The influence of microfilamentous fungi on wooden organ pipes: One year investigation

Wooden pipe organs are precious objects of cultural heritage the degradation of which has been very poorly studied. Fungal strains recovered from an organ dating back to the 19th century included Alternaria mali, Eurotium cristatum, Aspergillus amstelodami, Penicillium crustosum and Aspergillus sydowii. These isolates were used to artificially contaminate wooden pipes treated with linseed oil varnish and varnish-free. The pipes were incubated at different temperatures and relative humidity for one year. The pipes, incubated at a high relative humidity (70-75%), collapsed due to the biodegradation of glued joints. After one year, inoculated strains (Alternaria mali, Penicillium crustosum and Aspergillus sydowii) as well as some non-inoculated Talaromyces rugulosus, Paecilomyces formosus, Cladosporium cladosporioides, Aspergillus versicolor and Epicoccum nigrum were recovered from the pipes. Few strains exhibited lignolytic activity, while almost all were able to hydrolyze the rabbit glue used to join the wood elements of the pipes. A newly developed portable pipe-sound controller did not detect differences of sound spectra between the uncontaminated and the few surviving contaminated pipes. In this study we have demonstrated that glue degradation was critical for pipe preservation and it can be tremendously accelerated above a certain relative humidity threshold. Therefore, it is important to apply a monitoring strategy able to check the environmental conditions, microbial contamination and pipe sound alteration in order to preserve these valuable and rare cultural heritage objects.