REMOVAL FOR COMPLEX SULPHATE BLACK CRUSTS IN A LARGE SCALE BIORESTORATION TREATMENT

In recent years there has been an increasing focus on cultural heritage conservation methods, especially those able to conjugate efficiency, selectivity and safety for the restorer and the environment. Recent improvements in the biotechnologies open interesting prospects for the development of new products based on live microorganisms (sulphate- or nitrate- reducing bacteria) used as cleaning agents for the removal of white and black crusts. Despite promising progress, this practice known as biorestoration is still limited to small surface areas. This is mainly because: i) the technique is time-consuming in presence of thick and compact crusts and ii) the production of a large amount of bacterial biomass is often quite expensive. The above mentioned limitations were faced in the study case described here. Bacterial cells of Desulfovibrio vulgaris were produced with an improved production process and successfully applied on a one-century-old marble statue with a new strategy able to speed up the biocleaning of complex gypsum crusts.