Exopolysaccharide (EPS) producing lactic acid bacteria (LAB) strain GA44 isolated from gari (a Nigerian traditional fermented cassava mash) was identified with 16S rRNA gene sequencing as Weissella cibaria. The EPS produced mainly composed of glucose and rhamnose sugar units and its molecular mass was about 2.8 Â 10 5 Da. The fourier-transform infrared (FT-IR) spectrum analysis showed characteristics absorption peaks indicating the presence of eOH, C¼O and C-H groups. Central composite design (CCD) and response surface methodology (RSM) were used to study the interactive effect of the significant factors on EPS yield. Under optimum conditions, the predicted maximum EPS produced 4.88 g/L while the actual experimental value was 4.80 g/L. The in-vitro antioxidant activities of the EPS showed good scavenging effects on superoxide anion radical and hydroxyl radical. The characteristics of this EPS isolated from food source will be useful in food industries and could also serve as a potential antioxidant.
The present study aims to evaluate the probiotic potential and technological properties of exopolysaccharide (EPS) producing lactic acid bacteria (LAB) isolated from Nigerian fermented cereal-based foods. Sixty-three autochthonous LAB isolated from cereal-based fermented foods were screened for EPS production, five isolates produced an appreciable amount of EPS on sucrose modified media and were identified by sequencing the 16S rRNA gene as L.plantarum YO175, L.plantarum OF101, P. pentosaceus OF31, W. confusa OF126 and W. confusa WS90. These five isolates were assessed for their probiotic and technological properties viz., tolerance to low pH, bile salt resistance, bile salt hydrolysis, tolerance to simulated gastric transit, cell surface hydrophobicity, antimicrobial, amylolytic and acidifying activity. The LAB isolates showed good survival at pH 2.0 and 2.5 and were resistant to 0.3% bile salt after 4 h. All the isolates tolerate gastric juice condition, with no reduction in viability except W. confusa WS90 that lost viability over 180 min incubation time. L. plantarum OF101 showed the highest hydrophobicity values for n-hexadecane and xylene (43.6%, 46.2%). They all showed different antimicrobial activities against five food-borne pathogens. P. pentosaceus OF31 possessed the highest ability to inhibit pathogens and also demonstrated better and rapid acid production capability. Albeit the properties tested are strain-dependent, L. plantarum and P. pentosaceus strains were found to possess interesting functional and probiotic characteristics to a greater extent compared to W. cibaria strains. The safety investigations indicate their suitability as good candidates for cereal-based probiotic products/starter culture for the improvement of traditional cereal fermentation process and also the development of functional cereal foods.
Fermented foods and beverages are mainly consumed by the indigenous people of Africa and other developing countries. Traditional fermentation is an age-long means of preserving perishable foods especially when other methods of preservation are not available and/or not consistent. The main beneficial microorganisms that are responsible for the fermentation of African indigenous fermented foods and beverages are lactic acid bacteria and yeasts which may be present as microflora on the substrates or added as starter cultures. The understanding of the synergistic interaction between these microorganisms in the fermented food matrices result in improved nutrient availability, food quality, palatability, organoleptic properties, increased shelf life, safety, digestibility and also play beneficial roles in modulating host immune system thereby minimizing the risk of certain diseases.
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