Alginic acid

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Alginic acid
Alginsaure.svg
Names
Other names
Alginic acid; E400; [D-ManA(β1→4)L-GulA(α1→4)]n
Identifiers
ChemSpider
  • None
ECHA InfoCard 100.029.697 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 232-680-1
E number E400 (thickeners, ...)
UNII
Properties
(C6H8O6)n
Molar mass 10,000 – 600,000
AppearanceWhite to yellow, fibrous powder
Density 1.601 g/cm3
Acidity (pKa)1.5–3.5
Pharmacology
A02BX13 ( WHO )
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Macrocystis pyrifera, the largest species of giant kelp Giantkelp2 300.jpg
Macrocystis pyrifera , the largest species of giant kelp

Alginic acid, also called algin, is a naturally occurring, edible polysaccharide found in brown algae. It is hydrophilic and forms a viscous gum when hydrated. With metals such as sodium and calcium, its salts are known as alginates. Its colour ranges from white to yellowish-brown. It is sold in filamentous, granular, or powdered forms.

Contents

It is a significant component of the biofilms produced by the bacterium Pseudomonas aeruginosa , a major pathogen found in the lungs of some people who have cystic fibrosis. [1] The biofilm and P. aeruginosa have a high resistance to antibiotics, [2] but are susceptible to inhibition by macrophages. [3]

Structure

Alginic acid is a linear copolymer with homopolymeric blocks of (1→4)-linked β-D-mannuronate (M) and α-L-guluronate (G) residues, respectively, covalently linked together in different sequences or blocks. The monomers may appear in homopolymeric blocks of consecutive G-residues (G-blocks), consecutive M-residues (M-blocks) or alternating M and G-residues (MG-blocks). α-L-guluronate is the C-5 epimer of β-D-mannuronate.

Forms

Alginates are refined from brown seaweeds. Throughout the world, many of the Phaeophyceae class brown seaweeds are harvested to be processed and converted into sodium alginate. Sodium alginate is used in many industries including food, animal food, fertilisers, textile printing, and pharmaceuticals. Dental impression material uses alginate as its means of gelling. Food grade alginate is an approved ingredient in processed and manufactured foods. [4]

Brown seaweeds range in size from the giant kelp Macrocystis pyrifera which can be 20–40 meters long, to thick, leather-like seaweeds from 2–4 m long, to smaller species 30–60 cm long. Most brown seaweed used for alginates are gathered from the wild, with the exception of Laminaria japonica , which is cultivated in China for food and its surplus material is diverted to the alginate industry in China.

Alginates from different species of brown seaweed vary in their chemical structure, resulting in different physical properties of alginates. Some species yield an alginate that gives a strong gel, another a weaker gel, some may produce a cream or white alginate, while others are difficult to gel and are best used for technical applications where color does not matter. [5]

Commercial grade alginate is extracted from giant kelp Macrocystis pyrifera , Ascophyllum nodosum , and types of Laminaria . Alginates are also produced by two bacterial genera Pseudomonas and Azotobacter , which played a major role in the unravelling of its biosynthesis pathway. Bacterial alginates are useful for the production of micro- or nanostructures suitable for medical applications. [6]

Sodium alginate (NaC6H7O6) is the sodium salt of alginic acid. Sodium alginate is a gum.

Potassium alginate (KC6H7O6) is the potassium salt of alginic acid.

Calcium alginate (CaC12H14O12) is the calcium salt of alginic acid. It is made by replacing the sodium ion in sodium alginate with a calcium ion (ion exchange).

Production

The manufacturing process used to extract sodium alginates from brown seaweed fall into two categories: 1) calcium alginate method and, 2) alginic acid method.[ clarification needed ]

Chemically the process is simple, but difficulties arise from the physical separations required between the slimy residues from viscous solutions and the separation of gelatinous precipitates that hold large amounts of liquid within their structure, so they resist filtration and centrifugation. [7]

Uses

Alginate absorbs water quickly, which makes it useful as an additive in dehydrated products such as slimming aids, and in the manufacture of paper and textiles.

