Characterization of dextrans produced by Lactobacillus mali CUPV271 and Leuconostoc carnosum CUPV411
2019
Llamas-Arriba, María Goretti | Puertas, Ana I. | Prieto, Alicia | López, Paloma | Cobos, Mónica | Miranda, José I. | Marieta, Cristina | Ruas-Madiedo, Patricia | Dueñas, Ma Teresa
The exopolysaccharide (EPS)-producing Lactobacillus mali CUPV271 and Leuconostoc carnosum CUPV411 were isolated from Spanish ropy apple must and slimy ham, respectively. The polymers were purified from bacterial cultures’ supernatants and subjected to physicochemical and rheological characterization with the aim to evaluate their potential for future industrial utilization. Methylation analysis, Fourier-Transform Infrared Spectroscopy (FT-IR) and Nuclear Magnetic Resonance (NMR) revealed that both polymers were dextrans, partially branched at O-3 and O-4 positions of the main α-(1 → 6)-d-glucopyranose backbone. The molar masses of the EPS of L. mali and Lc. carnosum were of 1.23 × 108 g/mol and 3.58 × 108 g/mol, respectively. The bacterial strains were tested for binding to the human Caco-2 cell line in the presence and absence of their respective dextran, revealing that the EPS production by L. mali decreased the binding capacity of the bacterium while the adhesiveness of Lc. carnosum did not change. As the structure and molecular mass of both dextrans were comparable, other characteristics of the dextrans were studied to explain this behavior. Atomic force micrographs showed some differences at the supramolecular level, suggesting that the different spatial distribution of the dextrans might be on the basis of the results of the adhesion studies. Both polysaccharides resulted to be amorphous materials with Tg around 226 °C and showed slightly different thermal degradation patterns. Rheologically, they showed to have a pseudoplastic behavior, but very different critical concentrations: 3.8% for the EPS of L. mali and 0.4% for that of Lc. carnosum.
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