Probiotic Properties and Safety Profiling of <i>Lactobacillus plantarum</i> Isolated from Spontaneously Fermented Milk in Kenya

Abstract

The aim of this study was to assess the probiotic potential and safety profile of a Lactobacillus plantarum strain isolated from Kenyan spontaneously fermented milk, Amabere amaruranu. The Lactobacillus plantarum isolate was tested for temperature sensitivity (at 15°C, 30°C, 37°C, and 45°C), pH tolerance (at 2.0, 2.5, 3.0, 3.5, and 6.5 as control), and 0.4% phenol tolerance to observe its survival in the gastrointestinal tract of humans. For safety evaluation of the isolate, antagonistic activity was tested against pathogenic strains of Staphylococcus aureus, Escherichia coli, Salmonella enterica serovar Typhi, and Candida albicans, while antibiotic susceptibility pattern was examined using nalidixic acid, ampicillin, azithromycin, ciprofloxacin, tetracycline, gentamicin, and chloramphenicol antibiotic discs and haemolytic activity was done using lamb blood agar. Lactobacillus plantarum isolate had an optimal growth at 37°C, it also demonstrated low pH tolerance (2.0–3.5). It was able to maintain its viability (~100%) after exposure to 0.4% phenol. The selected isolate showed inhibition (antagonistic activity) against the pathogens with S. typhi having the largest (ZDI = 31.0 ± 1.73 mm) zone of diameter inhibition (ZDI) and Candida albicans having the least (ZDI = 18.0 ± 0.76 mm). Lactobacillus plantarum isolate was sensitive to Azithromycin, tetracycline and chloramphenicol and was intermediately sensitive to gentamycin, while it was resistant to nalidixic acid, ampicillin, and ciprofloxacin. The isolate also exhibited γ-haemolytic activity hence safe for use as a starter culture. The selected isolate can be used as a starter culture and a probiotic since it had excellent probiotic properties.