Alginate is also used for waterproofing and fireproofing fabrics, in the food industry as a thickening agent for drinks, ice cream, cosmetics, as a gelling agent for jellies, known by the code E401 and sausage casing. [8] [9] Sodium alginate is mixed with soybean protein to make meat analogue. [10]

Alginate is used as an ingredient in various pharmaceutical preparations, such as Gaviscon, in which it combines with bicarbonate to inhibit gastroesophageal reflux.

Sodium alginate is used as an impression-making material in dentistry, prosthetics, lifecasting, and for creating positives for small-scale casting.

Sodium alginate is used in reactive dye printing and as a thickener for reactive dyes in textile screen-printing.[ citation needed ] Alginates do not react with these dyes and wash out easily, unlike starch-based thickeners. It also serves as a material for micro-encapsulation. [11]

Calcium alginate is used in different types of medical products, including skin wound dressings to promote healing, [12] [13] and may be removed with less pain than conventional dressings.[ citation needed ]

Alginate hydrogels

In research on bone reconstruction, alginate composites have favorable properties encouraging regeneration, such as improved porosity, cell proliferation, and mechanical strength. [14] Alginate hydrogel is a common biomaterial for bio-fabrication of scaffolds and tissue regeneration. [15]

By the covalent attachment of thiol groups to alginate high in situ gelling and mucoadhesive properties can be introduced. The thiolated polymer (thiomer) forms disulfide bonds within its polymeric network and with cysteine-rich subdomains of the mucus layer. [16] Thiolated alginates are used as in situ gelling hydrogels, [17] and are under preliminary research as possible mucoadhesive drug delivery systems. [18] Alginate hydrogels may be used for drug delivery, exhibiting responses to pH changes, temperature changes, redox, and the presence of enzymes. [19]

See also

Related Research Articles

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<span class="mw-page-title-main">Polysaccharide</span> Long carbohydrate polymers such as starch, glycogen, cellulose, and chitin

Polysaccharides, or polycarbohydrates, are the most abundant carbohydrates found in food. They are long-chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with water (hydrolysis) using amylase enzymes as catalyst, which produces constituent sugars. They range in structure from linear to highly branched. Examples include storage polysaccharides such as starch, glycogen and galactogen and structural polysaccharides such as cellulose and chitin.

