Abstract
The production of exopolysaccharides (EPS) by lactic acid bacteria (LAB) has attracted particular interest in the food industry. EPS can be considered as natural biothickeners as they are produced in situ by LAB and improve the rheological properties of fermented foods. Moreover, much research has been conducted on the beneficial effects of EPS produced by LAB on modulating the gut microbiome and promoting health. The EPS, which varies widely in composition and structure, may have diverse health effects, such as glycemic control, calcium and magnesium absorption, cholesterol-lowering, anticarcinogenic, immunomodulatory, and antioxidant effects. In this article, the latest advances on structure, biosynthesis, and physicochemical properties of LAB-derived EPS are described in detail. This is followed by a summary of up-to-date methods used to detect, characterize and elucidate the structure of EPS produced by LAB. In addition, current strategies on the use of LAB-produced EPS in food products have been discussed, focusing on beneficial applications in dairy products, gluten-free bakery products, and low-fat meat products, as they positively influence the consistency, stability, and quality of the final product. Highlighting is also placed on reports of health-promoting effects, with particular emphasis on prebiotic, immunomodulatory, antioxidant, cholesterol-lowering, anti-biofilm, antimicrobial, anticancer, and drug-delivery activities.
Highlights
It is well-known that lactic acid bacteria (LAB) can synthesize a variety of polysaccharides
(1→6)-linked Glc, (1→3)-linked Gal, (1→4)-linked Gal, (1→4)-linked Glc, and (1→2, 6)linked Gal [65]. Because of these types of linkages, kefiran cannot be hydrolyzed by the digestive enzymes of the human gastrointestinal tract, but it can be fermented by colon bacteria [64]
Despite the large number of researchers working on EPS-producing LAB, there is still insufficient information on the kinetics of EPS synthesis, where variations in production yield and EPS composition can lead to complete loss of production, as numerous variables can affect production and structure [95,109]
Summary
It is well-known that lactic acid bacteria (LAB) can synthesize a variety of polysaccharides. HePS (Table 2), unlike HoPS, have a more complex structure as they are composed of several repeating units of sugars, such as pentose (D-ribose, D-arabinose, D-xylose), hexose (D-glucose, D-galactose, D-mannose), N-acetylated monosaccharides (N-acetylglucosamine and N-acetyl-galactosamine), or uronic acids (D-glucuronic acid, D-galacturonic acid), and may be branched or unbranched [8,60,61] They are produced by members of the genera Lactobacillus, Lactococcus, and Streptococcus [10]. Kefiran is a water-soluble branched glucogalactan with a complex structure consisting of D-glucose (Glc) and D-galactose (Gal) in approximately equal amounts, with (1→6)-linked Glc, (1→3)-linked Gal, (1→4)-linked Gal, (1→4)-linked Glc, and (1→2, 6)linked Gal [65] Because of these types of linkages, kefiran cannot be hydrolyzed by the digestive enzymes of the human gastrointestinal tract, but it can be fermented by colon bacteria [64].
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