Dextrans synthesised by three Leuconostoc mesenteroides strains, isolated from mammalian milks, were studied and compared with dextrans produced by Lc. mesenteroides and Lactobacillus sakei strains isolated from meat products. Size exclusion chromatography coupled with multiangle laser light scattering detection analysis demonstrated that the dextrans have molecular masses between 1.74x10(8)Da and 4.41x10(8)Da. Rheological analysis of aqueous solutions of the polymer revealed that all had a pseudoplastic behaviour under shear conditions and a random, and flexible, coil structure. The dextrans showed at shear zero a difference in viscosity, which increased as the concentration increased. Also, the purified dextrans were able to immunomodulate in vitro human macrophages, partially counteracting the inflammatory effect of Escherichia coli O111:B4 lipopolysaccharide. During prolonged incubation on a solid medium containing sucrose, dextran-producing bacteria showed two distinct phenotypes not related to the genus or species to which they belonged. Colonies of Lc. mesenteroides CM9 from milk and Lb. sakei MN1 from meat formed stable and compact mucoid colonies, whereas the colonies of the other three Leuconostoc strains became diffuse after 72h. This differential behaviour was also observed in the ability of the corresponding strains to bind to Caco-2 cells. Strains forming compact mucoid colonies showed a high level of adhesion when grown in the presence of glucose, which decreased in the presence of sucrose (the condition required for dextran synthesis). However no influence of the carbon source was detected for the adhesion ability of the other Lc. mesenteroides strains, which showed variable levels of binding to the enterocytes.

Lactic acid bacteria, exopolysaccharides, adhesion, Dextran, Leuconostoc mesenteroides, immunomodulation, Rheological properties

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

Warning = sub-repeat ending at aDGlcp: large unit count (86) was reduced to 5
Warning = sub-repeat ending at aDGlcp: large unit count (86) was reduced to 5
Warning = sub-repeat ending at aDGlcp: large unit count (86) was reduced to 5
[*]OC[C@H]1O[C@H](OC[C@H]2O[C@H](OC[C@H]3O[C@H](OC[C@H]4O[C@H](OC[C@H]5O[C@H](OC[C@H]6O[C@H](OC[C@H]7O[C@H]([*])[C@H](O)[C@@H](O[C@H]8O[C@H](CO)[C@@H](O)[C@H](O)[C@H]8O)[C@@H]7O)[C@H](O)[C@@H](O)[C@@H]6O)[C@H](O)[C@@H](O)[C@@H]5O)[C@H](O)[C@@H](O)[C@@H]4O)[C@H](O)[C@@H](O)[C@@H]3O)[C@H](O)[C@@H](O)[C@@H]2O)[C@H](O)[C@@H](O)[C@@H]1O

1297.128 g/mol (C₄₈H₈₀R₂O₄₀, R = next and previous repeats, not counted in mol weight)

Paenibacillus polymyxa 92, isolated from wheat roots, produced large amounts (38.4 g L-1) of exopolysaccharide (EPS) in a liquid nutrient medium containing 10 % (w/v) sucrose. The EPS was precipitated from the culture broth with cold acetone and was purified by gel filtration and anion-exchange chromatography. The molecular mass of the EPS was 2.29-1.10 × 105 Da. Diffuse reflectance infrared Fourier transform and nuclear magnetic resonance spectra showed that the EPS was a linear β-(2→6)-linked fructan (levan). Aqueous EPS solutions showed pseudoplastic behavior when shear stress was applied at different temperatures. By using the Ostwald-de Waele model, the rheological characteristics of the EPS solution were ascertained. The sorption capacity of the EPS for Zn(II), Cd(II), Pb(II), and Cu(II) was investigated. Sorption was maximal (q = 481 mg g-1) for Cu(II) ions. In model experiments, treatment of wheat seeds with EPS solution significantly increased the length of seedling roots and shoots.

exopolysaccharide, Rheology, levan, Paenibacillus polymyxa, Plant-growth-promoting activity

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
	bDFruf	61.7	105.3	78.0	76.7	81.4	64.6


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
	bDFruf	3.70-3.77	-	4.19	4.09	3.95	3.60-3.90


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
	bDFruf	61.7/3.70-3.77		78.0/4.19	76.7/4.09	81.4/3.95	64.6/3.60-3.90

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

[*]OC[C@H]1O[C@]([*])(CO)[C@@H](O)[C@@H]1O

162.141 g/mol (C₆H₁₀R₂O₅, R = next and previous repeats, not counted in mol weight)