Alginic acid

Last updated
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).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)
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. When the alginic acid binds with sodium and calcium ions, the resulting 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]

Alginate was discovered by British chemical scientist E. C. C. Stanford in 1881, and he patented an extraction process for it in the same year. [4] The alginate was extracted, in the original patent, by first soaking the algae in water or diluted acid, then extracting the alginate by soaking it in sodium carbonate, and finally precipitating the alginate from solution. [5] [ better source needed ]

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.[ citation needed ]

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. [6]

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. [7]

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. [8]

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. [9] The conventional process involves large amounts of reagents and solvents, as well as time-consuming steps. [4] Simpler and newer techniques, such as microwave-assisted extraction, ultrasound, high pressure, pressurized fluid extraction, and enzyme-assisted extraction, are the subject of research. [4]

The most common, conventional extraction process involves six steps: pre-treatment of the algal biomass, acid treatment, alkaline extraction, precipitation, bleaching, and drying. [4] Pre-treatments mainly aim at either breaking the cell wall to help extract the alginate, or removing other compounds and contaminants from the algae. [4] Drying is of the first kind, also helping to prevent bacterial growth; algae which is dried is also usually powdered to expose more surface area. [4] Common treatments to remove contaminants include treatments with ethanol and formaldehyde, the latter of which is very common; ethanol solutions help remove compounds bonded to the alginate, and formaldehyde solutions help prevent enzymatic or microbial reactions. [4]

The algae is then treated with an acidic solution to help disrupt cell walls, which converts the alginate salts into insoluble alginic acid; a subsequently applied alkaline solution (pH 9-10), usually sodium carbonate, converts it back into water-soluble sodium alginate, which is then precipitated. [4] It is also possible to extract the alginate directly with an alkaline treatment, but this is less common. [4]

Alginic acid is usually precipitated, through different techniques, with either an alcohol (usually ethanol), calcium chloride, or hydrochloric acid. [4] After the alginin is precipitated into a fine paste, it is dried, ground to the desired grain size, and finally purified through a variety of techniques. [4] Commercial alginate for biomedical and pharmaceutical use is extracted and purified through more rigorous techniques, but these are trade secrets. [4]

Derivatives

Various alginate-based materials can be produced, including porous scaffold material, alginate hydrogel, nonwoven fabric, and alginate membranes. [10] Techniques used to produce these include ion cross-linking, microfluidic spinning, freeze drying, wet spinning, and immersive centrifugal jet spinning. [10]

Calcium salt[ clarification needed ] can be released in drops into a calcium alginate solution to induce ionic cross-linking, which produces the hydrogel. Freeze-drying the hydrogel to eliminate water produces the porous scaffold material. [10]

Wet spinning consists of extruding an alginate solution from a spinneret into a calcium salt solution to induce ionic cross-linking (forming the gel), and then drawing the fibers out of the bath with draft rollers. Microfluidic spinning, a simpler and more eco-friendly implementation of the process, involves introducing calcium salt flows flowing alongside and touching a central "core" flow of alginate. These flows form a "sheath". The fiber then emerges from the core flow. This technique can be used to produced shaped and grooved fibers. [10]

Preparation of the alginate nonwoven fabric by the acupuncture technique Alginate nonwoven fabric production.png
Preparation of the alginate nonwoven fabric by the acupuncture technique

Alginate fiber, which is used in fabric, is usually produced through either microfluidic spinning or wet spinning, or electrospinning to obtain thinner fibers. [10] The fabric, which can be used in wound dressing and other applications, is produced by carding and then needle punching [ clarification needed ] the fibers. [10]

Uses

As of 2022 alginate had become one of the most preferred materials as an abundant natural biopolymer. [10] It is particularly useful as a biomaterial because of its nontoxicity, hygroscopicity, and biocompatibility, and can imitate local bioenvironments; its degradation product can be easily cleared by the kidneys. [10]

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.[ citation needed ]

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. [11] [12] Sodium alginate is mixed with soybean protein to make meat analogue. [13]

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

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

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. [14]

Calcium alginate is used in different types of medical products, including skin wound dressings to promote healing, [15] [16] 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. [17] Alginate hydrogel is a common biomaterial for bio-fabrication of scaffolds and tissue regeneration. [18]

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. [19] Thiolated alginates are used as in situ gelling hydrogels, [20] and are under preliminary research as possible mucoadhesive drug delivery systems. [21] Alginate hydrogels may be used for drug delivery, exhibiting responses to pH changes, temperature changes, redox, and the presence of enzymes. [22]

See also

Related Research Articles

<span class="mw-page-title-main">Biopolymer</span> Polymer produced by a living organism

Biopolymers are natural polymers produced by the cells of living organisms. Like other polymers, biopolymers consist of monomeric units that are covalently bonded in chains to form larger molecules. There are three main classes of biopolymers, classified according to the monomers used and the structure of the biopolymer formed: polynucleotides, polypeptides, and polysaccharides. The Polynucleotides, RNA and DNA, are long polymers of nucleotides. Polypeptides include proteins and shorter polymers of amino acids; some major examples include collagen, actin, and fibrin. Polysaccharides are linear or branched chains of sugar carbohydrates; examples include starch, cellulose, and alginate. Other examples of biopolymers include natural rubbers, suberin and lignin, cutin and cutan, melanin, and polyhydroxyalkanoates (PHAs).

<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 hemicellulose and chitin.

