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Trees and Natural Fibers
Published in Antonio Paesano, Handbook of Sustainable Polymers for Additive Manufacturing, 2022
Alginic acid, or algin, is a polysaccharide that is present in the cell walls of brown algae and imparts structural properties. Algin is hydrophilic and forms a viscous gum when hydrated. Salts of algin with metals such as sodium and calcium are called alginates. Alginate is an attractive biomaterial for TE because it is biocompatible, slightly toxic, relatively inexpensive, and produces a mild and rapid formation of hydrogel (HG) (Lee and Mooney 2012), with the latter characteristic leading to stable geometry after printing. Brown algae contain an average of 40% alginate. Alginates are utilized by agricultural, biomedical (drug delivery, TE, wound healing), cosmetic, food, medical, paper, pharmaceutical (ingredient), and textile printing industries, with biomedical, medical, and pharmaceutical making up 20% of the global market. Cosmetic, food, and pharmaceutical industries primarily utilize alginates as thickeners and stabilizers. The price of alginates varies depending on its purity and applications: alimentary grade sodium alginate is USD 6.5−11/kg, while pharmaceutical grade is USD 13−15.5/kg. Global alginate market was USD 624 million in 2016, and is expected to grow at 2−3% per year. Pereira and João Cotas (2020) published a wide-ranging overview of alginates, from which some of above information were derived.
Immobilization of Biomolecules
Published in Anil Kumar Anal, Bionanotechnology, 2018
Alginic acid, a natural polymer, is a polyuronic acid extracted from seaweeds and is composed of varying proportions of 1-4 linked β-d-mannuronic (M) and α-l-guluronic acids (G). These residues are present in varying proportions depending on the sources of the alginic acid. It turned out that alginic acid (and its salts) is a block copolymer, containing both MM…and GG…homopolymer blocks and mixed blocks containing irregular sequences of M and G units (Atkins et al. 1973; Annison et al. 1983). The binding of divalent cations and subsequent gel formation is dependent on the composition and arrangement of the blocks of residues. In particular, gel strength is related to G content. The proportion of these segments varies between each species of kelp and imparts distinctly different properties to the final product. Depending on the specific species of kelp used in manufacturing, ratios of mannuronic acid to guluronic acid contents (M/G ratio) typically range from 0.4 to 1.9 (Orive et al. 2005; Orive et al. 2006). The GG blocks have preferential binding sites for divalent cations, such as Ca2+, and the bound ions can interact with other GG blocks to form linkages that lead to gel formation. On addition of sodium alginate solution to a calcium solution, interfacial polymerization is instantaneous with precipitation of calcium alginate followed by a more gradual gelation of the interior as calcium ions permeate through the alginate (Qi et al. 2008). Other than calcium, barium has also been tried and explored as cationic divalent for gelification of alginate. As barium is known to be toxic, concerns have been raised to using this ion as a cross-linking agent (WikstrÖm et al. 2008).
Dielectric Analysis of Different Natural and Synthetic Polymer Types
Published in Jose James, K.P. Pramoda, Sabu Thomas, Polymers and Multicomponent Polymeric Systems, 2019
Hugo Salazar, Pedro M. Martins, C.M. Costa, S. Lanceros-Méndez
Alginate is a biopolymer extracted from seaweeds (Figure 10.13), where it is present as a cell wall component, with structural functions similar to other biopolymers like agar and carrageenan. Alginate can be extracted from seaweeds through three different processes: the dissolution of the alginic acid present on seaweed biomass with an alkaline solution, precipitation of sodium alginate with calcium chloride and filtration, and purification and drying. Alginate is widely used in food applications, paper coating, textile printing paste, wound dressings, pharmaceuticals, and others [73] due to its gelling, thickening, and film-forming properties.
Use of Sargassum muticum algae as binder strengthening for raw earth mortar
Published in European Journal of Environmental and Civil Engineering, 2023
A. Graich, Y. EL Haloui, H. Rchid, R. Nmila, M. Siniti, I. Mrani, M. Monkade, M. Khaidar, A. Zradba
The addition of organic binders is arousing more and more interest, particularly polysaccharides, but the number of papers devoted to polysaccharides of algal origin is still rare in the field of building materials (Dove et al., 2016). These biopolymers, which are widely distributed in the cell walls of brown algae (or pheophyceae), can consist of 20 to 60% in the dry matter according to (Rehm, 2009). 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. They are extracted in the form of alginic acid by dilution in an acid. The alginate copolymer consists of a succession of α–L-guluronic (G) and β–D–mannuronic (M) base monomers. The ratio (G/M) between these two monomers depends on the nature of the source algae.
Recent advances in microbeads-based drug delivery system for achieving controlled drug release
Published in Journal of Biomaterials Science, Polymer Edition, 2023
Zafar Khan, Mohammed A.S. Abourehab, Neha Parveen, Kanchan Kohli, Prashant Kesharwani
These are isolated from brown sea wood using a dilute alkaline solution which solubilizes the alginic acid present in alginates [44]. Alginic acid is made up of linear polymer of D-mannuronic acid and L-guluronic acid that are arranged as blocks in the polymeric chain. Alginic acid when reacts with sodium hydroxide gets converted into sodium alginate[45]. Naturally occurring alginate polymers possess several favorable properties like its accessibility, pH sensitive hydrogels forming capability and the lack of toxicity [46]. Sodium and calcium salts of alginic acid are considered as non-hazardous and biocompatible. Over 200 different grades are available commercially. A variety of impurities including heavy metals, proteins and endotoxins were present in alginates as they are naturally obtained [47]. For parenteral use these impurities should be removed. Ultrapure grades of alginates have low pyrogenicity and combination with other drugs as implants may be used [48].
Impact of advanced extraction technologies and characterization of freeze-dried brown seaweed polysaccharides
Published in Drying Technology, 2020
K. R. Karthika Parvathy, M. Ajanth Praveen, P. Balasubramanian, Bibekanand Mallick
The obtained 1H NMR peaks (Figure 4d) are correlated with previously reported data. The spectra at 4.703 ppm and chemical shift at 3.5 to 3.7 ppm revealed the peaks correspond to laminarin and signal enhancement derived from mannitol, which is a characteristic of brown algae. Polysaccharides of brown seaweeds majorly constitute laminarin, mannitol and uronic composition of alginic acid.[51,52] Ulvan (Sulfated glucuronorhamnoxylan) composed of 4-linked l-rhamnose-3-sulfate and d-xylose residues (ulvobiose) with monomeric d-glucuronic acid or d-glucuronic acid-3-sulfate on O-2 of some l-rhamnose-3-sulfate units as the side chains alternatively.[53]