"Polysaccharides" or "Hydrocolloid Gums" are produced by microbes used as delicious food additives such as ice creams, frozen desserts, bakery and yogurt preparation and salad dressings. It is also used as water behavior modifier, thickener, gelling agent, emulsifier, suspending agent and stabilizer.
Microbial polysaccharides can be either homo (starch and cellulose) or hetropolysaccharides (xanthan and dextran). Generally, microbial polysaccharides are of three types which are:
(1) The cell wall polysaccharides,
(2) The intercellular polysaccharides and
(3) The exocellular polysaccharides.
The cell wall and intercellular polysaccharides (capsular polysaccharides) are produced capsular products which used to have difficulty during their recovery to separate out from cell biomass. Yeast glucan, starch and fungal chitin are typical examples of capsular polysaccharides. The exocellular polysaccharides (non-capsular polysaccharides) are constantly diffuse into the production medium which makes the cell culture slimy and viscous. Hence, these types of polysaccharides are free from protein and cell debris as well as easy to extract from production medium during their harvesting. Xanthan, dextran, levan, curdlan, welan and gellan are typical exocellular polysaccharides.
Anaerobic microbes have characteristic metabolic features of biosynthesis of polysaccharide. In commercial production of microbial polysaccharides, fermentation strategy is adjusted for production of higher yield of polysaccharide rather than cellular biomass production by supplying sugar components as the major carbon source. For enlargement of polysaccharides polymers is termed as "Extrusion Mechanism" which lead to protruding of side chains of the polymer out of the cell surface at certain extrusion sites. Thus, elongation of the polymer chain occurs by a "Screwing Mechanism" in which the repeat unit of the polymer generated inside the cell is linked at the non-reducing end at specific extrusion site to give fibrillar structure of many microbial polysaccharides. Inter-twisting of these linear-branched polysaccharides polymers can give rise to the known double or triple helix configuration such as xanthan and gellan which, in turn, can be result in rigid rod like structure to provide high viscosity of these microbial produced polysaccharides as gelling agent.
About Author / Additional Info:
Author name and address:
Dr. Kirti Rani Sharma,
Assistant Professor (II),
Amity Institute of Biotechnology,
Amity University Uttar Pradesh, Noida
Sec-125, Gautam Buddha Nagar, Noida-201303 (UP), India.
Email ID: email@example.com, Kirtisharma2k@rediffmail.com