**7. Lactic acid bacteria as source of exopolysaccharides**

### **7.1. Definition and classification of exopolysaccharides**

A number of LAB can produce a variety of long chain sugar polymers, called exopolysaccharides (EPS) which are mainly employed for the production of fermented dairy products. They are synthesized either extracellularly from sucrose by glycansucrases or intracellularly by glycosyltransferases from sugar nucleotide precursors [148]. These EPS can be classified according to their chemical composition and biosynthesis mechanism as homopolysaccharides, consisting of a single type of monosaccharide and heteropolysaccharides consisting of repeating units of two or more types of monosaccharides, substituted monosaccharides and other units like phosphate, acetyl and glycerol [149-151].

Homopolysaccharides are further divided into fructans including levan and inuline-type and glucans including dextran, mutan, alteran and b-1, 3 glucan [152]. On the other hand, heteropolysaccharides demonstrate little structural similarity to one another. Their production is influenced by the bacterial growth, phase, medium composition (carbon and nitrogen source), pH and temperature [153]. They can be produced by *Lactococcus spp*. and *Lactobacillus spp*. and they play a crucial role in the food industry [151]. Homopolysaccharides can be introduced in sourdough products, influencing the structural quality and backing ability in bakery products, while heteropolysaccharides are used as food additives in dairy products [154]. EPS contribute to the organoleptic quality of the fermented foods, in texture, taste perception, mouth-feel and stability [153,155]. The above researchers reported that there is no information about the effects of bacterial EPS in nondairy foods, such as meat products, sauerkraut and vinegar. Although EPS are tasteless, they prolong the time that the milk product spends in the mouth, enhancing its delicacy through an improved volatilization of the intrinsic flavors [153,155].

## **7.2. Applications of exopolysaccharides in the industry**

602 Lactic Acid Bacteria – R & D for Food, Health and Livestock Purposes

[147].

glycerol [149-151].

**6. Lactic acid bacteria as source of enzymes** 

modifications improve the taste and flavor of wine [144].

**7. Lactic acid bacteria as source of exopolysaccharides** 

**7.1. Definition and classification of exopolysaccharides** 

LAB possess an extensive collection of enzymes many of which have the potential to influence the composition and the processing, organoleptic properties and quality of foods and feeds. LAB release various enzymes into the gastrointestinal tract and exert potential synergistic effects on digestion and alleviate symptoms of intestinal malabsorption [141]. In other cases these organisms may serve as a source for the preparation of enzyme extracts that are able to function under the environmental conditions of fermentation [142]. The enzymatic activity has been studied mainly in LAB isolated from wine or other fermented foods like cheeses and yoghurt [143,144]. Species of *Lactococcus* and *Pediococcus* are the LAB most commonly associated with fermented foods [143]. The LAB produced enzymes and in particular amylases which are the most stable can be used in sourdough technology for the natural improvement of bread texture [145]. Moreover, LAB contribute to the aroma and flavor of fermented foods. Certain peptidases produced by *Lactococcus lactis subsp. cremoris* improved the sensory quality of cheese [146]. In addition, proteolysis and lipolysis may enhance the flavour of most varieties of cheese [147]. LAB strains isolated from a traditional Spanish Genestoso cheese were evaluated for the enzymatic activity and it was reported that dipeptidase activity of high level was found for *Lactococcus spp*, enterolytic activity was detected for *Enterococcus spp*., while carboxypeptidase activity was very low or undetectable

Also, enzymes play an important role in winemaking. Wine flavor and aroma apart from aromas originating in grapes and alcoholic fermentation, is derived mainly from the activity of the LAB, through the action of their enzymes. These bacteria grow in wine during malolactic fermentation, following alcoholic fermentation, while a broad range of secondary

A number of LAB can produce a variety of long chain sugar polymers, called exopolysaccharides (EPS) which are mainly employed for the production of fermented dairy products. They are synthesized either extracellularly from sucrose by glycansucrases or intracellularly by glycosyltransferases from sugar nucleotide precursors [148]. These EPS can be classified according to their chemical composition and biosynthesis mechanism as homopolysaccharides, consisting of a single type of monosaccharide and heteropolysaccharides consisting of repeating units of two or more types of monosaccharides, substituted monosaccharides and other units like phosphate, acetyl and

Homopolysaccharides are further divided into fructans including levan and inuline-type and glucans including dextran, mutan, alteran and b-1, 3 glucan [152]. On the other hand, heteropolysaccharides demonstrate little structural similarity to one another. Their production is influenced by the bacterial growth, phase, medium composition (carbon and In the last years, EPS derived from LAB have received increasing interest because of their GRAS status and their properties. EPS can improve the rheology of fermented foods (viscosity and elasticity) as natural biothickeners, emulsifiers, gelling agents and physical stabilizers to bind water and limit syneresis [153,156]. In particular commercial products like LAB dextran could be utilized apart from foods in gel filtration products, in the pharmaceutical industry, as blood volume expander and flow improver, in chemistry as paper and metal plating processes, in enhanced oil recovery and in chromographic media. Furthermore, levan can find use in the food industry as biothickener, while alteran as low-viscocity factor, extender, etc [128,151,157]. Additionally, EPS may produce oligosaccharides having prebiotic properties that could find important applications in functional foods [158]. The successful application of EPS in the manufacture of fermented milks is determined by the ability to bind water, interact with proteins and increase the viscosity of the milk serum phase [159]. Although, many LAB strains are able to produce EPS, their yield is low [149] and their industrial applications for the improvement of the properties of food products are limited [155].

