Biodeterioration potential of algae on building materials - Model study

Although biodeterioration of building materials is a well-recognized problem, unlike heterotrophic organisms the influence of aerophytic algae has been so far attributed only to aesthetical and indirect biodeterioration. This article concentrates on determining the influence of mixed algal cultures of Coenochloris signiensis, Stichococcus bacillaris, Klebsormidium flaccidum and Chlorococcum infusionum on brick and plaster samples, studied in model environment. Inoculated and incubated for 28 days samples were examined with chlorophyll a measurements, cell density estimation, microscopic observations, water absorptivity tests, pH determination and metabolome profiling. Algal growth led to the lowering pH values of plaster samples by 0.53–0.54 and brick samples by 0.29–0.36 as well as increasing water absorptivity by 4.65% and 4.76% respectively. CIE L*a*b color measurements revealed material discoloration of ΔE = 16.11 ± 1.38 for brick and ΔE = 16.59 ± 0.73 for plaster samples. Metabolome analysis confirmed high activity of biofilms with 112 metabolites detected on brick and 203 on plaster samples. 25 and 35 metabolic pathways were confirmed respectively. Compounds with documented biodeteriorative potential such as acetic, isobutyric and citric acid were found. The acquired results suggest that the impact of green algae on building substrates goes beyond aesthetic and indirect biodeterioration and should be further explored.