Antimicrobial properties, safety, and probiotic attributes of lactic acid bacteria isolated from Sauerkraut

Abstract

Background: According to the World Health Organization, probiotics have been defined as live microorganisms that when administered in the right amount provide health benefits to the host. This study aims to isolate lactic acid bacteria (LAB) from Sauerkraut and determine their anti-pathogenic potential and suitability as probiotics.

Methodology: Lactic acid bacteria (LAB) were isolated from fermented cabbage obtained from an open market in Akure, Ondo State, Nigeria by inoculating the prepared cabbage suspension on triplet plates of Rogosa agar (Lactobacillus selecting agar) and incubating in an anaerobic jar with gaspaks at 37°C for 72 hours. The LAB isolates were presumptively identified phenotypically by colony morphology, Gram stain reaction, and catalase test. The antibacterial activity of the LAB isolates was then carried out using agar overlay and agar-well diffusion methods. The most efficient LAB isolate was selected based on its strong antibacterial activity, confirmed by 16S rRNA sequencing and further evaluated for probiotic activities including bile salt resistance, survival in low pH, hydrophobicity of the cell surface, auto-aggregation, and co-aggregation. The putative probiotic LAB isolate was also evaluated for its safety using in vitro tests (antibiotic susceptibility testing, haemolysis, and DNase tests) and in vivo assays (sub-acute oral toxicity tests in male albino rats).

Results: A total of 5 LAB isolates were preliminarily identified from the cabbage. The LAB isolate that showed strong antibacterial activity was confirmed as Levilactobacillus brevis. The isolate showed 83.3% survival rate in low pH of 3 and 85.9% in 0.3% bile concentration indicating potential tolerance to gastrointestinal conditions. The cell surface hydrophobicity assay showed 51% and auto-aggregation of 60% which represents the adhesion properties of the isolate. The sub-acute oral toxicity evaluation of the putative probiotic strain in Wister albino rats showed no altered health condition.

Conclusion: The findings in this study suggest that Levilactobacillus brevis isolated from Sauerkraut is suitable as probiotics and could be applied in the pharmaceutical and food industry.