Natural antibiofouling agents as new control method for phototrophic biofilms dwelling on monumental stone surfaces

Five natural antibiofoulants with terrestrial (capsaicine - CS, cinnamaldehyde - CI) and marine origin (zosteric acid - ZA, poly-alkylpyridinium salts - pAPS and Ceramium botryocarpum extract - CBE) have been selected and tested against phototrophic biofilm formation on the stone surfaces for their inhibitory properties. The antibiofouling agents (ABAs) were incorporated into two commercial silicone based coatings (Silres BS OH 100 - S and Silres BS 290 - W). In this work, phototrophic growth was evaluated by epifluorescence microscopy and semi-quantitative image analysis. The results showed an inhibitory efficiency for almost all tested ABAs. However, this efficiency has been found for short time or when the incorporating agent were incompletely cured. Among the ABAs tested, the polyalkylpyridinium salts and cinnamaldehyde incorporated into Silres BS 290 showed the best inhibitory efficiency.