Biofilm enrichment of spray-paint endemic microbial communities suitable for graffiti bioremoval

Unwanted graffiti made by spray paints are one of the most severe environmental pollutants that affect historical and modern buildings. Microorganisms offer a powerful, safe, eco-friendly, sustainable and low-cost biobased solution to remove graffiti from urban surfaces compared to conventional chemical and physical methods. However, a fully satisfying biocleaning procedure for the removal of spray paint has not yet been achieved due to the complexity of the paint composition, together with the fact that most of microorganisms found on paint films are airborne contaminants rather than active degraders. Spray paints contain xenobiotic compounds, creating an extreme environment for most microbial life. In this research a lab-scale biofilm enrichment strategy was developed to retrieve bacteria suitable for biocleaning purposes from spray paint in cans. Results indicated that this selective strategy i) effectively enriched non-endospore-forming bacteria suited to survive the harsh physicochemical conditions of canned paint; ii) established stable subaerial biofilms on painted surfaces, as demonstrated by metagenomic analysis using Illumina next generation sequencing technology; iii) utilised paint components as the sole carbon and energy source; and iv) remained amenable to large-scale, low-cost production for potential biocleaning applications. The most abundant taxon in both black and silver paints was isolated, sequenced using standard methods and identified as Klebsiella aerogenes.