Polysaccharides in aquatic disease management

The article introduces the effects of some polysaccarides that can be used to control diseases in aquatic animals, including: Carrageenan, Sodium alginate, Ergosan, Laminaran, β-glucan, Chitosan, Fucoidan, Alginic acid.
 
Polysaccarides can be used to control diseases in aquatic animals.
Using an immune response to control diseases in aquatic animals
Disease is one of the main threats to the aquaculture industry. Traditionally, the way to control the disease is usually to use antibiotics or chemical disinfectants, but they are not recommended because of the presence of resistant strains as well as the accumulation of drug residues in environment and other organisms. Although vaccines are very effective against fish diseases, they are quite expensive, time consuming and stressful for the fish. In this context, a naturally occurring immune response agent that helps fish and shrimp increase their resistance to pathogens has begun to be widely used in aquaculture. The use of immune response agents has been increasingly noticed because they are less toxic, environmentally friendly, highly bioactive. They are important for scaly fish and shellfish.
 
General structural formula of polysaccharide.
Marine polysaccharide, an immune response that helps control pathogens
In recent years, scientists have been paying attention to the effects of polysaccharide (a high molecular carbohydrate molecule consisting of long chains of monosaccharide units linked together by glycosidic bonds) derived from the ocean. Marine polysaccharide, as an antibiotic treatment or production agent, is less toxic and highly bioavailable. Polysaccharides will generally be separated based on their distinct origin (from plants, animals and bacteria).
In fish, it has been shown that certain substances absorbed from seaweed, mainly polysaccharides, may affect the activity of certain components of the immune system and increase the body's immunity. with any pathogen. In carp, if injected into the abdominal cavity Carrageenan - a polysaccharide abundant in red seaweed, will increase phagocytic activity and resistance against infection. In addition, Sodium alginate also known as polysaccharide salt helps accelerate the phagocytic movement in the adrenal carp to the abdominal cavity and increases phagocytic capacity when V. anguillarum infection. In addition, Ergosan - a polysaccharide extracted from seaweed, contains alginic acid which will increase the proportion of neutrophilic granulocytes, phagocytic levels, oxidants and the expression of interleukins (cytokine group, which is a substance mediator between cells in the body) in rainbow trout. Other polysachharides such as laminaran and β-glucan are absorbed from the brown algae Laminaria hyperborea, increasing the activity of macrophages on salmon.
Similarly, Chitosan (β- (1, 4) -2-amino-2-deoxy-D-glucose) is a polymer cation obtained from deacetylation (the process of removing acetyl groups from compounds) of chitin. Chitosan polysaccharide has the effect of promoting immune activity in fish and shellfish. For example, in vannamei shrimp, the injection of chitin or chitosan may help increase the viability of V. alginolyticus by promoting increased blood cells, oxidants and phagocytic activity. Some reports show that the stimulation of the immune activity of chitin or chitosan is often found in rainbow trout, rainbowfish, yellow bream. Another study by Gopalakannan and Arul compared chitin, chitosan and levamisole in carp against the Aeromonas hydrophila infection in the pond, showing that the group fed chitosan boosted the innate immune system and survival rates in carp. In addition, Niu also said that chitin and its derivatives (chitosan, chitosan oligosaccharides and N-acetyl-D-glucosamine) stimulate growth, are antioxidants and antioxidant status in black tiger shrimp.
Chitin deacetylation process to produce chitosan.
Fucoidan (sulfated polysaccharides) is commonly found in brown algae and some invertebrates such as sea cucumbers and sea urchins. They consist mainly of fucose and sulfate in small amounts of galactose, xylose, mannose, and uronic acids.
Fucoidan has diverse biological effects such as anticoagulant, anti-cancer, immunomodulatory and anti-inflammatory drugs. From other potential biological activities of fucoidan, Chotigeat has conducted experiments on white spot antiviral activity of raw fucoidan extracted from Sargassum polycystum (brown algae). In addition, when feeding black tiger shrimp fucoidan 200mg / kg body weight per day, the survival rate reached 93%. In addition, they prevent the growth of harmful bacteria such as Vibrio harveyi, Staphylococcus aureus and Escherichia coli. Similarly, Immaunel said the fucoidan from Sargassum wightii reduces the death rate by up to 68.06% and enhances immune parameters such as: THC (blood cell count), enzyme activity prophenoloxidase, oxidants, enzyme superoxide dismutase (an enzyme that neutralizes free radicals) and phagocytic activity. Sivagnanavelmurugan also used fucoidan from Sargassum Wightii to feed Artemia larvae (400mg / L) and Artemia for black tiger shrimp to reduce mortality to 61.6% and fight white spot infection. In the experiments of Marudhupandi and Ajith Kumar, the fucoidan extracted from Turbinaria showed antibacterial potential in marine fish diseases such as Aeromonas hydrophila, Enterobacter sp., Pseudomonas aeruginosa, treptococcus sp., Escherichia coli, Vibrio parahaemolyticus, Vibrio alginolyticus, Vibrio cholerae, Yersinia enterocolitica and Proteus sp. Marlowe also investigated the immunomodulatory abilities of alginic and fucoidan, both of which are derived from brown algae. Kitikiew recently said that fucoidan has the innate immunity of whiteleg shrimp and its resistance to V. alginolyticus.
The composition of Fucoidan.
Alginic acid is a well-known anionic polysaccharide and is distributed mainly in the cell walls of brown algae. Alginic acid is a linear copolymer with homopolymeric blocks of (1-4) -D-mannuronate binding (M) and its C-5 epime residue α-L-g
uluronate (G), respectively, covalent bonds with each other in different chains or blocks. The monomers may appear in homogeneous masses of consecutive G residue (G mass), consecutive M residues (M mass) or alternating M and G residues (MG mass).
Only some alginic acid immune activities are published. In fish, alginic acid increases the activity of adrenal phagocytic cells and their movement from the injection site by increasing production of chemical factors and their sensitivity. Ergosan abdominal sinus injection (containing 1% alginic acid) will increase neutrophils, phagocytic levels and oxygen stimulating activity in Salmon Van as well as the expression of interleukins (IL-1b) and chemokines. However, it has no effect on lysozyme and works against protease when beyond the 7-day period. Alginic acid and Fucoidan can modulate cellular reactions, especially oxidants and adrenal leukocytes in Atlantic cod. Thus, from the above grounds, polysaccharides can be used to develop therapies such as immune response or aquatic disease control drugs.
Updated on 23-12-2019
According to Thangapandi Marudhupandi and Dhinakarasamy Inbakandan.

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