Microbial Remediation of Fish and Shrimp Culture Systems and their Processing Industry Wastes - Aquaculture Microbiology and Biotechnology - page 205

Submerged Fermentation
In contrast to solid state fermentation, submerged fermentation is the
process in which the growth and mass multiplication of microorganisms
is carried out in well-defi ned liquid medium enriched with carbohydrate,
nitrogen and other essential nutrients in sterilized bioreactor designed
to maintain optimum pH, temperature, aeration, etc. for quality bio-
inoculants production and the product (bio-inoculants) is totally free from
outside contamination in such system (Ray et al., 2008).
COMMERCIAL PRODUCTS
Microbial remediators commercially available in the market mainly include
organic detritus decomposers, nitrifi ers, sulphur bacteria; Bacillus spp.
and Pseudomonas spp. ( Table 8.2 ) as well as probiotics (lactic acid bacteria).
The bacteria used in these formulations are selected specifi cally for their
ability to degrade organic materials, nitrifying ammonia and/or oxidizing
hydrogen sulphide. In brief, they perform the following functions:
￿ Improve water in aquaculture systems
￿ Reduce ammonia levels, nitrates, algae and sludge buildup
￿ Reduce risk of infection and improves survival rates
￿ Reduce stock losses due to toxic ammonia
￿ Reduce or eliminates time required to oxidize the bottom of ponds
between growing cycle.
Probiotics are mostly used to control various bacterial and viral
diseases. Initial product applications may temporarily increase BOD level;
it is therefore advisable to provide sub-surface aeration to expedite the
establishment of the benefi cial microbial species. A minimum dissolved
oxygen level of 3% is required for their effective utilization.
NEW TECHNOLOGIES FOR MICROBIAL REMEDIATION
Microbial Mats
Microbial mats occur in nature as laminated heterotrophic and autotrophic
vertically stratifi ed communities typically dominated by cyanobacteria,
eukaryotic microalgae like diatoms, anoxygenic phototrophic bacteria
and sulphate reducing bacteria (D'amelio et al., 1989), but they can be
cultured on a large-scale and manipulated for a variety of functions. Their
physiological fl exibility includes anoxygenic and oxygenic photosynthesis,
inclusion of aerobes and anaerobes within the same matrix simultaneously
(Caumette et al., 1994). The functional uses of mats broadly cover the
areas of aquaculture and bioremediation. Regarding aquaculture, mats
were shown to produce protein, via nitrogen fi xation, and are capable