria. Additionally, our work has the potential to contribute to other scientific fields such as medicine, including bone regeneration and drug delivery.