<span class="mw-page-title-main">Pectin</span> Structural carbohydrate in the cell walls of land plants and some algae

Pectin is a heteropolysaccharide, a structural polymer contained in the primary lamella, in the middle lamella, and in the cell walls of terrestrial plants. The principal chemical component of pectin is galacturonic acid which was isolated and described by Henri Braconnot in 1825. Commercially produced pectin is a white-to-light-brown powder, produced from citrus fruits for use as an edible gelling agent, especially in jams and jellies, dessert fillings, medications, and sweets; as a food stabiliser in fruit juices and milk drinks, and as a source of dietary fiber.

<span class="mw-page-title-main">Carrageenan</span> Natural linear sulfated polysaccharide

Carrageenans or carrageenins are a family of natural linear sulfated polysaccharides. They are extracted from red edible seaweeds. Carrageenans are widely used in the food industry, for their gelling, thickening, and stabilizing properties. Their main application is in dairy and meat products, due to their strong binding to food proteins. Carrageenans have emerged as a promising candidate in tissue engineering and regenerative medicine applications as they resemble animal glycosaminoglycans (GAGs). They are used for tissue engineering, wound coverage, and drug delivery.

<span class="mw-page-title-main">Hydrogel</span> Soft water-rich polymer gel

A hydrogel is a biphasic material, a mixture of porous, permeable solids and at least 10% by weight or volume of interstitial fluid composed completely or mainly by water. In hydrogels the porous permeable solid is a water insoluble three dimensional network of natural or synthetic polymers and a fluid, having absorbed a large amount of water or biological fluids. These properties underpin several applications, especially in the biomedical area. Many hydrogels are synthetic, but some are derived from nature. The term 'hydrogel' was coined in 1894.

<span class="mw-page-title-main">Chitosan</span> Chemical compound

Chitosan is a linear polysaccharide composed of randomly distributed β-(1→4)-linked D-glucosamine and N-acetyl-D-glucosamine. It is made by treating the chitin shells of shrimp and other crustaceans with an alkaline substance, such as sodium hydroxide.

<span class="mw-page-title-main">Thickening agent</span> Increases the viscosity of a liquid without altering its other properties

A thickening agent or thickener is a substance which can increase the viscosity of a liquid without substantially changing its other properties. Edible thickeners are commonly used to thicken sauces, soups, and puddings without altering their taste; thickeners are also used in paints, inks, explosives, and cosmetics.

<span class="mw-page-title-main">Sodium polyacrylate</span> Anionic polyelectrolyte polymer

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<span class="mw-page-title-main">Superabsorbent polymer</span> Polymers that absorb and retain extremely large amounts of liquid

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<span class="mw-page-title-main">Mannuronate-specific alginate lyase</span>

The enzyme mannuronate-specific alginate lyase catalyzes the degradation of alginate into various monosaccharide and polysaccharide products:

<span class="mw-page-title-main">Calcium alginate</span> Chemical compound

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Vitaliy Khutoryanskiy FRSC FAPS is a British and Kazakhstani scientist, a Professor of Formulation Science and a Royal Society Industry Fellow at the University of Reading. His research focuses on polymers, biomaterials, nanomaterials, drug delivery, and pharmaceutical sciences. Khutoryanskiy has published over 200 original research articles, book chapters, and reviews. His publications have attracted > 12000 citations and his current h-index is 53. He received several prestigious awards in recognition for his research in polymers, colloids and drug delivery as well as for contributions to research peer-review and mentoring of early career researchers. He holds several honorary professorship titles from different universities.

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. 1 2 3 4 5 6 7 8 9 10 11 12 Bojorges, Hylenne; López-Rubio, Amparo; Martínez-Abad, Antonio; Fabra, María José (2023-10-01). "Overview of alginate extraction processes: Impact on alginate molecular structure and techno-functional properties". Trends in Food Science & Technology. 140: 104142. doi:10.1016/j.tifs.2023.104142. hdl: 10261/336757 . ISSN   0924-2244.
  5. ↑ Pereira, Leonel; Cotas, João (2020-02-05), "Introductory Chapter: Alginates - A General Overview", Alginates - Recent Uses of This Natural Polymer, IntechOpen, ISBN   978-1-78985-642-2 , retrieved 2024-08-06
  6. ↑ "Alginates" (PDF). Agricultural Marketing Service, US Department of Agriculture. 5 February 2015. Retrieved 1 March 2018.
  7. ↑ 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
  8. ↑ 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.
  9. ↑ FAO Fisheries Technical Paper, 2003
  10. 1 2 3 4 5 6 7 8 Zhang, Xiaolin; Wang, Xinran; Fan, Wei; Liu, Yi; Wang, Qi; Weng, Lin (2022-08-08). "Fabrication, Property and Application of Calcium Alginate Fiber: A Review". Polymers. 14 (15): 3227. doi: 10.3390/polym14153227 . ISSN   2073-4360. PMC   9371111 . PMID   35956740.
  11. ↑ "What is Sodium Alginate (E401) in food? Properties, Uses, Safety". FOODADDITIVES. 14 May 2020.
  12. ↑ 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.
  13. ↑ 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.
  14. ↑ 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.
  15. ↑ 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.
  16. ↑ 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.
  17. ↑ 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.
  18. ↑ 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.
  19. ↑ 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.
  20. ↑ 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.
  21. ↑ 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.
  22. ↑ 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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