Characterization of lactic acid bacteria from fermented cereal-based foods in Anyigba, Nigeria, for potential probiotic and bio-preservation applications

Abstract

Background: Traditional fermented cereal-based foods are dietary staples in Nigeria, as they provide essential nutrients and contribute to food security. These fermentations are primarily driven by Lactic Acid Bacteria (LAB), which are known for their health-promoting and bio-preservative properties. Despite their widespread consumption, a systematic phenotypic characterization of LAB from indigenous foods in specific regions is often overlooked. 

Objective: This study was based in Anyigba, Kogi State, Nigeria. It aimed to isolate, phenotypically characterize, and screen LAB strains from locally fermented cereal-based foods for their potential probiotic attributes and antimicrobial defenses against common foodborne pathogens. This study resorted to molecular methods to exploit microbial diversity for applied microbiological solutions.

Methods: A total of 15 samples of fermented cereal-based foods (ogi and kunu) were collected from local markets and households in Anyigba, Kogi State, Nigeria. LAB were isolated on de Man Rogosa Sharpe (MRS) agar. Presumptive LAB isolates were identified based on Gram staining, catalase negativity, and CO2 production from glucose. Selected isolates were further characterized for acid tolerance (pH 2.0 or 3.0 for 3 hours), bile salt tolerance (0.3% oxgall for 3 hours), auto-aggregation, co-aggregation with selected pathogens (Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923, Salmonella Typhimurium ATCC 14028), and antimicrobial activity against these pathogens using the agar well diffusion method. Hemolytic activity was also assessed on blood agar.

Results: Out of 98 distinct LAB isolates obtained, 78.6% demonstrated high survival rates (> 50%) after 3 hours at pH 3.0, and 65.3% survived 3 hours in 0.3% oxgall. Among 20 selected promising isolates, strong auto-aggregation (> 40%) was observed in 35.0% (7/20) of strains. Co-aggregation with E. coli, S. aureus, and S. Typhimurium ranged from 18-55% among these selected strains. Furthermore, 70.0% (14/20) of the selected isolates showed significant antimicrobial activity against at least one of the tested pathogens, with inhibition zones ranging from 10 to 22 mm. None of the selected isolates exhibited β-hemolytic activity.

Conclusion: The fermented cereal-based foods from Anyigba, Nigeria, are rich sources of diverse LAB strains possessing desirable probiotic characteristics, including robust acid and bile salt tolerance, significant aggregation abilities, and broad-spectrum antimicrobial activity against critical foodborne pathogens. These findings highlight the substantial potential of these indigenous LAB as promising candidates for the development of novel probiotic products in medical microbiology, as well as natural biopreservatives in the food industry and applied microbiology. These LAB strains have the potential to greatly contribute to enhanced food safety and human health, particularly within the Anyigba region of Nigeria.

Keywords: Lactic Acid Bacteria, Fermented Cereals, Probiotics, Antibiotics, Bio-preservation, Anyigba, Nigeria