Biomineralization of calcium carbonate by marine bacterial strains isolated from calcareous deposits

Biomineralization induced by microbial enzymes, which catalyse CaCO3 precipitation, is a promising field of research for various applications in building eco-materials. Especially, this could provide an eco-friendly process for protection of coastal areas against erosion. In the present investigation, fourteen bacterial strains were isolated and characterized from both natural seawater and calcareous deposits formed on a cathodically protected steel mesh in marine environment. All of them induced calcium carbonate precipitation in various media by producing urease and/or carbonic anhydrase enzymes. The calcium carbonate minerals produced by bacteria were identified by microscopy and µ-Raman spectroscopy. In parallel, an experimental set-up, based on a column reactor, was developed to study biomineralization and microbial capacity of Sporosarcina pasteurii to form sandy agglomerate. These well-known calcifying bacteria degraded the urea present in liquid medium circulating through the column to produce calcium carbonate, which acted as cement between sand particles. The bio-bricks obtained after 3 weeks had a compressive strength of 4.2 MPa. 20% of the inter-granular voids were filled by calcite and corresponded to 13% of the total mass. We successfully showed that bio-column system can be used to evaluate the bacterial ability to agglomerate a sandy matrix with CaCO3.