Enzymes as tools for conservation of works of art

Since the early 1970 s, enzymes have grown more and more popular among conservators, initially in pa- per and gradually also in other specialties. Hydrolytic enzymes, or hydrolases, have been most commonly used, for their ability to catalyze hydrolysis of proteinaceous-, polysaccharide- and lipid-based materials that often alter the appearance and the structure of works of art. This action enables the removal of the disturbing materials under milder experimental conditions than would normally be required with more traditional approaches, like organic solvents or alkaline media. Throughout four decades, our knowledge on the mode of action and on the parameters that regulate enzyme activity has steadily made significant progress. Meanwhile, the availability of pure enzymes has also enormously increased. Enzymes can thus be considered useful materials and predictable methods for operators in many disciplines of conservation. This paper reviews the development of the use of enzymes in conservation and presents the state of the art of the current knowledge.