Biochemical and chemical markers associated with biodeterioration agents isolated from archive audio-visual materials

Biodeterioration of cultural heritage objects, including audio-visual materials, is driven by complex microbial metabolic processes that remain incompletely understood. This research addresses this gap through a model study using bacterial (Bacillus spp.) and fungal (Alternaria, Aspergillus, and Penicillium spp.) isolates on archival photographs with different binders—albumen, collodion, and gelatine. We examined the enzymatic activities, metabolomic profiles, and structural impacts of microbial colonisation over a two-month period. Isolates demonstrated specific degradation capabilities, with proteolytic and cellulolytic activities prominently observed. Metabolomic analysis revealed a significant production of carboxylic acids and organooxygen compounds across all isolates and binders, indicating common biodegradation pathways involving the breakdown of complex molecules such as cellulose. Gelatine emerged as the most conducive substrate for microbial growth and metabolic activity, exhibiting distinct metabolic profiles compared to collodion and albumen. SEM analysis uncovered preferential colonisation patterns, notably the preference of the Alternaria genus for collodion. The microbial activity resulted in measurable changes in pH, colour, and mechanical properties of the materials, with albumen elongation drastically reduced to 0.76%. Our findings elucidate the microbial metabolic processes driving the biodeterioration of photographic materials, providing crucial insights for developing targeted preservation strategies to safeguard audio-visual cultural heritage.