Extracellular polysaccharides produced by bacteria of the Leuconostoc genus
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(2020) 36:161
REVIEW
Extracellular polysaccharides produced by bacteria of the Leuconostoc genus Peteris Zikmanis1 · Karlis Brants2 · Sergejs Kolesovs1 · Pavels Semjonovs1 Received: 1 July 2020 / Accepted: 16 September 2020 © Springer Nature B.V. 2020
Abstract Structurally diverse biopolymers, including extracellular polysaccharides (EPS), synthesized by bacteria can possess physicochemical and functional properties that make them important products of microbial synthesis with a broad and versatile biotechnological potential. Leuconostoc spp. belongs to the group of lactic acid bacteria as one of the predominant members and are relevant not only in varied food fermentations, but also can be employed in the production of extracellular homopolysaccharides (HoPS) such as α-glucans (dextran, alternan) and β-fructans (levan,inulin) from the sucrose-containing substrates. EPS are synthesized by specific Leuconostoc spp. extracellular glycosyltransferases [dextran sucrase, alternansucrase (ASR)] and fructosyltransferases (levansucrase, inulosucrase) and enzymatic reactions can be performed in whole culture systems as well as using cell-free enzymes. Both α-glucans and β-fructans have a wide range of properties, mostly depending on their pattern of linkages, which, although differing in some respects, make suitable prerequisites for their versatile application in many fields, especially in the food industry and biomedicine. As a rule, these properties (polymer type, molecular mass, rheological parameters), as well as the overall EPS yield, are strain-specific for the selected producers and depend to a large extent on the nutritional and growth conditions used, which in many cases remain not sufficiently optimized for Leuconostoc spp. This review summarizes the current knowledge on the potential of Leuconostoc spp. to produce commercially relevant EPS, including information on their applications in various fields, producer strains, production methods and techniques used, selected conditions, the productivity of bioprocesses as well as the possible use of renewable resources for their development. Keywords Alternan · Dextran · Exopolysaccharides · Inulin · Leuconostoc spp. · Levan
Introduction From the structurally diverse extracellular biopolymers synthesized by bacteria, their polysaccharide component is the most frequently represented and particularly functionally important one (Nwodo et al. 2012; Schmid et al. 2015). These extracellular polysaccharides (EPS) can either be attached to the bacterial cell surface or excreted into the growth medium and play an important role in cell protection against adverse environments, intercellular aggregation, surface adhesion and biofilm formation. On the other hand, EPS released into the environment can possess * Pavels Semjonovs [email protected] 1
Laboratory of Industrial Microbiology and Food Biotechnology, Institute of Biology, University of Latvia, Ojara Vaciesa str. 4, Riga 1004, Latvia
Probiotika LV, Ltd, Brivibas gatve 451, Riga 1024, Latvia
2
physicochem
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