Steering biomineral crystallization by tailor-made media composition for stone conservation

Microorganisms are capable to attach to rock surfaces and live inside porous systems. In the context of stone conservation, bacteria presence, and their metabolites might positively influence stones’ durability. Through phenomena such as bioclogging, biocement, and biogas production, the pore scale environment could be altered (1)(2). These alterations might influence the weathering development internally in the stones. In order to make these alterations being beneficial in the context of preservation of cultural heritage, the microbial activity inside the rock needs to be regulated. In this study, a bacterial denitrification metabolism will be engineered for creating the three phenomena. An obvious approach to direct the activity of denitrifiers with respect to bioclogging as well as biocement and biogas production is to manipulate the surrounding solution. For this, we are developing a quantitative model for predicting the production of biomass, gas and biocement based on the initial composition of the applied medium. Here, formation of biocement can be achieved through microbial induced calcite precipitation (MICP) due to the effects of denitrification on the amount and speciation of dissolved carbonate (3). The model will be parameterized and validated based on batch experiments. The results of the model will be used to identify optimal media compositions to induce the process to a desired extent inside the stone network. Hence, the model will create the basis to investigate in the future the consequences of microbially mediated reactions in the rock on water flow and, ultimately, stone conservation.