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Algae as a Source of Polysaccharides and Potential Applications
Published in Sanjeet Mehariya, Shashi Kant Bhatia, Obulisamy Parthiba Karthikeyan, Algal Biorefineries and the Circular Bioeconomy, 2022
Sonal Tiwari, E Amala Claret, Vikas S. Chauhan
Agar is a large complex heteropolysaccharide made of two subunits, namely agarose and agaropectin. Overall, it is a polymer of repeating disaccharides called agarobiose composed of galactose and 3,6- anhydrogalactose residues (Figure 9.9). Agarose is a neutral, high molecular weight (120kDa) linear polymer of alternating (1–4)-linked 3,6 anhydro-α-L-galactopyranose and (1–3)-linked β-D-galactose residues (Rodríguez et al., 2009), as shown in Figure 9.10. Due to this property, its concentration in agar affects the strength of the gel. Agar with a high concentration of agarose and less sulphate (0.5%) makes a stronger gel. Generally, a typical agar is composed of 70% agarose, and the rest is a branched agaropectin chain. Agaropectin contains calcium, magnesium, potassium, and sodium sulfate esters at the 6th position of the β-(1,4)-galactose or in the 4th and 6th positions of a-(1,3)-galactose unit. Additionally, methyl groups, pyruvate, β-d-xylopyranose, and 4-o-Me-a-l-galactopyranose residues can occur in its structure, as shown in Figure 9.11. Since agaropectin contains more anionic groups (5–8%) and high molecular weight (12.6kDa), it constitutes the non-gelling portion of agar. Agar gel formation can occur at a low concentration of 0.2% of agar at 80°C, followed by cooling at 40°C (Lahaye and Rochas, 1991; Asadova et al., 2020).
Spray-freeze-dried Particles as Novel Delivery Systems for Vaccines and Active Pharmaceutical Ingredients
Published in S. Padma Ishwarya, Spray-Freeze-Drying of Foods and Bioproducts, 2022
The particle penetration property was tested by injecting the insulin-loaded drug particles into tissue mimicking 3% agar hydrogel phantoms using an 8 mm inline venturi device (Fig. 8.14) loaded with a 60 bar helium cylinder. Agar is a polysaccharide extracted from red algae, which contains about 70% agarose and 30% agaropectin. It mimics the mechanical material properties of human skin. Upon injecting the pure TMDD particles (0% theoretical insulin load), neither particles nor particle fragments were observed in the sliced agar targets, when visualized under the microscope. This is because the particles dissolved instantaneously due to the high aqueous content of agar hydrogel (97%). Fig. 8.15 shows the microscopic image of polydisperse insulin particles injected into agar hydrogel test beds. After injection, the particles depicted an elongated, disrupted and slightly porous appearance. Particulate clusters of very small particles were retained in the agar. The highly soluble TMDD matrix seemed to dissolve instantly, leaving behind the clusters of originally suspended small and poorly soluble insulin nanoparticles (Schiffter et al., 2010).
Recent Advances in the Production of Multilayer Biodegradable Films
Published in Sanjay Mavinkere Rangappa, Parameswaranpillai Jyotishkumar, Senthil Muthu Kumar Thiagamani, Senthilkumar Krishnasamy, Suchart Siengchin, Food Packaging, 2020
Daiane Nogueira, Gabriel da Silva Filipini, Vilásia Guimarães Martins
Different strategies have already been suggested to overcome these weaknesses, including the development of polysaccharide bilayers. Thus, agar, a polysaccharide extracted from marine red algae of the Rhodophyceae class (Malagurski et al., 2017), which is biocompatible, has high mechanical resistance and good film-forming properties, making it a good alternative. Agar is composed of agarose and agaropectin molecules. Agarose is a neutral and linear molecule of 3,6-anhydro-L-galactose units linked to β-1,3-linked-D-galactose and α-1,4 and mediates the gelation of agar hydrogels, while agaropectin is a charged, sulfated, branched and non-gelling unit (Garrido et al., 2016; Malagurski et al., 2017). The relative insolubility and the ability of this polysaccharide to produce strong gels may help to reduce the water vapor permeability of the agar films (Vejdan et al., 2016).
Triaxial test behaviour of silty sands treated with agar biopolymer
Published in International Journal of Geotechnical Engineering, 2021
S. Smitha, K. Rangaswamy, D. S. Keerthi
Agar biopolymer was chosen for the present study due to its ability to form three dimensional gel networks within the soil mass. Also, it exhibits a unique property of gelation hysteresis since there is a considerable difference between its gelling and melting temperature. Agar forms a solution in water at a temperature of around 90°C; as the temperature of the solution reduces its viscosity starts increasing, and when the temperature reaches about 30°C, it would form a firm hydrogel. Due to this property agar has found use in various applications like pharmaceuticals, food industry, microbiology etc. Chemically, agar biopolymer is composed of agarose and agaropectin; agarose is responsible for the gelling nature of agar (Armisen and Galatas 1987). It is commonly obtained from certain species of red algae like gracillaria, gellidium etc. Food grade agar that was available in a dry powder form was used, which was procured from the manufacturer, Urban platter. Its source as specified by the manufacturer is Gracilaria cornopifolia, and its gel strength is 700 g/cm2.
Green in the deep blue: deep eutectic solvents as versatile systems for the processing of marine biomass
Published in Green Chemistry Letters and Reviews, 2022
Colin McReynolds, Amandine Adrien, Natalia Castejon, Susana C. M. Fernandes
Agar is a commercially important product extracted from red seaweeds. It is a mixture of polysaccharides: linear agarose (about 70%, repeating unit – agarobiose) and agaropectin (D-galactose and L-galactose with acidic side-groups). With these types of polymers, DESs have largely been used as plasticizers or material adjuvants.