Unveiling the presence of microbial biodeteriogens in paper artifacts through HyperSpectral imaging

Abstract

Microbial biodeterioration constitutes a pervasive deterioration mechanism in cellulose-based heritage materials, where enzymatic depolymerization and metabolite-induced chromatic alterations compromise both the structural integrity and the legibility of the artifact. The development of rapid, non-invasive diagnostic methods with high spatial resolution is particularly urgent, as conventional microbiological and molecular assays are time-consuming, destructive, and often inadequate for capturing the heterogeneity of microbial contamination. In this context, the present work evaluates the diagnostic potential of HyperSpectral Imaging (HSI) in the VNIR (400–1000 nm; 25,000–10,000 cm -1 ) and SWIR (1000–2500 nm; 10,000–4000 cm -1 ) ranges, integrated with chemometric processing for the detection, classification, and distribution of microbial colonization. Microorganisms from 20th-century case studies were isolated, cultured, and inoculated onto Whatman paper fragments, selected as a chemically homogeneous cellulose substrate to separate microbial spectral signatures from the confounding effects of paper additives. The acquired spectral data were analyzed with the Spectral Angle Mapper (SAM) algorithm to detect microbial growth patterns and assess the spatial extent of colonization (size of the biodegraded area). SAM analysis identified the 5400–4500 cm -1 interval as the most discriminative, producing high-contrast maps that clearly distinguish microbial colonies from uncontaminated paper. The absorption feature at 4893cm -1 , likely linked to proteinaceous microbial secretions, enhanced the morphological definition of the colonized areas. Additional SWIR sub-ranges confirmed localized microbial patterns corresponding to actual colony distribution.