Deterioration of ancient Korean paper (Hanji), treated with beeswax: A mechanistic study

•Oxidative group profiling of small ancient cellulose fragments coated with beeswax.•The main mechanism of deterioration was identified for the first time.•Beeswax coated cellulose was purely hydrolytically damage, no oxidation.•Hydrolysis caused by microorganisms secreting cellulolytic enzymes. In the early 15th century, beeswax coating was applied to some of the cellulosic documents in a futile attempt to better conserve the paper. However, this treatment caused much more severe degradation compared to untreated Hanji. In the current study, the degradation pathway of this beeswax-treated Hanji has been clarified for the first time. The degradation of cellulose was investigated by labeling of oxidized groups combined with gel permeation chromatography, providing profiles of carbonyl and carboxyl groups relative to the molar mass distribution. The beeswax caused purely hydrolytic damage, leading to a decrease in molar mass to about one fifth of the original value. Oxidative degradation, by contrast, did not occur to any significant extent. Hydrolysis was not caused by acids but by microorganism feeding on the beeswax and excreting cellulolytic enzymes, which cause similar cellulose damage patterns. The hydrolytic enzymes were identified by typical metabolites present in the Hanji.