## **7.3. Potential health benefits of exopolysaccharides**

Apart from the technological benefits some EPS derived from LAB are claimed to have beneficial physiological effects on consumer's health. These benefits are detectable at very low concentrations [153]. The EPS due to their increased viscosity in foods may remain for longer time in the gastrointestinal tract and therefore be beneficial to the transient colonization by probiotic bacteria [153,160]. Another health benefit is the generation of short chain fatty acids by colonic microflora degradation in the gut. Several of these fatty acids are possibly involved in the prevention of colon cancer [153,159]. In addition, LAB synthesized EPS appear to have anti-tumor, anti-ulcer, immuno-modulating and cholesterol-lowering activity [155].

### **7.4. Factors limiting the use of exopolysaccharides**

The EPS used in the industry represent only a small fraction of the biopolymers used. The reasons are their economical production which needs a global knowledge of their

biosynthesis and an adapted bioprocess technology [151]. Moreover, large scale production of LAB derived EPS is low, since LAB being anaerobes, are relatively inefficient in converting energy from carbohydrates, compared to aerobes [149,161]. So this technological barrier must be overcome for cost effective production of EPS. Furthermore, the genetic instability of EPS production is a problem to industrial applications, resulting in loss or reduction of production or change in the composition of EPS [162].

Lactic Acid Bacteria as Source of Functional Ingredients 605

**Author details** 

*Thessaloniki, Greece*  Eleftherios Bonos

**10. References** 

Portland, USA.

health. 29: 4-8.

Panagiota Florou-Paneri and Efterpi Christaki

Review. Pharmacol. res. 63: 366-376.

Taxonomy. Int. j. food Microb. 36: 1–29.

(Vol. 3). EOLSS Publishers Co Ltd, UK.

Publishing, Iowa, USA. p. 24.

*Animal Production, Faculty of Technology of Agronomics,* 

*Technological Educational Institute of Western Macedonia, Florina, Greece* 

*Laboratory of Nutrition, Faculty of Veterinary Medicine, Aristotle University of Thessaloniki,* 

[1] Aureli P, Capurso L, Castellazzi AM, Clerici M, Giovannini M, Morelli L, Poli A, Pregliasco F, Salvini F, Zuccotti (2011) Probiotics And Health: An Evidence-based

[2] Barinov A, Bolotin A, Langella P, Maguin E, Van De Guchte M (2011) Genomics Of The Genus *Lactobacillus*. In: Sonomoto K, Yokota A, editors. Lactic Acid Bacteria and Bifidobacteria: Current Progress in Advanced Research. Caister Academic Press,

[3] Stiles ME, Holzapfel WH (1997) Lactic Acid Bacteria Of Foods And Their Current

[7] Hutkins RW (2006) Microbiology and Technology of Fermented Foods. Blackwell

[8] Teitelbaum JE, Walker WA (2002) Nutritional Impact Of Pre- and Probiotics As

[9] Korhonen J (2010) Antibiotic Resistance Of Lactic Acid Bacteria. Dissertations in

[10] Hamdan AM, Sonomoto K (2011) Production Of Optically Pure Lactic Acid For Bioplastics. In: Sonomoto K, Yokota A, editors. Lactic Acid Bacteria and Bifidobacteria: Current Progress in Advanced Research. Caister Academic Press, Portland, USA. [11] Parker RB (1974) Probiotics, The Other Half Of The Antibiotic Story. Animal nutr.

[13] FAO/WHO – Food and Agriculture Organization / World Health Organization (2001) Health And Nutritional Properties Of Probiotics In Food Including Powder Milk With Live Lactic Acid Bacteria, Report Of A Joint FAO/WHO Expert Consultation On Evaluation Of Health And Nutritional Properties Of Probiotics In Food Including Powder Milk With Live Lactic Acid Bacteria, Cordoba. Argentina. http://www.who.int/ foodsafety/ publications/ fs\_management/ en/ probiotics.pdf. Accessed 2011 Dec 15.

[4] Johnson-Green P (2002) Introduction To Food Biotechnology. CRC Press, Boca Raton. [5] Halasz A (2009) Lactic Acid Bacteria. In: Lasztity R, editor. Food Quality and Standards

[6] Jay J (2000) Modern Food Microbiology (6th edition). Aspen, Maryland

Protective Gastrointestinal Organisms. Annu. rev. nutr. 22: 107-138.

[12] Fuller R (1989) Probiotics In Man And Animals. J. appl. bact. 66: 365-378.

Forestry and Natural Sciences, University of Eastern Finland.

Increasing the knowledge on EPS structure may lead to the production of the "designer" EPS, including the modification primary in structure by altering their physical properties, their function and their production levels. However, for such production of EPS legal approval and the acceptance by the consumers and the food industries are required [151,163]. However, if these biomolecules are to be developed commercially, they must be cost effective.
