Phd in EARTH SCIENCES

Thesis title: Protection and Consolidation of Stone Heritage: The Role of Carbonatogenic Bacteria

The conservation of stone Heritage is crucial for protecting these materials from various environmental degradation processes over time. This PhD research project explores the innovative use of carbonate-producing bacteria, a technique known as bioconsolidation or biorestoration, as a sustainable alternative to conventional conservation methods for stone materials primarily composed of calcite. Unlike traditional techniques, which can be toxic and face limitations in application, bioconsolidation leverages the natural ability of bacteria to precipitate calcium carbonate, thereby strengthening the stone substrate while respecting the environment. Adopting a multidisciplinary approach, this research integrates microbiological and geological analyses to isolate and characterize microbial species and communities from Cultural Heritage materials and evaluate their biorestoration effectiveness. The study examines the carbonatogenic potential of indigenous bacteria directly sourced from stone artifacts, focusing on their ability to produce calcium carbonate bioprecipitates. The composition, mineralogy, and structure of these microbial precipitates are thoroughly analysed. Selected bacterial strains have been applied to various stone types, including calcarenite (macco), travertine, and marble, to evaluate their effectiveness under different application methods over time. The effectiveness of bioconsolidation has been assessed using various techniques, such as microscopy, spectroscopy, and mechanical testing, to evaluate changes in the physical and chemical properties of the stone materials before and after treatment. These experiments provided comprehensive data on microstructural, mineralogical, and mechanical changes, as well as insights into the compatibility and the effectiveness of the bioconsolidation process. By adapting bioconsolidation techniques to the specific characteristics of each lithology, this research establishes a flexible and effective methodology for the conservation of different stone artefacts. The overall objective is to create a sustainable conservation strategy that minimizes environmental impact while ensuring the preservation of cultural heritage materials for future generations. This innovative approach not only advances conservation practices, but also emphasizes the importance of understanding bacterial-substrate interactions in the development of reliable bioconsolidation strategies.