Other modified dextrans such as Sephadex are used extensively in the separation of biological compounds. In the industrial area, dextrans are being incorporated into x-ray and other photographic emulsions. Dextran is used as a food-grade biopolymer, nanoparticles, hydrogel, and in transdermal delivery [180].
Dextran-hemoglobin compounds may be used as blood substitutes that have oxygen delivery potential and can also function as plasma expanders.
2.4.7 Pullulan
Pullulan is a non-toxic exopolysaccharide of fungi origin. It is non-toxic, non-immunogenic, non-mutagenic and non-carcinogenic [181]. It produced from Aureobasiduim pullulans [182]. Pullulan is biodegradable impermeable to oxygen, non-hygroscopic and non-reducing. Pullulan possesses oxygen barrier properties, good moisture retention and it inhibits fungal growth so it enhances the shelf-life. It is used in tissue engineering, molecular chaperones, plasma expender and surface modification. Pullulan is a linear polymer made of monomers that contain three glucose sugars linked together. For more than a decade, a Japanese firm, Hayashibara Biochemical Laboratories, has used a simple fermentation process to produce pullulan. Some feedstocks are used for this process, including the streams containing simple sugars. Pullulan can be chemically modified to produce a polymer that is either less soluble or insoluble in water. The thermal and ionic (electrical) properties of pullulans can also be altered.
It can be used as a food additive, providing bulk and texture. It is tasteless, odorless, and non-toxic. It does not break down in the presence of naturally occurring digestive enzymes and therefore has no caloric content. So, it can be used as a food additive in low-calorie foods and drinks, in place of starch or other fillers. In addition, pullulan inhibits fungal growth and has good moisture retention, and thus can be used as a preservative. Pullulan can also be used as a water-soluble, edible film for the packaging of food products. It is transparent, impermeable to oxygen, and oil- and grease-resistant. Foods can be either immersed in a solution of pullulan or coated by a polymer spray. After the pullulan coating is dried, an airtight membrane is formed. Pullulan is used as gold nanoparticles for cancer treatment, drug delivery and in controlled release of biopharmaceutical [183, 184].
2.4.8 Glucan
A common source for glucan is baker’s yeast, Saccharomyces cerevisiae, although it is also found in some other sources (bacteria, fungi, lichen, and higher plants, such as, barley). Large supplies of inexpensive yeast are available from both the baking and the brewing (brewer’s yeast) industries. Glucans are the most abundant polymers in yeast, making up approximately 12–14% of the total dry cell weight. Glucan is readily purified from yeast cells by using hot alkali treatment to remove all other cellular materials, thereby allowing recovery of the insoluble glucan material. Yeast glucan particles purified by this method contain both HMW and lower molecular weight polymers. Glucan is used as an immunosuppressive [185]. Glucan has been modified and applied in different applications such as hydrogels [32, 186], and a potential prebiotic [187], in supporting the treatment of viruses [188] and many others. Although glucans are being exploited mainly for their antitumor, anti-infectious, and radioprotective properties, they also have non-medical applications. Glucans resist breakdown when attacked by digestive enzymes, and thus can be used as non-caloric food thickeners. Other possible applications include use in sustained-release tablets, encapsulation of oxygen for mass transfer in fermentation reactions, and as a solid support material for chromatographic separations [189–193].
2.4.9 Gellan
Gellan is a complex polysaccharide having a four-sugar repeat unit (glucose–glucuronic acid–glucose–rhamnose). It is produced by the bacterium Pseudomonas elodea, which is derived from plant tissue. The properties of gellan can be easily modified. A hot caustic treatment of gellan yields a polymer that has the desirable characteristic of low viscosity at high temperature. Cooling gellan in various cations (such as, calcium) results in forming strong gels. Gellan is used to inhibit Plasmodium falciparum growth in the food industry, personal care products [194], pharmacy and medicine [194], hard capsule [195], drug delivery [196], microspheres [197], cell differentiation [198], microbeads [199], nanocomposites [200] and many others.
2.4.10 Pectin
Pectin is a water-soluble colloidal carbohydrate that occurs in ripe fruit and vegetables. Pectin is a family of complex polysaccharides present in the walls that surround growing and dividing plant cells. It is also present in the junctional zone between cells within secondary cell walls including xylem and fiber cells in woody tissue. Its traditional application is in making fruit jellies and jams. Pectin is an essential component in the initial growth and ripening process of fruit and is often a waste material from the food and fruit processing industry. Pectins are made either from apple pulp, byproducts of cider manufacture, or from the peel of citrus fruits such as limes, the preferred source, lemons or oranges, byproducts of fruit juice manufacture. Pectins have long been recognized as the main gel-forming agents in jams and fruit-based preserves. It was known for a time that polysaccharides can stabilize colloidal sols and suspensions. The simple addition of water-soluble pectate for example: usually the sodium salt will prevent aggregation and precipitation. Gels can be obtained by mixing gelatin and pectin into lipid in water emulsions. The results are low-fat margarines and other spread type products. Pectins are used in drug delivery and as a colloidal [201].
2.4.11 Gums
Gums are plant substances which can be dissolved or dispersed in water to form more or less viscous colloidal solutions or dispersions. 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
Hyaluronic acid capsular component by the bacteria, Staphylococcus and some Streptococci. Hyaluronic is used in drug delivery, as an antioxidant, as a cationic biopolymer, and in nanotube technology [40, 206–210].
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.
