New biocide for eco-friendly biofilm removal on outdoor stone monuments

Abstract In this study, an eco-friendly biocide was prepared from natural medicinal ingredients that are traditionally used to preserve and maintain outdoor stone monuments in South Korea, and its effectiveness was verified through laboratory testing and on-site application. Eugenol, which was isolated and identified from volatile clove extracts, was mixed together with eco-friendly emulsifiers from the Tween and Span series at different ratios to prepare an optimized biocide. Strong antifungal activities were confirmed when the biocide was tested against 19 types of molds that were isolated and identified from the biofilms of two World Heritage Sites: the Royal Tombs of the Joseon Dynasty in South Korea and the Vat Phou temple in Laos. When applied on-site, the lichen became decolorized and discolored, and was ultimately eliminated from the surface as the mycelium in its epithelial layer disintegrated. Furthermore, an average of 80% reduction in microorganisms was observed from the applied surface based on ATP measurements before and after biocide treatment. The developed biocide shows high prospects for commercial use as part of an eco-friendly technology applicable to outdoor stone monuments.