Structural and Rheological Properties of Exopolysaccharides Produced by Some Lactic Acid Bacterial Strains Isolated from Palm Wine

ABSTRACT

Aims: This study evaluated the physical, chemical and rheological properties of exopolysaccharides (EPSs) produced by Lactic Acid Bacteria (LAB) isolated from palm wine. Materials and Methods: EPSs from palm wine LAB strains were produced on 6% sucrose broth, purified and freeze-dried prior to analyses. Molecular weights (MW), rheological and structural composition (functional groups) of the EPSs were determined using standard methods and Fourier transform infrared spectroscopy (FTIR). Results: The average MW of the EPSs ranged from 2.02×106 to 6.53×106 Da while the flow index (n) values ranged from 0.03-3.13 at 0.2%, 0.06-1.51 at 0.4%, 0.38 - 1.85 at 0.6%, 0.14 - 2.26 at 0.8% and 0.55 - 6.42 at 1% concentrations at elevated temperatures for EPS solutions from the ten LAB species. The FTIR spectrum revealed prominent peaks of various groups of OH (3420 cm-1) and CH3 bending (2090 cm-1) in all the EPSs corresponding to both hydroxyl and amine groups, and aliphatic C-H bonds, respectively. EPS synthesized by Leuconostoc lactis, Lactococcus lactis subsp lactis and Lactiplantibacillus plantarum showed weak absorption peaks (1148 – 1145 cm-1) indicating the C-O-C and C-O bonds, while absorption peaks of Lactobacillus lactis, Lactobacillus acidophilus and Lactiplantibacillus plantarum (1267 – 1253 cm-1) indicated O- acetyl ester and other non-sugar components. Conclusions: The FTIR spectra, rheological properties and molecular weight of EPSs synthesized by the ten LAB strains indicated potentials that could be exploited in different industrial applications, and as stabilizers in food industries