Biomedical Engineering Reference
In-Depth Information
The termite population and the number of individuals are huge (some groups
have hundreds of millions of termites) with a wide variety (now known worldwide
as having more than 2,000 types) and a wide distribution (distributed outside in
most areas except for extremely cold areas and higher elevations of the mountains).
Cellulase activities differ from different populations of termites. In nature, termites,
especially ground-living termites, decompose the cellulose of dead plants rapidly
with a tremendous number of individuals and plays an irreplaceable role in the cycle
of substances on Earth [
21
].
Termites, with lignocellulose as a diet, play an important role in the mass cycle
of nature. There is a wide range of food, including timber (intact or decomposed),
plant leaves, humus, paper debris, herbivore feces, and so on. Live nutrients of
termites mainly depend on the participation of endogenous and exogenous cellulase
degrading lignocellulose into nutrients that can be completely absorbed and utilized.
A study showed that the major digestive enzymes for cellulose in the digestive
system of termites were endo-(1-4)-
“
-glucanase and
“
-glucosaminidase, which have
high activities.
-Glucosaminidase can quickly decompose cellobiose and other low
molecular oligosaccharides into glucose and enhance the absorption of the termite,
which will benefit decomposition and utilization of cellulose.
The reason for termites to take cellulose as food is that its body contains many
kinds of microorganisms and bacteria. There is a symbiotic relationship between
microorganisms and termites. Only with the assistance of these microbes can
termites digest cellulose completely [
22
].
“
3.2.2.2
Earthworms
Among all invertebrates in temperate soil, the earthworm has the largest biomass.
In recent years, the straw used for no tillage and minimum tillage of soil provided
favorable conditions for the activities and reproduction of earthworms. The earth-
worms swallow much soil and surface fallen residues. Through feeding, mining, and
excretory activities, organic debris and mineral soil are mixed, and the degradation
of organic matter is accelerated. Thus, the transformation of soil organic matter
and nutrient cycling in earthworms plays an important role. Earthworms are also
widely used for the treatment of organic waste. The Lausanne Experiment Station
of England, using earthworms to treat agricultural waste, garbage, and sludge,
has achieved industrialization and commercialization of earthworms. In addition,
earthworms abound in protein and are fed as protein additives. Earthworms feed
on lignocellulose and can take glucose generated from cellulose hydrolysis as the
energy substances of growth and development.
Because its gastrointestinal system is different from that of herbivores, the
hydrolysis of the cellulose enzymes of earthworms may be different from that
of rumen microorganisms and even perhaps animal enzymes. It is necessary to
