Characterization of dextrans produced by Lactobacillus mali CUPV271 and 1 Leuconostoc carnosum CUPV411 2

20 The exopolysaccharide (EPS)-producing carnosum CUPV411 were isolated from Spanish ropy apple must and slimy ham, 22 respectively. The polymers were purified from bacterial cultures’ supernatants and 23 subjected to physicochemical and rheological characterization with the aim to evaluate 24 their potential for future industrial utilization. Methylation analysis, Fourier-Transform 25 Infrared Spectroscopy (FT-IR) and Nuclear Magnetic Resonance (NMR) revealed that 26 both polymers were dextrans, partially branched at O -3 and O -4 positions of the main α- 27 (1→6)- D -glucopyranose backbone. The molar masses of the EPS of L. mali and Lc. 28 carnosum, were of 1.23 x 10 8 g/mol and 3.58 x 10 8 g/mol, respectively. The bacterial 29 strains were tested for binding to the human Caco-2 cell line in the presence and 30 absence of their respective dextran, revealing that the EPS production by L. mali 31 decreased the binding capacity of the bacterium while the adhesiveness of Lc. carnosum 32 did not change. As the structure and molecular mass of both dextrans were comparable, 33 other characteristics of the dextrans were studied to explain this behavior. Atomic force 34 micrographs showed some differences at the supramolecular level, suggesting that the 35 different spatial distribution of the dextrans might be on the basis of the results of the 36 adhesion studies. Both polysaccharides resulted to be amorphous materials with T g 37 around 226 °C and showed slightly different thermal degradation patterns. 38 Rheologically, they showed to have a pseudoplastic behavior, but very different critical 39 concentrations: 3.8% for the EPS of L. mali and 0.4% for that of Lc. carnosum .