Biomolecules from Natural Sources. Группа авторов. Читать онлайн. Newlib. NEWLIB.NET

Автор: Группа авторов
Издательство: John Wiley & Sons Limited
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Жанр произведения: Техническая литература
Год издания: 0
isbn: 9781119769613
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The gums are naturally occurring substances, mainly carbohydrate in nature and are being used since the beginning of civilization for various purposes e.g., a food ingredient (for humans and cattle) and manufacturing domestic items. The properties of natural gums have been known for a long time including its gelling, thickening and binding properties. The mannans are commonly referred to as “gums”. Guar gum comes from the endosperm of the seed of the legume plant Cyamopsistetragonolobus. The gum is commercially extracted from the seeds essentially by a mechanical process of roasting, differential attrition, sieving and polishing [202]. Khaya gum is a polysaccharide obtained from the incised trunk of the tree Khaya grandifoliola from the family Meliaceae. Acacia gum (GA) is the exudate from the Acacia senegal and Acacia seyal trees, belonging to Leguminosae family [203]. Most of the GA is harvested from the arid lands of Sudan, Chad, Nigeria, Senegal, and Ethiopia. Sudan is the largest exporter, accounting for up to 80% of the trade, followed by Nigeria. The use of GA dates back to 5000 years ago. GA has also found use in the textile industry for its ability to enhance tensile strength of the yarns [204]. Glactomannan is one of the principle biotechnologically interesting molecules. There is a particular interest in the synergistic interactions between both galactomnnans and glucomannans with xanthan, carrageenans and agarose. Glucomannan is used as antioxidant [205].

      2.4.12 Hyaluronic Acid

      2.4.13 Fructans

      Inulin and levan fructans (which used to be called fructosans, and are described as “inulin” in commercial practice) are found in large amounts in only a few plants but are widely distributed [211].

      2.4.14 Marine Polysaccharides

      Seaweed contains different types of polysaccharides such as alginates, carrageenans, agar (and its agarose constitutent) shells, crabs, and lobsters. Shrimps contain chitin and its soluble derivative,

      chitosan.

      2.4.14.1 Alginate

      The naturally occurring alginate polymers have great potential in drug formulation because of their extensive application as food additives and their recognized lack of toxicity. Alginate is a historic term used in many applications such as the cosmetic and pharmaceutical industries. As this group of polymers possess numerous characteristics that makes it useful as a formulation aid, both as a conventional excipient and more specifically as a tool in polymeric-controlled drug delivery. The alginates were discovered by a British Pharmacist, E.C.C. Stanford; commercial production started in 1929. The annual production of alginates in the world is about 30 000 tonnes. Alginic acid and it’s salts (Ca, Mg, Na and K) are abundantly present in brown algae (pheophyta) of the genera macrocystis, laminaria, ascophyllum, alario, ecklonia, eisenia, nercocystis, sargassum, cystoseira, and fucus. Acetylated alginates are also isolated from some bacteria genera pseudomonas and acetobacter. Red algae belonging to the family coralenacease also contain these substances. Alginate are used in nanoparticles, grafted donor sites in burns, wound dressing and in recycling of textile dye [212].

      2.4.14.2 Carrageenans and Red Seaweed

      2.4.14.3 Agar and Agarose

      A polysaccharide produced commercially from red algae blonging to the family Rhodophyceae particullay from Gelidium and Gracilaria. Agar polysaccharide is composed of neutral polysaccharide (agarose), charged polysaccharide (agaropectin), and highly sulfated galactans. It is used as a food additive in icings, glazes, processed cheese, jelly, sweets and marshmallows. Agar is used for growing microorganisms while most species are unable to degrade it. Agar is resistant to high temperature, can form brittle gels and can hold a large number of soluble solids. It used as gelling, thickening, stabilizing and viscosity controlling agent for jellies, candies and jams.

      It shows also many medical, pharmaceutical and industrial applications such as a laxative, an anti-rheumatic agent and for making dental impressions. Agarose is a neutral polysaccharide in agar and is used mainly in the separation of biological macromolecules. Also, it has antioxidative, antibacterial, antimutagenic and immune modulating activities.

      2.5 Biopolymer Type Number 4: Organic Polyoxoesters

      [37, 214]. PHA was proved to be biocompatible and can be used in tissue engineering, implantations, and so on. Retinal pigment epithelium cells grow well on P(3HB-co-3HV) as a monolayer for their subretinal transplantation. PHA can be melted or solution processed into a variety of forms. Salt leaching, dip coating and thermally induced phase separation were used to produce scaffolds for cardiovascular tissue engineering. When seeded with cells and cultured in vitro, these scaffolds were used to create living tissue implants [215].