Laboratory culturing and decay testing with Physisporinus vitreus and Donkioporia expansa orginating from identical cooling tower environments show major differences
J Van Acker, M Stevens
Both Basidiomycete fungi Physisporinus vitreus (Pers.:Fr.) P. Karst. and Donkioporia expansa (Desm.) Kotl. & Pouz. were isolated from identical cooling tower environments. Azobé heartwood (Lophira alata), a very durable tropical wood species was totally deteriorated in cooling towers in a similar way by both fungi. First attempts to culture Physisporinus vitreus in laboratory circumstances showed a need for climatic conditions with higher temperatures and higher relative humidity compared to standard conditions known for most Basidiomycete fungi. Moreover there is a supplementary need to alter the acidity of the malt-agar medium and to add a protein nitrogen source like pepton. Identical culturing conditions were supposed for the Donkioporia expansa isolate. However the alteration in acidity is not beneficial for the growth of this cooling tower fungus. High mass loss figures up to 50% were recorded for non-durable wood species inducing wood moisture contents of over 150%, but only a slight growth stimulation on azobé could be observed under laboratory conditions.