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[EN] Microorganisms that can act as biocleaning agents can potentially be isolated from existing graffiti. In this study, a total of 30 different isolates of bacteria, fungi and yeasts were obtained from black, blue, red and silver graffiti coatings exposed outdoors conditions for 10 years. An additional strain was obtained from samples of black powdered graffiti exposed under laboratory conditions for 5 years. Each of the isolates from the most prolific sources (i.e. red and silver graffiti coatings and black powdered graffiti) was evaluated alone and in combination with Tween? 20, to determine their potential as biocleaning agents, in test tube assays. Two strains isolated from the red graffiti coating (identified as Candida parapsilosis) and one strain isolated from the black powered graffiti (identified as Rhodococcus erythropolis) performed best alone. The quantity of live cells throughout the trials and biofilm formation indicated that both strains were able to utilize the paint as a substrate. When the microorganisms isolated were combined with Tween? 20, the quantity of live cells increased notably throughout the incubation time, and turbidity and graffiti discoloration were observed. Infrared spectroscopic examination revealed that R. erythropolis performed the best alone, while the addition of Tween? 20 to C. parapsilosis enhanced the oxidative degradation of the graffiti., J.S. Pozo-Antonio is grateful to the Spanish Ministry of Economy and Competitiveness (MINECO) for a post-doctoral contract (Juan de la Cierva-Incorporacion, IJCI-2017-3277). P. Sanmartin is grateful for financial support from the Xunta de Galicia (grant ED431C 2018/32).

[EN] The first academic studies on the use of microorganisms in cleaning procedures appeared in the late 1980s/early 1990s. In the past thirty years, most of such studies have addressed the removal of nitrate and sulphate salts and organic matter from surfaces by using non-pathogenic anaerobic microorganisms, mainly sulphate-reducing bacteria. The successful use of microbes in the removal of graffiti paint remains, however, a work in progress. Biocleaning surfaces to remove graffiti is not a simple task, because of the complex chemical composition of graffiti paints. This study looks at ways of improving the bioremoval of graffiti and presents the latest findings regarding different methodological aspects of cleaning natural and man-made stone. Granite and concrete substrates were coated with silver and black graffiti spray paints for comparison of the efficacy of the biocleaning method on these different materials. Visual and microscopic examination along with colour and infrared measurements made after application of the bacterial strains tested (previously shown to be suitable candidates for bioremoval of graffiti) revealed remarkably successful results. The findings presented thus represent progress in the development of a biocleaning protocol applicable to the in-situ removal of graffiti. Important improvements have been made regarding the time of treatment, which has been reduced by up to 20 days, and the use of a culture medium enriched with powdered graffiti, which facilitates and accelerates the adaptation of the microorganisms to the target surface., The authors are grateful to Barrie Foundation for the economic support in the purchase of some of the bacterial strains used in the study. The strains were purchased during the period of a scholarship for postgraduate studies abroad (2012 Call) granted to P. Sanmartin.