Biology Reference
In-Depth Information
microorganisms is made of bacteria, fungi, algae, protozoa, and viruses
(microorrganisms are important in industrial and aquaculture.html).
Bacteria can play an important role in mass transfer and utilisation of
substrate in bioremediation of aquaculture (Van Loosdrecht et al., 1987a,
b). Microorganisms reside in the sediment and other substrates, and in the
water of aquaculture facilities, as well as in and on the cultured species
BIOREMEDIATION
Bioremediation is a general concept that includes all those processes
and actions that take place in order to biotransform an environment,
already altered by contaminants, to its original status (Thassitou and
Arvanitoyannis, 2001). Microorganisms can be isolated from almost any
environmental conditions. Microbes will adapt and grow at sub-zero
temperatures, as well as extreme heat, desert conditions, in water, with
an excess of oxygen, and in anaerobic conditions, with the presence of
hazardous compounds or on any waste stream. The main requirements
are an energy source and a carbon source. Because of the adaptability of
microbes and other biological systems, these can be used to degrade or
remediate environmental hazards (Vidali, 2001). The currently recognised
probiotics that may infl uence fi sh immunity, disease resistance and other
performance indices include:
Bacillus subtillis, Bacillus licheniformis, Bacillus
circulans, Lactobacillus rhamnosus, Lactobacillus delbrueckii, Carnobacterium
maltaromaticum, Carnobacterium divergens, Carnobacterium inhibens,
Enterococcus faecium, Saccharomyces cerevisiae
and
Candida sake
(Gatlin et
al., 2006). As the aquaculture industry develops, effective, cost-effective
and environmentally friendly preventive and bioremediation methods of
improving effl uent water quality prior to discharge into receiving waters
of sensitive areas will be necessary (Jones et al., 2001).
Bioremediation, although considered a boon in the midst of present day
environmental situations, can also be considered problematic because,
while additives are added to enhance the functioning of one particular
bacterium, fungi or any other microorganisms, it may be disruptive to
other organisms inhabiting that same environment when done
in situ
(Sasikumar and Papinazath, 2003). A successful bioremediation involves:
optimising nitrifi cation rates to keep low ammonia concentration;
optimising denitrifi cation rates to eliminate excess nitrogen from ponds
as nitrogen gas; maximising sulphide oxidation to reduce accumulation of
hydrogen sulphide; maximising carbon mineralisation to carbon dioxide
to minimise sludge accumulation; maximising primary productivity that
stimulates shrimp production and also secondary crops; and maintaining
