The use of microorganisms for the removal of sulphates on artistic stoneworks

Bacterial carbonate precipitation is known to be a natural phenomenon associated with a wide range of bacterial species. Recently, the ability of bacteria to produce carbonates has been studied for its value in the conservation of limestone monuments and concrete. This paper describes investigations of carbonate crystals precipitated by freshwater bacteria by means of histological (Loeffler's methylene blue and alcian blue-periodic acid-Schiff stain) and fluorescence (CTC [5-cyano-2,3-ditolyl tetrazolium chloride]) stains, determination of cell viability inside carbonate crystals, and pore size reduction in limestone by image analysis. Carbonate crystals were found to be composed of bacteria embedded in a matrix of neutral and acid polysaccharides. Cell viability inside the carbonate crystals decreased with time. On stone, bacteria were found to form carbonate crystals, with only a few bacteria remaining as isolated cells or as cell aggregates. Pore size was reduced by about 50%, but no blockage was detected. Taken together, the results of this research provide some reassurance to conservators that biocalcification by bacteria could be a safe consolidation tool in a restoration strategy for building stone conservation.

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“…However, the controlled action of bacteria has been demonstrated to be potentially useful in the restoration of art works (14,33,44,45,46,47).…”

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confidence: 99%

Carbonate Crystals Precipitated by Freshwater Bacteria and Their Use as a Limestone Consolidant

Zamarreno

Inkpen

May

2009

Appl Environ Microbiol

118

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“…However, it has been recently seen that they can be used for the removal of harmful compounds on artistic objects (5,12,14).…”

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confidence: 99%

“…Later, Ranalli et al (12) employed D. desulfuricans and Desulfovibrio vulgaris on two objects, an old marble "horse hoof" and an old marble column. As an improvement over the previous method, the authors used the inorganic material sepiolite as a delivery system.…”

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confidence: 99%

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Improved Methodology for Bioremoval of Black Crusts on Historical Stone Artworks by Use of Sulfate-Reducing Bacteria

Cappitelli

Zanardini

Ranalli

et al. 2006

Appl Environ Microbiol

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An improved methodology to remove black crusts from stone by using Desulfovibrio vulgaris subsp. vulgaris ATCC 29579, a sulfate-reducing bacterium, is presented. The strain removed 98% of the sulfates of the crust in a 45-h treatment. Precipitation of black iron sulfide was avoided using filtration of a medium devoid of iron. Among three cell carriers, Carbogel proved to be superior to both sepiolite and Hydrobiogel-97, as it allowed an easy application of the bacteria, kept the system in a state where microbial activity was maintained, and allowed easy removal of the cells after the treatment.

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“…Various carrier materials were looked upon. Ranalli et al (1997) used sepiolite for delivering Desulfovibrio vulgaris and D. desulfuricans as it provided anaerobic conditions, humidity and shortened treatment time. Capitelli et al (2006) reported the superiority of Carbogel as a delivery system for bacteria because of higher retention of viable bacteria and less time needed for entrapment of cells by this.…”

Section: Reduction In Permeation Of Stone By Microbial Concretementioning

confidence: 99%