Characterisation of Lactic Acid Bacteria Isolated from Fermented Locust Bean (Iru) and Their Potential as Starter Cultures in Niger State

Locust bean fermentation is driven by diverse microbial communities whose composition significantly influences product quality, safety, and consistency. The use of defined starter cultures offers a pathway to standardising fermentation outcomes in commercial iru production. This study characterised lactic acid bacteria isolated from spontaneously fermented iru produced in three communities in Niger State, North Central Nigeria, and evaluated their potential as starter culture candidates. A total of 94 lactic acid bacteria isolates were obtained from ten fermentation samples collected at 24, 48, and 72-hour intervals. Isolates were characterised by phenotypic methods and identified to species level using 16S rRNA gene sequencing. Technological properties assessed included acid tolerance, bile salt tolerance, bacteriocin production, proteolytic activity, and aroma compound production. Safety evaluation involved assessment of haemolytic activity and antibiotic resistance profiling using disc diffusion. Results identified Lactobacillus plantarum, Leuconostoc mesenteroides, and Lactobacillus fermentum as the dominant species. Three isolates of Lactobacillus plantarum demonstrated superior acid tolerance (survival at pH 2.5), moderate bile salt resistance (0.3 percent bile), and significant proteolytic activity associated with umami flavour development. None of the selected strains exhibited haemolytic activity or resistance to clinically critical antibiotics. The study identifies three candidate lactic acid bacteria isolates from Niger State iru for further starter culture development and controlled fermentation trials. Keywords: lactic acid bacteria, starter cultures, iru, fermentation, Niger State.