Probiotics in Aquaculture
28 May 2021
Aquaculture is the controlled process of cultivating marine animals like fish, crustaceans, molluscs, especially for human consumption. Aquaculture is the fastest growing food producing agricultural sector that allows a selective increase in the production of species used for human consumption, industry or sport fishing . Infectious disease is a major limitation to the sustainable development of aquaculture sector. A major tool in prevention of diseases in marine animals is the use of antibiotics but it has been proven ineffective gradually as the pathogens can develop resistance towards the antibiotics with time either through mutation, or horizontal gene transfer (HGT) in the environment, via natural transformation, transduction, or conjugation . Probiotic is one of the known alternatives that can lessen the dependence of the aquaculture industry on antibiotics. The use of antibiotics in aquaculture systems can create serious problems, economic as well as health related .
The World Health Organization defines probiotics as “live microorganisms which when administered in adequate amounts confer a health benefit on the host” (FAO/WHO, 2002).
Probiotics were initially used for disease control but their use in aquaculture has now extended to improving fish growth and reproduction by adding them to the water body or the fish feed. The mechanism of action of probiotics focuses on improving the quality of rearing environment, protecting fish from biological hazard and modulating physiological processes that promote the health status of the marine animal in culture. They are able to persist in the digestive tract as they can tolerate high acid and bile salts concentration.
Mode of action of probiotic includes production of inhibitory compounds, competition for chemicals also as available energy, competition for adhesion sites, immune reaction enhancement, water quality improvement and interaction with phytoplankton, source of macro- and micronutrients, and contribution to digestion enzymatically .
The benefits observed within the supplementation of probiotics in aquaculture include,
1. Improvement of the nutritional value of food;
2. Enzymatic contribution to digestion;
3. Pathogen inhibition;
4. Growth promoting factors;
5. Immune response improvement; and
6. Farming water quality improvement .
Probiotics in aquaculture practices
The majority of bacteria are transient in the intestine of aquatic species due to constant intake of water and food along with the microorganisms present in them. Apart from the potentially pathogenic bacteria like Salmonella, Listeria, and E. coli, probiotic bacteria and other microorganisms have also been identified in the gastrointestinal tract of aquatic animals that include the gram-positive bacteria like Bacillus, Carnobacterium, Enterococcus, and several species of Lactobacillus, gram negative, facultative anaerobes like Vibrio and Pseudomonas, also certain fungi, yeasts, and algae of the genera Debaryomyces, Saccharomyces, and Tetraselmis, respectively .
3. Selection of probiotics
For a microorganism to be used as a probiotic, its isolation and characterization and testing is necessary to certify its probiotic efficiency.
First, the source of microorganism should be selected then work should be carried out for its isolation and identification by means of selective culture.
Then the colonies of interest from a new culture should be used for conducting in vitroevaluations (inhibition of pathogens, pathogenicity to target species, resistance conditions of host among others).
In vivo supplementation, small and enormous scale, are further administered to see if there are any real benefits to the host.
Finally, the probiotic presenting significantly satisfactory result are often produced commercially and then utilized .
On the basis of product, the probiotic market is assigned into three categories, namely, probiotic food & beverages, probiotic dietary supplements, and animal feed probiotics. The food and beverage is further segmented into dairy, non-dairy, cereals, baked food, fermented meat, and dry food probiotics.
By ingredient, the market can be broadly categorised into bacteria and yeast. The bacteria can be further classified into Lactobacilli, Bifidobacterium, Streptococcus, and others, while yeast can be further classified into Saccharomyces boulardii and others.
On the basis of end use, the market has been broadly divided into human and animal probiotics.[a].
The world probiotic market is expected to collect $57.4 billion by 2022, registering a CAGR (Compound Annual Growth Rate) of 7.7% during the forecast period 2016-2022. The key players operating in this market comprises of BioGaia AB, Danone, Chr. Hansen Holding A/S, Yakult Honsha Co. Ltd., Probi AB, Lifeway Foods, Inc., Nestle S.A., Ganeden, Inc., E. I. du Pont de Nemours and Company and Protexin. [a]
Brands that exist now in Indian probiotic industry are Nestle, Amul, Yakult Danone and Mother Dairy alongside other minor players operating in several regions in their own capacities.[b]
Table 2. List of probiotic microorganisms[d]
There should be a minimum 106 CFU mL-1of live probiotic bacteria at the time of consumption. Research has shown that probiotics (108 –109 CFU mL-1) can regulate gut microbiota, improve immune system, reduce symptoms of lactose intolerance as well as prevent and/or treat gastrointestinal infections .
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4. Verschuere, L., Geert Rombaut, Patrick Sorgeloos and Willy Verstraete. 2000. Probiotic Bacteria as Biological Control Agents in Aquaculture, 64(4):655-671.
5. Rafael Vieira de Azevedo and Luís Gustavo Tavares Braga. Use of Probiotics in Aquaculture.
6. Syngai G. G. & Ragupathi Gopi & Rupjyoti Bharali & Sudip Dey & G. M. Alagu Lakshmanan & Giasuddin Ahmed. 2016. Probiotics - the versatile functional food ingredients 53(2):921–933.
7. Marinova, V. Y., Iliyana Kirilova Rasheva, Yoana Krasimirova Kizheva, Yordanka Dimitrova Dermenzhieva & Petya Koitcheva Hristova. 2019. Microbiological quality of probiotic dietary supplements, 33(1):834-841.