Fermentation for Polysaccharides

As a leading CDMO in fermentation, BOC Sciences provides one-stop services to manufacture microbial fermented products such as polysaccharides. Our polysaccharides platform is dedicated to meet the needs of customers in various industries. Our scientists support the development of new strains or fermentation processes to biosynthesize the desired natural products and to scale up production.

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Introduction of Polysaccharides

Polysaccharides are the major components of carbohydrates in nature and are made up of monosaccharides linked by glycosidic bonds. Polysaccharides can be distinguished by their monosaccharide composition, chain length and number of branched chains. Polysaccharides can be divided into: homogeneous polysaccharides and heterogeneous polysaccharides, which denote polysaccharides composed of only one monosaccharide molecule and polysaccharides containing more than one monosaccharide, respectively. Three important polysaccharides, namely starch, glycogen and cellulose, all consist of glucose and are homogeneous polysaccharides.

Polysaccharides can be synthesized by different efficient methods and can also be isolated from plants, algae, and microorganisms. The ability to produce polysaccharides with diverse biological functions is widespread in microorganisms. Bacteria can synthesize cytoplasmic storage polysaccharides (e.g. glycogen, bacterial starch) and cell surface-associated polysaccharides (peptidoglycan, lipopolysaccharides, lipooligosaccharides, teichoic acids, lipoteichoic acids, and other cell wall polysaccharides. Polysaccharides are produced through complex metabolic processes in microbial cells and accumulated in the cytoplasm, such as polyphosphates, polyhydroxyalkanoates, starch, cyanophycin, and glycogen.

Fermentation Production of Polysaccharides

The synthesis pathway of microbial extracellular polysaccharides (EPS) consists of three main steps: substrate digestion, major metabolite pathway and polysaccharide synthesis. Substrates may be catabolized by intracellular phosphorylation or by direct periplasm oxidation. The production of polysaccharides requires the biosynthesis of effective precursors, which are energy-rich monosaccharides that can be produced from phosphorylated sugars, mainly nucleoside diphosphate sugars (NDP-sugars).

Several examples of polysaccharide produced by microorganisms

The microorganisms can produce large amounts of polysaccharides in the presence of surplus carbon source in the growth medium while limiting nitrogen supply. In the upstream process of fermentation production, the need for extracellular polysaccharide-producing microorganisms is the development of new strains with increased yield or improved functional properties. Strain improvement can be done using genetic and metabolic engineering methods, such as the use of recombinant DNA technology to improve the performance of the host cells. In the downstream process of fermentation, polysaccharide production is mostly carried out by batch culture fermentation. As the polysaccharide production increases, the viscosity of the culture broth increases significantly. Polysaccharides can be precipitated with salts, acids or organic solvents and isolated and purified by appropriate techniques.

Fig. 1 Extracellular polysaccharides screening (Zeidan, 2017)

Application of Polysaccharides

Due to their high efficiency, economy, non-toxicity, biocompatibility and biodegradability, polysaccharides are widely used in different applications, including food, drug delivery, tissue engineering, wound dressing, and bioremediation fields. Polysaccharides have been widely used in medical applications, many of which have antitumor, antibacterial, immunomodulatory, and hypoglycemic properties. For example, the glycan portion of many vaccines binds to carrier proteins, resulting in highly effective and safe vaccines. In addition, polysaccharides are widely used in the food and dairy industries. For example, pullulan is a water-soluble polysaccharide formed by many yeast species, and they can be used as texture enhancers in foods. Under biologically active conditions, pullulan compounds are biodegradable polymers and are heat resistant.

Reference

1. Zeidan, A. A., et al., Polysaccharide production by lactic acid bacteria: from genes to industrial applications, FEMS Microbiology Reviews, 2017, 41, S168-S200.