Application of Microbial Biotechnology in Conservation and Restoration of Stone Monument

Abstract

Treatments employed for the consolidation of monumental stones made of limestone due to incompatibility from the substrate and cement used for consolidation, plugging of pores induced by the new cement, leading to the acceleration of stone alteration. Microbial precipitation with a layer of calcium carbonate generated by bacteria might offer a solution to this dilemma because the layer would not block the natural pore structure, thus permitting free passage of soluble salts through the stone. In this study, an attempt has been made to provide an overview of the microbial induced carbonate precipitation as promising technology for bioremediation of such structures. At the first, the active microorganisms in the conservation of stone monuments transferred to the laboratory using the swap dipped in nutrient broth at a historic cemetery. After incubation and growth of colonies, Gram-positive bacilli were detected. Then pure single colonies were transferred to blood agar medium and incubated at 37°C. The single colonies were transferred to the surface of sterilize limestone pieces and incubated but no result was obtained. Therefore, in the next phase bacilli bacteria-rich broth media was used. The control experiments were conducted in accordance with the conditions mentioned without bacterial inoculation. The calcification process caused by the inoculated bacteria on the historical stone samples was demonstrated using the scanning electron photomicrographs. Microbially induced calcium carbonate precipitation (MICP) technology to eco–friendly, self-healing and highly durable nature of these bio-binders, for conservation purposes has been found suitable. But still there has been much to explore in order to bring this environmentally safe, cost effective and convenient technology from lab to field scales.