Chemical and microbial characterization of cyanobacterial extracellular polymeric substances (EPS) in biofilm extracts from Hathi Khana, An ancient monument in Agra, Taj complex

The Taj Mahal and its complex are iconic symbols of India’s cultural heritage, and preserving their appearance and structural integrity is of utmost importance. The discoloration of ancient heritage structures caused by microbial soiling, particularly the action of cyanobacteria, green algae, and lichens, and the role of Extracellular Polymeric Substances (EPS) secreted by these microorganisms, is an important interdisciplinary study. These microorganisms colonize the surfaces of monuments, leading to aesthetic and structural issues. Various analytical techniques like optical microscopy, FTIR (Fourier-transform infrared spectroscopy), XRD (X-ray diffraction), and Scanning Electron Microscopy (SEM) were used to characterize the biofilm and its components. FTIR analysis revealed interactions between EPS and Nano iron oxide in the biofilm, which contributes to surface discoloration. Airborne particulates minerals such as quartz, feldspar, calcite, and hematite are significant source of surface crust on these monuments. This analytical approach has allowed to unravel the complex features of surface discoloration on these historic structures leading to apply appropriate conservation measures.