title: Biocalcifying Bacillus subtilis cells effectively consolidate deteriorated Globigerina limestone.
abstract: Microbially induced calcite precipitation occurs naturally on ancient limestone surfaces in Maltese hypogea. We exploited this phenomenon and treated deteriorated limestone with biocalcifying bacteria. The limestone was subjected to various mechanical and physical tests to present a statistically robust data set to prove that treatment was indeed effective. Bacillus subtilis conferred uniform bioconsolidation to a depth of 30 mm. Drilling resistance values were similar to those obtained for freshly quarried limestone (9 N) and increased up to 15 N. Treatment resulted in a high resistance to salt deterioration and a slow rate of water absorption. The overall percentage porosity of treated limestone varied by ±6 %, thus the pore network was preserved. We report an eco-friendly treatment that closely resembles the mineral composition of limestone and that penetrates into the porous structure without affecting the limestones' natural properties. The treatment is of industrial relevance since it compares well with stone consolidants available commercially.
authors.affiliation: Department of Physiology and Biochemistry, Faculty of Medicine, University of Malta, Msida, Malta.|Department of Chemistry, Faculty of Science, University of Malta, Msida, Malta.
authors.forename: Roderick
authors.initials: R
authors.lastname: Micallef
authors.affiliation: Department of Metallurgy and Materials Engineering, Faculty of Engineering, University of Malta, Msida, Malta.
authors.forename: Daniel
authors.initials: D
authors.lastname: Vella
authors.affiliation: Department of Chemistry, Faculty of Science, University of Malta, Msida, Malta.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Sinagra
authors.affiliation: Department of Physiology and Biochemistry, Faculty of Medicine, University of Malta, Msida, Malta. gabrielle.zammit@gmail.com.
authors.forename: Gabrielle
authors.initials: G
authors.lastname: Zammit
mesh_terms: D001406:Bacillaceae / Q000378:metabolism; D001412:Bacillus subtilis / Q000378:metabolism*; D002119:Calcium Carbonate / Q000378:metabolism*; D003470:Culture Media; D058641:Planococcaceae / Q000378:metabolism; D058644:Sporosarcina / Q000378:metabolism; D014867:Water / Q000737:chemistry
chemical_list: D003470:Culture Media; D014867:Water; D002119:Calcium Carbonate
keywords: Bacillus subtilis; Biocalcification; Bioconsolidation; Calcite; Limestone