Xylanase and Cellulase production by a termite associated Xyiaria species
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Date
2006-08
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Addis Ababa University
Abstract
Xyalaria sp. are known to be associated with termites. However, the benefit the
termites get from this association is not yet known. Termites collect wood pieces
from the surrounding and collect it in the mound. The wood is then converted to
soft spongy mass, called comb. The comb is normally invaded with fungal mycelia.
It is well known that termites use cellulose as energy source after degradation to
glucose with the help of microbial cellulases in the gut. But lignified celluloses
can not be digested by cellulases. We hypothesize that the fungus probably helps
to delignify cellulose fiber either directly through lignin degradation or through
removal of the hemicellulose that cement the lignin to the cellulose fiber. To test
this hypothesis we collected termite comb from Zuway and extracted proteins.
The extract showed high xylanase activity (24U/g comb) and no detectable
cellulase activity. This indicates that the role of the fungus is probably to remove
lignin from the cellulose fiber. The fact that there was no detectable cellulase in
the comb indicates that the fungus and the termite are not competing for
cellulose. The fungus was isolated from the comb in pure culture. It was then
grown m culture usmg submerged fermentation (SmF) and solid·state
fermentation (SSF). However, enzyme production in SSF was much higher than
in SmF. Maximum enzyme production in SSF using wheat bran was obtained at a
substrate to moisture level ratio of 1:0.5 to 1:2. Addition of different sugars to the
SSF substrate didn't affect enzyme production, indicating that enzyme production
is probably constitutive. The xylanase was optimally active in the pH range of 4 to
6 and at temperature of 40°c. These properties make Xylaria xylanase potentially
attractive as animal feed supplements.
Key words: Xylaria, Xylanase, Cellulase, Termites
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Keywords
Xylaria, Xylanase, Cellulase, Termites