Survival and reproduction of D. hansenii on sapwood
surfaces indicate that it is not necessary to supplement
with nutrients. Addition of nutrients to wood would
carry the risk of stimulating development of disfiguring
fungi by improving the typically low nutrient status
offered by wood, particularly in terms of nitrogen
availability, thus potentially reducing the effect of nutrient
competition between fungi and yeast. Furthermore,
wood surfaces which have become enriched with
water-soluble nutrients, as a result of kiln drying, have
been found to carry an increased susceptibility to molding
(Theander et al., 1993).
The ability of D. hansenii to effectively reduce spoilage
of sterilized wood inoculated with known fungi
indicated an ability to antagonize selected common
wood disfiguring fungi in their natural substrate. The
use of green wood represented an attempt to obtain
information about the ability of the isolate to compete
at wood surfaces against the naturally present microorganisms
in wood, an aspect not tested by the use of
autoclaved wood. The results indicated that the yeast
was also successful in this respect. Reduced disfiguration
of green wood in the presence of the yeast indicated
broad antagonism against many wood disfiguring
fungi. The yeast was also presumably able to compete
for nutrients against this more complex
community of spoilage microorganisms in order to remain
active.
A good biological control agent must not only survive
on the substrate and remain antagonistic to the targets,
but must also remain attached to the substrate.
In this respect, the use of yeasts may be at a disadvantage
because of the risk of them being washed off the
wood. Unlike filamentous fungi, yeasts do not form a
mycelium which anchors them to the substrate and are
therefore at risk of becoming dislodged and washed
away by water. However, Debaryomyces (or Pichia)
isolates were found by Wisniewski et al. (1991) to attach
strongly to the hyphae of mold fungi. This feature
may protect yeast cells in contact with hyphae from
becoming easily washed away. Furthermore, at this
stage the yeast is primarily being investigated as a
potential biological control agent for timber stored in
the sawmill yard, where it is exposed to rain mainly on
the upper surface of stacks. Such potential loss of yeast
through the action of running water is unlikely to be
important in practice because previous observations of
stain development within stacks of sawn timber indicated
that most degrade developed in the center of
stacks where yeasts are unlikely to be exposed to running
water (Payne et al., 1999).
Survival and reproduction of D. hansenii on sapwood
surfaces indicate that it is not necessary to supplement
with nutrients. Addition of nutrients to wood would
carry the risk of stimulating development of disfiguring
fungi by improving the typically low nutrient status
offered by wood, particularly in terms of nitrogen
availability, thus potentially reducing the effect of nutrient
competition between fungi and yeast. Furthermore,
wood surfaces which have become enriched with
water-soluble nutrients, as a result of kiln drying, have
been found to carry an increased susceptibility to molding
(Theander et al., 1993).
The ability of D. hansenii to effectively reduce spoilage
of sterilized wood inoculated with known fungi
indicated an ability to antagonize selected common
wood disfiguring fungi in their natural substrate. The
use of green wood represented an attempt to obtain
information about the ability of the isolate to compete
at wood surfaces against the naturally present microorganisms
in wood, an aspect not tested by the use of
autoclaved wood. The results indicated that the yeast
was also successful in this respect. Reduced disfiguration
of green wood in the presence of the yeast indicated
broad antagonism against many wood disfiguring
fungi. The yeast was also presumably able to compete
for nutrients against this more complex
community of spoilage microorganisms in order to remain
active.
A good biological control agent must not only survive
on the substrate and remain antagonistic to the targets,
but must also remain attached to the substrate.
In this respect, the use of yeasts may be at a disadvantage
because of the risk of them being washed off the
wood. Unlike filamentous fungi, yeasts do not form a
mycelium which anchors them to the substrate and are
therefore at risk of becoming dislodged and washed
away by water. However, Debaryomyces (or Pichia)
isolates were found by Wisniewski et al. (1991) to attach
strongly to the hyphae of mold fungi. This feature
may protect yeast cells in contact with hyphae from
becoming easily washed away. Furthermore, at this
stage the yeast is primarily being investigated as a
potential biological control agent for timber stored in
the sawmill yard, where it is exposed to rain mainly on
the upper surface of stacks. Such potential loss of yeast
through the action of running water is unlikely to be
important in practice because previous observations of
stain development within stacks of sawn timber indicated
that most degrade developed in the center of
stacks where yeasts are unlikely to be exposed to running
water (Payne et al., 1999).
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