Agriculture Reference
In-Depth Information
organic matter and decomposers, and results in the formation of a range of end prod-
ucts or compost. The compost has many interesting and useful properties and can
be used as a fertiliser, a substitute for peat in horticulture, a natural pesticide, a soil
conditioner (as it improves soil structure, texture, aeration and water retention), and
a microbial additive to increase enzyme activity as humus (Odlare
2005
). There are
several advantages to the process of composting over incineration of waste material.
Composting is economical, safe, and environmentally favourable. Decomposition
of organic waste by composting instead of incineration avoids the need of oil and
also mitigates the release of CO
2
and other greenhouse gasses into the atmosphere.
Composting is environmentally safe since it does not produce harmful substanc-
es such as nitrogen oxides (NOx), sulfur oxides (SOx), and dioxins. Composting
kills pathogenic microbes and viruses, and also seeds of weeds. Since incineration
is now generally prohibited in many countries, composting has become more im-
portant for decomposing organic wastes than before.
Changes in physico-chemical conditions of compost drive the changes in micro-
bial community structures and composition. Compost has a defined thermophilic
microflora which constitutes the predominant component and provides selectivity
to compost. Thus, the optimisation of compost quality is directly linked to compo-
sition and succession of microbial communities in the composting process. Heat
emitted from fermentation processes of microorganisms causes the inside of com-
post piles to become hot, and thus acts as one of the important environments for
isolating thermophiles (Finstein and Morris
1975
). According to the literature, the
inside temperature reaches up to 75-80 °C (Saiki et al.
1978
). The isolation of many
moderate thermophiles belonging to the genera
Geobacillus, Bacillus
, and
Clos-
tridium
and related species has been reported. Methanogens, including thermophilic
methanogens (which belong to Archaea) have also been isolated from traditional
compost.
6.2
Thermophiles
Of the enormous range of temperatures known (from 0 to approx. 3 × 10
9
K), only
a small fraction is compatible with life. However, significant attention towards ex-
ploring the biodiversity of life at elevated temperatures has established that micro-
bial life can prevail or thrive in the upper as well as lower temperature limits. Life
under extremes of temperature creates a series of challenges, at low temperatures
the structural conformation of the cell is disintegrated due to formation of ice crys-
tals; while at the other extreme the denaturation of biomolecules and cell com-
ponents bring about the destruction of cells at high temperatures. A wide variety
of microorganisms that thrive under these denaturing conditions at elevated tem-
peratures have, however, been discovered and can overcome these challenges. One
such group of microorganisms includes the thermophiles. The word “thermophile”
has been derived from two Greek words “thermotita” (meaning heat) and “philia”
(meaning love). Thermophiles are heat-loving organisms, which not only tolerate
high temperatures but also usually require these for their growth and survival. A
