Functionality of exopolysaccharides produced by lactic acid bacteria”

RUAS MADIEDO PATRICIA; ABRAHAM ANALIA G; MOZZI FERNANDA; GONZALEZ DE LOS REYES GAVILAN CLARA

in Molecular Aspects of Lactic Acid Bacteria for Traditional and New Applications

Research Singpost

Lugar: Kerala, India ; Año: 2008; p. 137 - 166

Many strains of lactic acid bacteria (LAB) are able to produce exopolysaccharides (EPS). Depending on their chemical composition, EPS can be classified as homopolysaccharides (HoPS), which contain a single type of monosaccharide, and heteropolysaccharides(HePS), which are formed of several repeating units of different monosaccharides.Most HoPS are synthesized by extracellular glycansucrases that use sucrose asthe glycosyl (fructose or glucose) donor. In the HePS the precursor repeatingunitsare formed intracellularly and assembled extracellularly. The differentgenes participating in the production of HePS, and the regulation of the chainlength, are usually organized in clusters. HoPS are generally longer in sizeand are produced in higher amounts than HePS.This chapter reviews the current knowledge about the physiological role ofEPS in the producing LAB strains, as well as their possible benefits for humanhealth and their technological application to the manufacture of dairyproducts.The physiological functions of EPS in the producing bacteria have not yetbeen clearly determined although they might be related to better adaptation to,and recognition of, the environment. It has been suggested that EPS producedby LAB act as protective agents against desiccation, bacteriophage attack,antimicrobial compounds, and phagocytosis. They can also be involved in theadhesion to surfaces such as the human intestinal mucosa. EPS may exertbeneficial effects on human health, although more in vivo studies are needed todemonstrate their efficacy. Among these beneficial effects, their possible roleas prebiotics, serum lowering cholesterol ability, and immunomodulatory andanticarcinogenic activities have been suggested. Some LAB strains whichproduce EPS are being used in the industry because they confer beneficialphysical properties to dairy products, such as the improvement of rheologicalproperties and reduction of syneresis in yoghurts, and better consistency ofcurd in low-fat ripened cheeses. In spite of these interesting technologicalproperties, the use of EPS from LAB as food additives in the industry is stilllimited because of the low production levels compared to the xanthansproduced by Gram-negative microorganisms.