Prof. em. Dr. Franc Pohleven, mycology

It was mushrooms that grew round his childhood home that prompted Franc Pohleven to study biology.

He graduated in fungal physiology in 1988 under Prof. Nada Gogala, PhD. His first work as a teacher focused on the physiology of mycorrhizal fungi, which was unchartered territory at the time when the focus was on the investigation of the appearance of their fruiting bodies, or sporocarps. After 1990 he worked as a researcher and professor at the Department of Wood Science and Technology, the Chair of Wood Pests, Modification and Protection of Wood. He specialized in saprophytic fungi, i.e. wood decomposers, in particular the biochemical processes in the mycelium, and their living conditions. This knowledge is useful both in the effective prevention of wood rot and in the cultivation of mushrooms for nutritional and medicinal purposes.

He has applied his research in the field of wood protection, in particular for listed cultural heritage. In terms of pest control he has worked to develop methods used to create conditions that are unfavourable for fungal growth, and biocides that are more targeted and less harmful for the environment, so as to eliminate the use of chemicals in the protection of wood. He achieved this by developing and patenting the procedure for the thermal modification of wood in a vacuum. He was also the first to distinguish between the hazardous procedure of fumigation with toxic gases and less harmful asphyxiation with argon, CO₂, or nitrogen, and thus made an important contribution to the conservation practice.

Up until his retirement he taught and introduced new courses in biotechnology on higher fungi, mushroom cultivation, mycoremediation (a cleanup method that uses fungi to detoxify the environment) and conservation in various fields of study (wood science and technology, agronomy, art restoration, biotechnology). He continues to lecture on mushroom cultivation at the Faculty of Agriculture and Life Sciences of the University of Maribor. Aware that fungi still haven’t been sufficiently harnessed to serve science and people he still researches the physiology of fungi and their medicinal properties: “… and I want them to receive the attention they deserve. The application of fungi is possible when we know their physiology. When you have studied the processes, you can apply them in pharmacy, biotechnology, environmental remediation, and detoxification of protected objects. This is where we have really made a mark.”

The bulk of the work takes place in laboratories equipped with sterile work equipment, such as autoclaves and laminar flow hoods, microscopes, and tools for tracking mycelium growth and wood decomposition processes, growth chambers, refrigerators for the storage of fungal cultures (fungal bank) as well as a wood impregnation chamber and a thermal modification chamber. The laboratories and the equipment are situated at the Department of Wood Science and Technology of the Biotechnical Faculty of the University of Ljubljana. Here, a group of scientists and students tests synthesised compounds and their impact on fungi and wood, or in other words their fungicidal properties. They also test and define the conditions for mushroom cultivation and conduct various experiments to generate ideas for state-of-the art natural wood preservatives and the application of fungi in biotechnology.

Occasionally they work in the field as well, most often when they have a concrete, defined research task and the testing does not require sterile conditions. Franc Pohleven has worked with many scientists of various profiles – wood technologists, biologists, biotechnologists, agronomists, chemists, conservators, architects, civil engineers, and others.

In his doctoral dissertation he established the effect of growth hormones (cytokinins, auxins) in the regulation of mycorrhiza between the fungal mycelium and lateral roots of higher plants. The research he conducted within the Department of Wood Science and Technology delivered several patents, two of which resulted in industrial production, namely the Silvanolin wood preservative and the process of thermal modification in a vacuum. The Silvanolin wood preservative contains biocides that are less harmful for the environment and people, but are effective against wood pests, fungi, and leaching. Thermal modification at temperatures between 170 and 240 °C improves the dimensional stability of wood and its resistance against pests as well as its resonant qualities.

Franc Pohleven was the first to differentiate between fumigation and asphyxiation in the conservation and protection of cultural and historical objects. Fumigation uses toxic gases and can be performed only by qualified professionals (toxicologists) under very strict conditions. Asphyxiation, on the other hand, requires nitrogen, carbon dioxide, or inert gases that are not toxic but nevertheless lead to the suffocation of wood decay fungi at sufficiently high concentrations.

Franc Pohleven studied the asphyxiation of wood decay fungi using argon gas in collaboration with the Metropolitan Museum of Art in New York. Argon is a noble gas and unlike nitrogen or carbon dioxide is highly inert, which is of utmost importance in the conservation practice, for it does not affect wood properties and the appearance of a painted surface (e.g. in altars, sculptures, artworks), and suffocates the pest faster and more effectively.

Written by Tajda Jerkič