SOME OBSERVATIONS ON THE USE OF ENZYMES IN PAPER CONSERVATION
Pia C. DeSantis
7 SUMMARY AND CONCLUSIONS
- It is not absolutely necessary to meticulously maintain an enzyme's prescribed temperature and pH optima. The enzyme can function as an efficient catalyst even if only one of these conditions is met.95
- Before purchasing an enzyme, the conservator should consult Boyer's The Enzymes. These volumes not only provide reliable methods for the inactivation and denaturation of each enzyme, but also include the particular characteristics that would favor the use of one enzyme over another.
- Although the product literature implies that enzymes cannot withstand storage at room temperature, the author found that enzymes remaining in a paper exposed for five weeks to dust, light and room temperature could be reactivated. Clearly, effective rinsing is an important part of a treatment procedure, and after rinsing an inactivation step should be considered.
- Inactivation of an enzyme by alcohol as well as denaturation of an enzyme by heat can be reversed if the enzyme is returned to a moist environment having a pH and temperature within its stability ranges. The complete reactivation, however, of any inactivated or denaturated enzyme that might remain in a treated artifact is unlikely. Nonetheless, one should take precautions to keep the possibility of reactivation to a minimum. Such precautions include using a minimal amount of enzyme and rinsing the object thoroughly before considering a solvent inactivation step.
- The results of the tests run on specimens treated with the A.saitoi protease are encouraging. Enzyme treated specimens of newsprint and Rives fell below the controls in only a few cases, and even then by small amounts. Moreover, when compared with the differences between pre-aged and post-aged controls, the differences between pre-aged and post-aged enzyme treated specimens do not appear significant.
- The A.saitoi protease, which was used in all the tests presented in this article, is a good candidate for use in conservation. The A.saitoi protease is not stabilized by calcium, does not require buffers to work in conditions of pH 6 or lower, and is completely and irreversibly inactivated by solutions brought to pH 8 with any divalent cation the conservator might choose. The minimum time and pH required to achieve irreversible inactivation has yet to be determined, but inactivation can be obtained by a ten minute soak in ethanol as well as by a ten minute soak in deionized water raised to pH 7.8 with calcium or magnesium.96
I would like to thank Mrs. Antoinette King and the faculty and students of the Conservation Center, Institute of Fine Arts, for their advice and support in the early stages of this study, and Catherine Nicholson, Shelley Fletcher and Nancy Ash of the Paper Lab, National Gallery of Art for their invaluable instruction and ideas for the testing section and final drafts of this paper. I would also like to thank Randall L. Holton for his assistance in editing.