Some Aspects of the Biodeterioration of Silicone Treated Wood by Soft-Rot Fungi

Abstract

An economic evaluation of wood biodeterioration confirmed the need for improved efficient preservation. An historical survey illustrated a trend of specialisation in timber technology with enhanced selectivity of preservative action and increased accuracy of measuring their performance. A series of model analytical techniques was devised for facilitating the study of cellulolytic microfungal ecology. A novel perfusion device allowed continuous nutrient supplementation of beechwood veneers, a grinding method produced rapid reliable fungal isolation and a tensiometric technique provided precise strength data for monitoring deterioration. Different perfused pH values gave varying responses with fungal communities and monocultures. Some fungi were tolerant, others displayed pH specificity. Behaviour depended on the cellulosic substrate used. Hyphal mixing of bi-cultures followed a pattern capable of formularisation and this reflected cellulolytic activity. Antagonistic, synergistic and neutralistic relationships were recognised. A consistent wood penetration sequence was delineated and found to be a function of hyphal growth rate independent of substrate changes. Moisture affected deterioration but not fungal incidence. Drying did not hasten deterioration. Glucose initially reduced deterioration and species isolated. Asparagine accelerated deterioration but yeast-extract had less effect. Wood extractives allowed decay whilst distilled, rain and soil water gave poor deterioration. Short light wavelengths favoured deterioration, other spectra had less effect. Variable light intensities were uninfluential. Oxygen deficiency prevented deterioration but concentrations above ambient increased deterioration and decreased fungal colonization. Carbon dioxide induced deterioration but did not affect colonization. Substrate oxidation reduced growth and deterioration whereas reduction increased them. Water-repellent silicones were examined for natural preservative qualities. They were screened alone for biodegradeability, toxicity, hydrophobicity and metabolic activity and proved to be inert and stable in all respects to the applied conditions. These investigations initiated the design of a percolator for enrichment culture of potential biodeteriogens. Silicones aided penetration of other toxicants.