The Reciprocal Role of Inks, Pigments, and Microbial Metabolism in the Biodeterioration of Historical Parchment Manuscripts

Microbial colonization, especially by proteolytic enzymes that break down the collagen matrix, can cause biodeterioration in historical parchment manuscripts. This study examines the mutual relationship between microbial enzymatic activity and writing materials, particularly historically reconstructed inks and pigments. The biodeteriorated Coptic parchment manuscript CG 8001, which is kept at the Egyptian Museum in Cairo, contained fourteen bacterial strains. Two of these strains (N10 and N13) showed high protease activity and were identified as Serratia liquefaciens N13 (MT279350.1) and Bacillus safensis N10 (PP083218.1) by 16S rRNA sequencing. Using traditional recipes of cinnabar (HgS), orpiment (As₂S₃), verdigris (Cu(CH₃COO)₂), carbon black, and iron gall ink (cold method), all bound with gum arabic, mock parchment samples were made in order to assess how particular writing materials affect microbial degradation. These samples were allowed to air dry before being finely ground and added to culture media that had been inoculated with the two proteolytic isolates. The biodegradability of various coatings was evaluated by tracking enzymatic degradation. The findings demonstrated that orpiment had the most potent antimicrobial activity, considerably preventing enzymatic breakdown. Because they contain copper and mercury, cinnabar and verdigris exhibited a moderate level of resistance. On the other hand, uncoated parchment was extremely vulnerable, and carbon black and iron gall ink offered little to no protection. These results imply that some pigments used in the past had biocidal qualities, which had a direct impact on how differently manuscripts were preserved. This study emphasizes the significance of material selection in conservation planning and the intricate role that writing materials play in microbial biodeterioration. It offers a scientific basis for preventive conservation measures specific to parchment manuscripts by clarifying the ways in which pigment chemistry influences microbial metabolism.