Table 1 Commercially important microbial polymers: the most relevant properties and applicationsa
From: Production of biodegradable microbial polymers from whey
Polymer class | Producer | Monomers | Characteristics of primary structure | Properties | Applications |
|---|---|---|---|---|---|
Xanthan | Xanthomonas spp., mainly X. campestris | Glucose, mannose and glucuronate | β-(1,4)-linked repeating extracellular heteropolymer consisting of pentasaccharide units | Hydrocolloid —High viscosity yield at low shear rates even at low concentrations; —Stability over wide temperature, pH and salt concentrations ranges | Foods, petroleum, industry pharmaceuticals, cosmetics and personal care products, agriculture |
Alginate | Pseudomonas spp. and Azotobacter spp. | Mannuronic acid and guluronic acid | β-(1,4)-linked non-repeating non-repeating extracellular heteropolymer | Hydrocolloid Gelling capacity Film-forming | Food hydrocolloid Medicine Surgical dressings Wound management Controlled drug release |
Gellan | Sphingomonas spp. | Glucose, rhamnose and glucuronate | β-(1,3)-linked repeating extracellular heteropolymer consisting of tetrasaccharide units | Hydrocolloid -Stability over wide pH range Gelling capacity Thermoreversible gels | Foods Pet food Pharmaceuticals Research: agar substitute and gel electrophoresis |
Curdlan | Agrobacterium spp., Rhizobium spp. and Cellulomonas spp. | Glucose | β-(1,3)-linked extracellular homopolymer | Gel-forming ability Water insolubility Edible and non-toxic Biological activity | Foods Pharmaceutical industry Heavy metal removal Concrete additive |
Dextran | Leuconostoc spp. and Streptococcus spp. | Glucose | α-(1,2)/α-(1,3)/ α-(1,4)-branched α-(1,6)-linked extracellular homopolymer | Non-ionic Good stability Newtonian fluid behaviour | Foods Pharmaceutical industry: Blood volume expander Chromatographic media |
Levan | Bacillus spp.,Erwinia spp., Halomonas spp,Zymomonas mobilis | Fructose | β-(2,6)-linked, β-(2,1)-branched extracellular homopolymer | Low viscosity, high water solubility, Anti-tumour activity Anti-inflammatory. Adhesive strength, Film-forming capacity | Food (prebiotic), Feed, Medicines, Cosmetics Industry |
Pullulan | Aurebasidium pullulans Cytaria spp. | Glucose | α-(1,6)-linked maltotriose (α-(1,4)-linked glucose) units extracellular homopolymer | Easily water soluble, high adhesion, sticking, lubrication, and film forming abilities, biocompatible | Food packaging edible coatings (food, pharmacy tablets), Cosmetics, Paper coating, Flocculating agent |
Cellulose | Gluconacetobacter spp. (mainly G. xylinus), Komagataeibacter spp., Agrobacterium spp., Alcaligenes spp., Rhizobium spp., Sarcina spp., Azotobacter spp. | Glucose | β-(1,4)-linked extracellular homopolymer | High crystallinity Insolubility in most solvents High tensile strength Moldability | Foods (indigestible fibre) Biomedical Wound healing Tissue engineered blood vessels Audio transducers diaphragm |
Polyhydroxyalkanoates (PHA) (polyesters) | Azotobacter spp., Alcaligenes spp., Cupraividus spp., Haloferax spp., Pseudomonas spp.; | (R)-3-hydroxy fatty acids | Intracellular heteropolymer | Thermoplastic or elastomeric materials, with melting points ranging from 40 to 180 °C, resistance to moisture, aroma barrier, UV stable, soluble in halogenated solvents | Biodegradable plastics Drug delivery Tissue engineering Food packaging biomaterial and matrices for displaying or binding proteins |