THE ROLE OF BACTERIA IN BIOFLOC

Microbial role in bioflocsystem


1. Bioremediation (In-situ) of toxic ammonia: The biofloc system maintains adequate water quality especially toxic nitrogen metabolites. At higher C: N ratio, bacteria immobilize toxic ammonia into microbial protein within a few hours, when assimilating carbon, as compared to slow conventional nitrification process which takes a month to get established.


2. Biocontrol agent: Shrimps/fishes are healthiest and grow best in aquaculture systems that have adequate levels of algae, bacteria and other natural microbiota. Probiotics are viable microbial cells and have beneficial effect on the health of shrimp/fish by stimulation of immune system and microbial equilibrium in the gut and by inhibition of pathogenic microbes. Microbes store poly-β-hydroxybutyrate (PHB) as a stored product of carbon and energy. Its synthesis is stimulated in the condition of limited nitrogen supply and with excess carbon supplementation. Condition available in biofloc system thus enhances its production. The PHB particles offer preventive and curative protection in Artemia nauplii against luminescent pathogenic Vibrio campbelli. This indicates that biofloc can serve as a novel strategy for disease management on long term basis.


3. Healthy supplementary food: The protein content of bacteria is almost 60%. Therefore, its consumption becomes an alternate source of protein for aquatic animals like shrimp.


4. Probiotics and immunostimulant: Biofloc is a microbial consortium, which has a large number of

bacteria, which could play a powerful role in digestive enzyme secretion and as an immunostimulant. Biofloc formation starts 36 hours after addition of carbon source when the bacterial count reaches 10^6-10^7cfu. The increase in C: N ratio reduced the total ammonia nitrogen level. The CN20 was most effective while CN5 was least effective in reducing ammonia level. This corresponded to increased biofloc volume and the highest floc volume was observed in C/N=20 while the least was observed at C/N=5. Integration of substrate with biofloc system has profound effect on growth performance and immunity improvement in juvenile and sub-adult stages of shrimp/Fish.

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