Encyclopedia of biodiversity encyclopedia of biodiversity, (7 volume set) ( PDFDrive ) 2222

Fungi

camembertii. Fungi are also essential for chocolate: the naturally bitter cocoa beans are processed into a sweet tasty candy
by a "fermentation" (sensu food-scientists) using Candida
krusei and Geotrichum.

Biopulping and Bioremediation
Several important industrial process, which have the potential
to be great boons to ecosystem health, are in the pilot stage:
biopulping and bioremediation. The lignin-degrading enzyme
system of Phanerochaete chrysosporium is special for these two
uses. One of the biggest energy and pollution expenditures in
paper making comes from removal of the brown lignin from
wood so that the white cellulose is all that is left to make
paper. What if paper companies could use the enzymes of a
fungus to remove the lignin? This could result in a savings in
both energy and time and avoid the polluting wastes that are
commonly dumped out of the mills. This process is known as
biopulping. There are several products in the pilot stage, but
no large-scale biopulping is yet being done.
To understand this system, you must know that wood
consists primarily of cellulose, which is white, and lignin,
which is brown. Members of Phanerochaete and other genera
cause a white rot of wood. That is, the fungus decays the lignin
and leaves the cellulose behind. There are also fungi that cause
a brown rot, digesting the cellulose and leaving the lignin
behind. Many kinds of fungi cause a white rot, but P. chrysosporium has several features that might make it very useful.
First of all, unlike some white rotters, it leaves the cellulose of
the wood virtually untouched. Second, it has a high optimum
temperature (about 40 1C), which means it can grow on wood
chips in compost piles, which attain a high temperature. These

characteristics point to some possible roles for this fungus in
biotechnology applications. The basis for all of Phanerocaete’s
powers come from its enzymes that can degrade lignin. This
same enzyme system can also degrade chemicals that are
chemically similar to lignin.
Some of the lignin-degrading enzymes of P. chrysosporium
will also degrade toxic wastes, such as PCBs (polychlorinated
biphenyls), PCPs (phencyclidines), TNT (trinitrotoluene), and
similar chemicals. The structure of these chemicals is similar to
that of lignin, and the ligninase enzymes will work on them.
The fungus performs well on the laboratory bench, but as with
many industrial bioprocesses, there are difficulties in scaling
up the process. Nonetheless, this procedure has the potential
to clean up some industrial and toxic waste sites.
In my lab, Adam Gusse, Paul Miller and Volk (2006)
published a paper on the biodegradation of phenolic resin
plastics with Phanerochaete chrysosporium. We demonstrated the
ability of this white-rot fungus to degrade phenolic resin, a
previously nonbiodegradable industrial polymer (plastic-like)
that is not commercially recycled. These phenolic resin polymers, first known as Bakelite, are found gluing layers of plywood together, providing the binding matrix to particleboard,
or laminating the surface of FormicaTM counter tops. They are
also used in constructing rotary telephone casings, bowling
balls, toilet seats, motor casings, and many other everyday
products. The annual production of phenolic resin is 2.2
million tons per year. Formerly considered to be nonbiodegradable and contributing greatly to landfills, our work

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has demonstrated, through three lines of independent evidence, that phenolic resin polymers can be degraded by Phanerochaete chrysosporium. (See TomVolkFungi.net for further
information.)

Threatened or Endangered Fungi
Like the proverbial canary in the coal mine, fungi may be the
first indicators of things going wrong in ecosystems. Remember that fungi are the threads that tie the whole food web
together, since they are the primary decomposers and aid most
plants as mycorrhizae in the absorption of minerals and water.
Thus if something goes wrong with the fungi – if they disappear – there may be dire consequences for any plants and
animals that are dependent on them. Lichens have already
been proven to be accurate indicators of air quality, in both
their quantity and diversity.
Several European countries maintain ‘‘red lists’’ of threatened or endangered fungi. One fungus that may be a candidate for the endangered species list in the United States
is Bridgeoporus nobilissimus, a polypore fungus with a very
large, perennial fruiting body (Figure 20). For a long time
this fungus was in the Guinness Book of World Records as
the largest known fruiting body of a fungus, at over 160 kg
(300 pounds)! There are just eight known sites in Oregon,
Washington, and California at which B. nobilissimus is now
known to occur. It is considered by many to be a rare and
probably endangered fungus. The main reason for this designation is that it is restricted to very large specimens of noble fir
(Abies procera) and occasionally Pacific silver fir (Abies amabilis)
with a diameter at breast height (dbh) of 1–2 m. Trees of this
diameter are not very common. This fungus is considered
endangered because its habitat is endangered. Unfortunately,
it is not clear whether the U.S. Endangered Species Act applies
to fungi. In this zoocentric world, most people are more
interested in the ‘‘charismatic megafauna’’ than in some
‘‘lowly’’ fungus. However, the fungi have many important roles
to play in the ecosystem and should not be ignored. No
ecosystem could exist for long without fungi!

Figure 20 The author with Bridgeoporus nobilissimus on a large
host tree of Abies procera (noble fir).