Antagonistic effects of raffia sap with probiotics against pathogenic microorganisms

Introduction. Probiotics are known for their beneficial properties. Numerous studies have been conducted to find advantages that probiotics can provide. This study aimed to evaluate the functional properties of raffia sap, a Cameroonian drink, fermented with probiotics by investigating its antagonistic activity against pathogenic bacteria. Study objects and methods. The study objective was raffia sap fermented by Lactobacillus fermentum and Bifidobacterium bifidum. Box-Behnken design with four factors (seeding rates of L. fermentum and B. bifidum, temperature, and incubation time) was used to generate mathematical models. The disc diffusion method was used to evaluate an antagonistic effect of the probiotics against four pathogenic bacteria (Escherichia coli, Listeria monocytogenes, Salmonella sp., and Bacillus cereus). An optimization of mathematical models of the inhibition diameters allowed to determine the optimal conditions of antagonistic effect. Results and discussion. The experimental data showed that zones of inhibition were 0‒21 mm for Salmonella sp., 0‒23 mm for E. coli, 0‒20 mm for L. monocytogenes, and 0‒22 mm for B. cereus. ANOVA results and the mathematical models obtained showed that L. fermentum was effective against B. cereus and B. bifidum against Salmonella sp., E. coli, and B. cereus. The optimization of the models revealed maximum zones of inhibition at the seeding rates of L. fermentum and B. bifidum of 2 and 10%, respectively, incubation time of 48 h, and temperature of 37°C. Conclusion. Raffia sap fermented by L. fermentum and B. bifidum demonstrated antagonistic effect against pathogenic bacteria such as E. coli, L. monocytogenes, Salmonella sp., and B. cereus.