Probiotic and Bacteriocino genic Potential Of Lactic Acid Bacteria of Fermented Foods And Beverages Origin

Abstract

Food quality, safety, flavor, and aroma are improved by metabolites produced by lactic acid bacteria (LAB) that include organic acids, bacteriocins, and hydrogen peroxides. The metabolites could inhibit the growth of food borne pathogens and spoilage microorganisms in foods. Furthermore, LAB play a crucial role in the fermentation process by giving unique flavors and textures to food products, prolonging its shelf life, emhancing safety and quality. LAB also have probiotic roles that effectively combat foodborne pathogens. LAB have gained attention for bacteriocin production and their biopreservative properties. Thus, the objective of this study was to isolate and characterize LAB retrieved from Ethiopian traditional fermented foods and beverages for their probiotic, bacteriocin production, and preservative activities. In addition, the study was conducted to assess the bio preservative potential of LAB in milk, fruits, and vegetables. Traditional fermented foods and beverages were collected from East Wollega Zone and Jimma Town. About, 180 samples, 30 each (kotcho, bulla, borde, shamita, bukuri, and ergo) were collected and transported to Jimma University's Microbiology Laboratory for isolation of LAB following standard methods. LAB isolates were characterized using morphological, biochemical, physiological, and MALDI ToF/Ms techniques. Concurrently, the effects of acid, temperature, enzymes, and food preservatives on the antagonistic activities of LAB strains were evaluated. The study further evaluated potential probiotic LAB based on their tolerance to bile salt and acid, gastrointestinal simulation, auto- and co-aggregation, hydrophobicity, antibiotic resistance, bacteriocin production, and bio-preservation activity. The bacteriocin assay was evaluated at various temperatures, incubation times, and growth medium to determine the optimal conditions for bacteriocin production. Solvent extraction methods for concentrating of bacteriocins were developed, and various extraction procedures were tested for successful bacteriocin recovery. The ability of the LAB isolates to prolong the shelf life of test foods was evaluated. About, 956 LAB isolates were recovered from 180 traditional fermented food and beverage samples. As revealed from phenotypic and morphological characteristics, Lactobacillus, Lactococcus, Streptococcus, Pediococcus, and Enterococcus species dominated all the six traditional fermented foods and beverages. Lactobacillus was the most abundant genus with even distribution in all the traditional fermented foods and beverages. Bulla harbored the highest number of LAB communities, followed by Ergo. Over 580 of the 956 isolates showed strong inhibitory activity against selected food borne pathogens. Furthermore, 340 LAB had antagonistic effects against all the selected food borne pathogens. Using MALDI-ToF/MS analysis, the majority of the isolates were identified as Pediococcus species (P. acidilactici and P. pentosaceus) followed by Enterococcus species mainly E. Page xviii of 255 faecium (n = 6), Lactococcus lactis (n = 2), Bacillus species (B. infantis), and Rothia dentocariosa (n=1)). Pediococcus pentosaceus (23.33%) dominated the microbial ecology of all the selected Ethiopian traditional fermented foods and beverages followed by Enterococcus faecium (20%), and the least common species was Lactococcus lactis (6.67%). All of the isolates, 17 of them showed potential capacity to produce antimicrobial activity, putative bacteriocins, survive in simulated gastrointestinal tracts, and inhibitor substances were all studied in vitro and in artificially simulated environments. Out of 340 that demonstrated potential antagonistic effects, 44 (13%) of isolates survived at pH 2 and 3 for 3 and 6 h, respectively, with survival rates ranging from 33.825% to 100%. Because they were acid- and bile-tolerant isolates, 125 of the 340 LAB isolates were screened as potential probiotic candidates. Among 125 isolates, 39 (31.20 %) were identified as the best acid and bile salt-tolerant, with the potential capacity to produce bacteriocin. All the thirty-nine promising bacteriocin producers were susceptible to tetracycline (30 g/ml) and chloramphenicol (15 g/ml), but highly resistant to kanamycin (20 g/ml), with some being resistant or susceptible to streptomycin (10 g/ml) and ampicillin (10 g/ml). Additionally, the isolates showed nearly 75%–95% survival rates at low pH (2, 2.5, and 3), bile salt (0.3%), intestinal inhibitor substances, and simulated gastro-intestinal conditions, respectively. The potent isolates also showed strong potency for aggregation (50-120 %) and cell surface hydrophobicity (70-116%). P. pentosaceus JULABB16 was identified as the most effective isolate in controlling the spoilage microorganisms and extended the shelf life of tested fruits and vegetables by at least thee weeks. Likewise, Lactococcus lactis was found to be the potential isolate to maintain the quality of milk. The entire potent and selected LAB demonstrated potential preservative efficiency because they did not cause browning or off-odor on fruits and vegetables for thee to four weeks. In conclusion, this study demonstrates the significant potential of lactic acid bacteria (LAB) to extend the shelf life of fruits, milk, and vegetables. The research has established a foundation for the selection of specific antimicrobial peptides and the further development and application of LAB for antibacterial and probiotic activities. The findings underscore the efficacy of certain LAB isolates in enhancing the longevity and safety of various food products. Moving forward, further research should focus on the practical applications of these LAB isolates in food preservation strategies and probiotic formulations, aiming to leverage their full potential in extending shelf life and promoting health benefits.