6 Wood Discoloration

3.4 Temperature 69
mycelial growth. Cultivation of Lentinula edodes in Asia involves a dipping
of the colonized wood in cold water to stimulate fruit body development. On
the other hand, S. lacrymans is stimulated to fruit in laboratory culture, if
the mycelium is incubated first 3–4 weeks at 25 ◦ C and then 2 weeks at about
20 ◦ C (Fig. 3.1; Schmidt and Moreth-Kebernik 1991b). In some fungi, spore
germination is activated by high temperature, in nature for example after
forest fires.
The temperature curve of the mycelial growth rate must not correlate with
that one of fungal activity. For example, the temperature range for growth
may be broader than for wood degradation (Wälchli 1977). Furthermore, the
temperature optima of enzymes isolated from fungi are often higher (50–
60 ◦ C) than those of mycelial growth of the respective fungus. Some wood
fungi tolerate extreme values beyond minimum and maximum by resistance
to cold and heat, respectively. However, there are significant differences with
regard to the test method used. Results from cultures on agar revealed that
S. lacrymans survived 1 h at 55 ◦ C, Coniophora puteana 1hat60 ◦ C, Antrodia
vaillantii 3hat65 ◦ C (Schmidt 1995a), and Gloeophyllum trabeum 1hat80 ◦ C
(Mirič and Willeitner 1984). In colonized wood samples that were slowly dried
before heating, S. lacrymans survived 4 h at 65 ◦ C, C. puteana 4h at 70 ◦ C, A.
vaillantii 4h at 80 ◦ C and G. trabeum 4h at 95 ◦ C, assumably by developing
resistant arthrospores (Huckfeldt et al. 2005). This great resistance of the fungi
to heat challenges the use of a heat treatment procedure for the eradication
of fungi in houses. In Denmark, whole houses are subjected to heat treatment
against S. lacrymans (Koch 1991) (Chap. 8.5.4).
Vegetative cells (bacteria and fungal hyphae) are destroyed by heating at
80 ◦ C (pasteurization). Exceptions with growth of up to 113 ◦ Carebacteria
(Archaea) in volcanic biotopes (geysers, black smokers). Spores are frequently
Fig.3.1. Fruit body formation of Serpula
lacrymans in laboratory culture stimulatedbyawarmthtreatment;25mycelial
growth at 25 ◦ C, 20 growth increase at
20 ◦ C, F fruit body
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