Evaluation of the Efficiency of Ethanol Precipitation and Ultrafiltration on the Purification and Characteristics of Exopolysaccharides Produced by Three Lactic Acid Bacteria

Abstract

Exopolysaccharides (EPS) produced by three Lactic Acid Bacteria strains,Lactococcus lactisSLT10,Lactobacillus plantarumC7, andLeuconostoc mesenteroidesB3, were isolated using two methods: ethanol precipitation (EPS-ETOH) and ultrafiltration (EPS-UF) through a 10 KDa cut-off membrane. EPS recovery by ultrafiltration was higher than ethanol precipitation forLactococcus lactisSLT10 andLactobacillus plantarumC7. However, it was similar with both methods forLeuconostoc mesenteroidesB3. The monomer composition of the EPS fractions revealed differences in structures and molar ratios between the two studied methods. EPS isolated fromLactococcus lactisSLT10 are composed of glucose and mannose for EPS-ETOH against glucose, mannose, and rhamnose for EPS-UF. EPS extracted fromLactobacillus plantarumC7 andLeuconostoc mesenteroidesB3 showed similar composition (glucose and mannose) but different molar ratios. The molecular weights of the different EPS fractions ranged from 11.6±1.83 to 62.4±2.94 kDa. Molecular weights of EPS-ETOH fractions were higher than those of EPS-UF fractions. Fourier transform infrared (FTIR) analysis revealed a similarity in the distribution of the functional groups (O-H, C-H, C=O, -COO, and C-O-C) between the EPS isolated from the three strains.