Biocleaning of starch glues from textiles by means of α-amylase-based treatments

Abstract

Glues based on starch are widely used for the consolidation of brittle fibres in historic and archaeological textiles. Aging fabrics are affected by hydrolysis/oxidation and cross-linking of these glues, a decrease of glues' solubility, the formation of cracks, and discoloration. The hydrolytic action of enzymes on starch-based glues is promising, as molecular recognition offers great selectivity. However, a systematic assessment of the best methods for applying enzymatic formulations has not been explored yet. Here, α-amylase was applied either by pipetting a solution or combining with gellan gel (embedded in the gel or spread on the gel surface). The effectiveness of the different formulations on the removal of potato and wheat starch was evaluated by Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM) and colorimetric measurements. Enzymes dispersed in gel showed weak diffusion at the surface, resulting in poor starch breakdown and removal. On the contrary, amylase applied by pipette and spread on gel resulted in high starch removal selectivity and efficiency, with neither swelling nor damage to the fibres. These results validate protocols for the assessment of the enzymatic activity on glue-consolidated fibres, identify best application methods and confirm the excellent properties of amylase dispersions for the conservation of historic and archaeological textiles. Key points1. Application of α-amylase by pipette and combined with gellan gel to remove starch glues from wool. 2. Systematic assessment of the best application methods following a multi-analytical protocol. 3. Enzymes dispersed in gel exhibit poor diffusion at the surface, leading to weak starch removal. 4. Enzymes applied by pipette and spread on gel are efficient in starch cleaning, without damage to the fibres.

Wheat-Based Glues in Conservation and Cultural Heritage: (Dis)solving the Proteome of Flour and Starch Pastes and Their Adhering Properties

“…However, the flour-based glue can deteriorate for two main reasons: its own inherent aging process and its potential to serve as a food source for microorganisms. Both factors can damage objects, making removing the glue often necessary, usually through enzymatic methods. ,− For these reasons, starch-based glues can indeed have the advantage of being less likely to interfere with analytical studies. Protein-based glue, such as flour glue, could introduce analytical ambiguities when identifying biological materials in an artifact, as the proteins from the glue may confound the identification of intrinsic biological material.…”