Bioconservation of Historic Stone Buildings—An Updated Review

Abstract

Cultural heritage buildings of stone construction require careful restorative actions to maintain them as close to the original condition as possible. This includes consolidation and cleaning of the structure. Traditional consolidants may have poor performance due to structural drawbacks such as low adhesion, poor penetration and flexibility. The requirement for organic consolidants to be dissolved in volatile organic compounds may pose environmental and human health risks. Traditional conservation treatments can be replaced by more environmentally acceptable, biologically-based, measures, including bioconsolidation using whole bacterial cells or cell biomolecules; the latter include plant or microbial biopolymers and bacterial cell walls. Biocleaning can employ microorganisms or their extracted enzymes to remove inorganic and organic surface deposits such as sulfate crusts, animal glues, biofilms and felt tip marker graffiti. This review seeks to provide updated information on the innovative bioconservation treatments that have been or are being developed.

Long-amplicon MinION-based sequencing study in a salt-contaminated twelfth century granite-built chapel

“…The presence of microbes on heritage stonework is generally considered negative owing to the physical and/or chemical damage that they cause via biodeterioration mechanisms. However, the presence of these communities can also have negligible effects, such as surface deposition with no substrate interaction and only an esthetic impact (Sanmartín et al 2020 ), and even positive effects, such as bioprotection, biomineralization, and bio-desalination phenomena (Kembel et al 2014 ; Pinna 2014 ; Gadd 2017 ; Schröer et al 2021 ; Ortega-Morales and Gaylarde 2021 ; Bosch-Roig et al 2021 ). As geomicrobial agents on the built environment, stone colonizers are involved in elemental cycling, rock transformation, soil formation, organic matter decomposition, and cycling of elements, among other processes (Barton and Northup 2007 ; Gadd 2017 ) .…”

Self-Healing of Cementitious Materials via Bacteria: A Theoretical Study

“…The ability of a large community of bacteria to transform a suitable nutrient source into insoluble calcite crystallites-known as microbially induced calcium carbonate precipitation (MICP)-has been used as a part of biotechnologies representing an alternative to traditionally applied methods. Among others, MICP is exploited in dentistry [1], soil bioconsolidation [2][3][4], grouting technologies [5,6], water remediation [7,8], conservation of stone artworks [9,10], and, in particular, civil engineering [11][12][13][14][15]. The formation of calcium carbonate (CaCO 3 ) requires the presence of sufficiently high concentrations of calcium cations (Ca 2+ ) and carbonate anions with a saturation level greater > 1 [16].…”

Study of the Behavior of Structural Materials Treated with Bioconsolidant

“…The authors of [1] show that processes of microbial-induced calcium carbonate precipitation can be used for the production of multifunctional materials but also for permeability and strengthening the loosely cemented layers, consolidation of particles. A complete description of sustainable conservation and, in particular, of biotechnology applied to the preservation of cultural heritage is shown in the work of [3]. The use of microorganisms offers both opportunities and challenges and the potential of microorganism's pro-and against-deterioration of cultural materials (e.g., stones, metals, graphic documents, textiles, paintings) [3][4][5].…”

“…A complete description of sustainable conservation and, in particular, of biotechnology applied to the preservation of cultural heritage is shown in the work of [3]. The use of microorganisms offers both opportunities and challenges and the potential of microorganism's pro-and against-deterioration of cultural materials (e.g., stones, metals, graphic documents, textiles, paintings) [3][4][5].…”

“…** X is the number of the specimen(1,2,3). *** Untreated specimen to control the characteristics at the same fabrication age of treated specimens.…”