Production of exopolysaccharides by lactic acid bacteria isolated from traditional fermented foods in Nigeria

Lactic acid bacteria isolated from traditional fermented foods in Nigeria were investigated for their ability to produce exopolysaccharides (EPS). The test organisms were chosen after screening in a modified exopolysaccharide selection medium (mESM). The ability of the test organisms to produce EPS in whey medium (WM) and supplemented whey media (SWM I, SWM II) with combinations of lactose, KH₂PO₄, NH₄Cl, casamino acids, mineral salts and yeast extract was determined. Amongst the test isolates, only Leuconostoc mesenteroides (from sorghum ogi) and Lactobacillus plantarum (from maize ogi) demonstrated the highest form of EPS production. Adjustment of the pH of SWM II to 6.2 increased the viscosity relative to that of SWM I (5.7) that was not adjusted. The effect of incubation temperature showed that at 25 °C, the viscosity was higher for L. mesenteroides and L. plantarum than at 30 and 40 °C. However, the biomass yield was lower, the least lactose was utilized and less lactic acid was produced at this temperature. More galactose and glucose were liberated at 30 °C that at 25 and 40 °C. This paper suggested that the viscous nature of some traditional foods in sub-Saharan Africa may be partly due to excretion of polysaccharides during the fermentation processes.