Antifungal protection of building materials by humic acid derivatives as assessed by ATP-metry

Mycelial fungi are known by their biodestructive activity towards building material samples. In this work the possibility of using various derivatives of natural humic acids as antifungal agents was evaluated using the method of bioluminescent luciferase determination of the adenosine triphosphate intracellular concentration in the mycelial fungi cells. In order to prevent fungal lesions in rooms with high humidity the fungal biocide ACTICIDE® OTP 10 containing 2-octyl-4-isothiazoline-3-one is added to the tile grout; it was used as a comparison sample in our study. Aspergillus niger F-1057 and Stachybotrys chartarum F-993 spores were used as test cultures as the most frequently detected fungal contaminants of building materials. The samples of extracted from coal (leonardite) potassium humate modified with 2-methylhydroquinone, or 1,4-hydroquinone or 2-hydroxy-1,4-hydroxynaphthoquinone were the studied substances. The antifungal activity of potassium humate modified with 2-hydroxy-1,4-hydroxynaphthoquinone to both fungal test objects was confirmed in experiments aimed at studying the condition of intertile joints. The same compound at a concentration of 0.5–5.0 g/L showed noticeable antifungal effect when applied to a universal wallpaper adhesive containing carboxymethylcellulose. Antifungal activity of the same additive was comparable with the action of commercial biocide at the initial stage of the study, and after 32 days of exposure of fungi in contact with the studied additive at a final concentration of 5 g/kg of building material was superior to its action.