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References

  1. ↑ Davies, JC (2002). "Pseudomonas aeruginosa in cystic fibrosis: pathogenesis and persistence". Paediatric Respiratory Reviews. 3 (2): 128–34. doi:10.1016/S1526-0550(02)00003-3. ISSN   1526-0542. PMID   12297059.
  2. ↑ Boyd, A; Chakrabarty, AM (1995). "Pseudomonas aeruginosa biofilms: role of the alginate exopolysaccharide". Journal of Industrial Microbiology. 15 (3): 162–8. doi: 10.1007/BF01569821 . ISSN   0169-4146. PMID   8519473. S2CID   42880806.
  3. ↑ Leid, JG; Willson, CJ; Shirtliff, ME; Hassett, DJ; Parsek, MR; Jeffers, AK (1 November 2005). "The exopolysaccharide alginate protects Pseudomonas aeruginosa biofilm bacteria from IFN-gamma-mediated macrophage killing" (PDF). Journal of Immunology. 175 (11): 7512–8. doi: 10.4049/jimmunol.175.11.7512 . ISSN   0022-1767. PMID   16301659. S2CID   1011606.
  4. ↑ "Alginates" (PDF). Agricultural Marketing Service, US Department of Agriculture. 5 February 2015. Retrieved 1 March 2018.
  5. ↑ FAO fisheries technical paper 441, Tevita Bainiloga Jnr, School of Chemistry, University College, University of New South Wales and Australian Defence Force Academy Canberra Australia
  6. ↑ Remminghorst and Rehm (2009). "Microbial Production of Alginate: Biosynthesis and Applications". Microbial Production of Biopolymers and Polymer Precursors. Caister Academic Press. ISBN   978-1-904455-36-3.
  7. ↑ FAO Fisheries Technical Paper, 2003
  8. ↑ "What is Sodium Alginate (E401) in food? Properties, Uses, Safety". FOODADDITIVES. 14 May 2020.
  9. ↑ Qin, Yimin (17 July 2018). Bioactive Seaweeds for Food Applications. doi:10.1016/C2016-0-04566-7. ISBN   978-0-12-813312-5. Archived from the original on 2023-11-09.
  10. ↑ Arasaki, Seibin; Arasaki, Teruko (January 1983). Low Calorie, High Nutrition Vegetables from the Sea (1st ed.). Tokyo, Japan: Japan Publications, Inc. p. 35. ISBN   0-87040-475-X.
  11. ↑ Aizpurua-Olaizola, Oier; Navarro, Patricia; Vallejo, Asier; Olivares, Maitane; Etxebarria, Nestor; Usobiaga, Aresatz (2016-01-01). "Microencapsulation and storage stability of polyphenols from Vitis vinifera grape wastes". Food Chemistry. 190: 614–621. doi:10.1016/j.foodchem.2015.05.117. PMID   26213018.
  12. ↑ Lansdown AB (2002). "Calcium: a potential central regulator in wound healing in the skin". Wound Repair Regen. 10 (5): 271–85. doi:10.1046/j.1524-475x.2002.10502.x. PMID   12406163. S2CID   10092676.
  13. ↑ Stubbe, Birgit; Mignon, Arn; Declercq, Heidi; Vlierberghe, Sandra Van; Dubruel, Peter (2019). "Development of Gelatin-Alginate Hydrogels for Burn Wound Treatment". Macromolecular Bioscience. 19 (8): 1900123. doi:10.1002/mabi.201900123. ISSN   1616-5195. PMID   31237746. S2CID   195355185.
  14. ↑ Venkatesan, J; Bhatnagar, I; Manivasagan, P; Kang, K. H.; Kim, S. K. (2015). "Alginate composites for bone tissue engineering: A review". International Journal of Biological Macromolecules. 72: 269–81. doi:10.1016/j.ijbiomac.2014.07.008. PMID   25020082.
  15. ↑ Rastogi, Prasansha; Kandasubramanian, Balasubramanian (2019-09-10). "Review of alginate-based hydrogel bioprinting for application in tissue engineering". Biofabrication. 11 (4): 042001. Bibcode:2019BioFa..11d2001R. doi:10.1088/1758-5090/ab331e. ISSN   1758-5090. PMID   31315105. S2CID   197543168.
  16. ↑ Leichner, C; Jelkmann, M; Bernkop-Schnürch, A (2019). "Thiolated polymers: Bioinspired polymers utilizing one of the most important bridging structures in nature". Adv Drug Deliv Rev. 151–152: 191–221. doi:10.1016/j.addr.2019.04.007. PMID   31028759. S2CID   135464452.
  17. ↑ Xu, G; Cheng, L; Zhang, Q; Sun, Y; Chen, C; Xu, H; Chai, Y; Lang, M (2016). "In situ thiolated alginate hydrogel: Instant formation and its application in hemostasis". J Biomater Appl. 31 (5): 721–729. doi:10.1177/0885328216661557. PMID   27485953. S2CID   4267830.
  18. ↑ Kassem, AA; Issa, DA; Kotry, GS; Farid, RM (2017). "Thiolated alginate-based multiple layer mucoadhesive films of metformin for intra-pocket local delivery: in vitro characterization and clinical assessment". Drug Dev. Ind. Pharm. 43 (1): 120–131. doi:10.1080/03639045.2016.1224895. PMID   27589817. S2CID   25076932.
  19. ↑ Abasalizadeh, Farhad; Moghaddam, Sevil; Alizadeh, Effat; Fazljou, Mohammad; Torbati, Mohammadali; Akbarzadeh, Abolfazl (13 March 2020). "Alginate-based hydrogels as drug delivery vehicles in cancer treatment and their applications in wound dressing and 3D bioprinting". Journal of Biological Engineering. 14 (8): 8. doi: 10.1186/s13036-020-0227-7 . PMC   7069202 . PMID   32190110.
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