Microbial biotechnologies to preserve and restore stone monuments

The role of microbes as decaying promoters of stone surfaces and of environmental factors they control has been established since long time. On the contrary, the positive effects of microbial interventions on the stone surface preservation and restoration has deserved, so far, much less attention. The present work describes calcite precipitation by bacterial strains isolated from carbonate rich environments. Also, this study investigates the potential relationship between extracellular polymeric materials (EPM) - such as exopolysaccharides (EPS) and capsular polysaccharides (CPS) isolated from calcifying bacteria -and calcium carbonate crystals precipitation. The ability to form CaCO3 crystals, the extent of the precipitation, and the type of crystals formed are influenced by temperature as well as by microbial cellsgrowth. Shapes and dimensions of the crystals depend on both bacterial strain and its growth conditions. Further researches are in progress directly aiming to develop biotechnological processes by which stone decaying surfaces are restored by EPM or by isolated protein produced from them.