Natural compounds as additives in paints for controlling algae growth

Abstract

Algae are a diverse group of photosynthetic organisms ranging from microscopic single-cell micro-organisms to very large organisms such as seaweed. Microalgae belonging to Chlorophyta (green algae) and Cianophyta (blue-green algae) commonly occur in biofilms. Actually, these phototrophic biofilms are complex microbial communities formed by cyanobacteria, microalgae and heterotrophs (1) all embedded in a mucilaginous matrix of exopolymeric substances (EPS), mainly composed of polysaccharides ranging between 50% and 90% (2). Phototrophic biofilms can produce aesthetic effect and deterioration of building painted surfaces (3). It is a common practice to treat these surfaces with mechanical brushes and/or biocides in order to eradicate the microorganisms present. Several chemicals have been used for this purpose, such as acids, pyridines (4), quaternary ammonium salts (5) and organometallic compounds (6). However, some of these products have been banned over time due to their associated environmental and health hazards (7). An alternative to those compounds, it is the use of ecofriendly natural substances with known biocidal properties. The approach of using natural substances and herbs has been gaining prominence in the field of cultural heritage and conservation sciences since the 2000s (8). Here we present the evaluation of the algaecide properties of isoeugenol, vanillic acid and carvacrol incorporated in an acrylic waterborne paint formulation.