The Biodeterioration of Paper: a Summary of the Most Common Problems and Diagnostic Approaches

Books, documents, and art items supported on paper are objects easily attacked and degraded by microorganisms. They are mostly made of organic compounds such as cellulose, an ideal substrate for developing many species of fungi and bacteria. Across the centuries, the probability that an object made of paper is colonised and degraded by some saprophytic microorganism is consistent. The challenge for conservators and those involved in preventing the deterioration of cultural heritage is to slow down these inevitable natural processes as much as possible (Pinzari et Sequeira, 2022). Moreover, the functional and biological diversity of species of microorganisms capable of degrading cellulose is exceptionally high because many species have evolved in the most diverse environments to compete for such a widespread carbon source. Thus, the forms of cellulose degradation, whether in natural settings such as soil or anthropogenic environments such as libraries, can differ significantly depending on the species of microorganisms involved and the microenvironment in which they thrive. Although the processes of paper biodeterioration have been the same since the paper was invented, the investigation techniques have significantly changed. After decades of intensive study, there is a clear sense of the enormous complexity of the mechanisms involved and how difficult it is to standardise diagnosis and intervention methods. This is especially true when biodeterioration affects valuable, unique, artistic objects.