Waterlogged archaeological wood—chemical changes by conservation and degradation

AbstractErosion bacteria are the main degraders of archaeological wood excavated from waterlogged environments. Light microscopy and analytical pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC/MS) were exploited to study waterlogged archaeological wood (Pinus sylvestris L.) at different stages of bacterial decay. The research explored the biochemical changes related to erosion bacteria degradation of the secondary cell wall in the wood cells and the chemical changes related to abiotic processes induced by the long-term waterlogged burial environment. Erosion bacteria were demonstrated by chemical analysis to cause significant holocellulose depletion. Detailed analysis of the holocellulose and lignin pyrolysis products revealed only minor chemical changes in the residual structure even after heavy erosion bacteria decay. Chemical changes in the lignin polymer is associated to enzymatic unlocking of the lignocellulose to gain access to the holocellulose fraction of the cell wall. Chemical changes in the holocellulose fraction are suggested to stem from depolymerisation and from alterations in the polymer matrix of the residual wood cell wall structure. Interestingly, a difference was observed between the sound reference wood and the waterlogged archaeological wood without erosion bacteria decay, indicating that long-term exposure in waterlogged environments results in partial decay of the holocellulose even in absence of bacterial activity.

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Even Visually Intact Cell Walls in Waterlogged Archaeological Wood Are Chemically Deteriorated and Mechanically Fragile: A Case of a 170 Year-Old Shipwreck

Molecules ◽

10.3390/molecules25051113 ◽

2020 ◽

Vol 25 (5) ◽

pp. 1113 ◽

Cited By ~ 1

Author(s):

Liuyang Han ◽

Xingling Tian ◽

Tobias Keplinger ◽

Haibin Zhou ◽

Ren Li ◽

...

Keyword(s):

Cell Wall ◽

Cell Walls ◽

Intact Cell ◽

Nitrogen Adsorption ◽

Wet Chemistry ◽

Archaeological Wood ◽

Waterlogged Archaeological Wood ◽

X Ray Scattering ◽

Crystallite Structure ◽

Cell Wall Mechanics

Structural and chemical deterioration and its impact on cell wall mechanics were investigated for visually intact cell walls (VICWs) in waterlogged archaeological wood (WAW). Cell wall mechanical properties were examined by nanoindentation without prior embedding. WAW showed more than 25% decrease of both hardness and elastic modulus. Changes of cell wall composition, cellulose crystallite structure and porosity were investigated by ATR-FTIR imaging, Raman imaging, wet chemistry, 13C-solid state NMR, pyrolysis-GC/MS, wide angle X-ray scattering, and N2 nitrogen adsorption. VICWs in WAW possessed a cleavage of carboxyl in side chains of xylan, a serious loss of polysaccharides, and a partial breakage of β-O-4 interlinks in lignin. This was accompanied by a higher amount of mesopores in cell walls. Even VICWs in WAW were severely deteriorated at the nanoscale with impact on mechanics, which has strong implications for the conservation of archaeological shipwrecks.

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New trials in the consolidation of waterlogged archaeological wood with different acetone-carried products

Journal of Archaeological Science ◽

10.1016/j.jas.2011.06.012 ◽

2011 ◽

Vol 38 (11) ◽

pp. 2957-2967 ◽

Cited By ~ 28

Author(s):

Gianna Giachi ◽

Chiara Capretti ◽

Ines D. Donato ◽

Nicola Macchioni ◽

Benedetto Pizzo

Keyword(s):

Archaeological Wood ◽

Waterlogged Archaeological Wood

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Identification of Bacteria from Waterlogged Archaeological Wood

Heritage Microbiology and Science ◽

10.1039/9781847558633-00151 ◽

2008 ◽

pp. 151-155

Keyword(s):

Archaeological Wood ◽

Waterlogged Archaeological Wood ◽

Identification Of Bacteria

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Essential Oils as Alternative Biocides for the Preservation of Waterlogged Archaeological Wood

Microorganisms ◽

10.3390/microorganisms8122015 ◽

2020 ◽

Vol 8 (12) ◽

pp. 2015

Author(s):

Federica Antonelli ◽

Marco Bartolini ◽

Marie-Laure Plissonnier ◽

Alfonso Esposito ◽

Giulia Galotta ◽

...

Keyword(s):

Essential Oils ◽

Inhibitory Concentration ◽

Treated Wood ◽

Biological Degradation ◽

Archaeological Wood ◽

Waterlogged Archaeological Wood ◽

Materials Used ◽

And Storage ◽

Generation Sequencing

Waterlogged archaeological wood is exposed to a high risk of biological degradation during the post-excavation phases of storage and restoration. For this reason, often biocides must be used to preserve wooden remains. In the present work three essential oils (cinnamon, wild thyme, and common thyme) were tested as possible alternative biocides to use in the preservation of waterlogged archaeological wood. The oils were first tested in vitro to establish the minimum inhibitory concentration (MIC) and to evaluate the biocidal activity on selected fungal strains. Then, the established MIC was applied on waterlogged archaeological wood samples and during an actual restoration treatment. The effectiveness of the oils was evaluated through cultural analyses, ATP quantification, and next-generation sequencing. The results showed that the oils caused a significant decrease in the vitality of fungal mycelia grown in vitro and of the microbiota present in treated wood and storage water. Furthermore, an influence on the composition of the bacterial communities of treated wood samples was observed. Although further tests are needed to evaluate interferences with the materials used during restoration procedures, essential oils could be considered as a possible alternative to the currently used biocide.

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