Microbiological Characterisation of Fermented Locust Beans (Iru) Produced in Kwara State

Iru, a fermented locust bean condiment widely consumed as a flavour enhancer across West Africa, has significant nutritional value but its microbial safety profile varies with traditional production practices in different Nigerian communities. This study characterises the microorganisms associated with fermented locust beans produced by traditional processors in Kwara State, North Central Nigeria. Twelve iru samples at different stages of fermentation (24 hours, 48 hours, and 72 hours) were collected from processors in Ilorin and Offa local government areas. Standard pour plate, selective media isolation, and biochemical characterisation were used to identify bacteria and fungi at each fermentation stage. Bacillus subtilis was the dominant fermentative organism at all stages, constituting 58 percent of isolates at peak 48-hour fermentation. Bacillus licheniformis, Enterococcus faecalis, and Micrococcus species were co-isolates. Enterobacteriaceae were most prevalent at 24 hours and declined sharply by 72 hours, suggesting competitive exclusion by Bacillus species during active fermentation. Aspergillus and Penicillium species were isolated from improperly stored finished products. Aflatoxin screening by thin layer chromatography showed no detectable aflatoxin in freshly fermented samples, but positive results in three stored samples. The study recommends hygienic storage containers, controlled fermentation conditions, and education of Kwara State iru processors on safe handling practices to prevent aflatoxin accumulation. Keywords: iru, fermented locust bean, Bacillus subtilis, fermentation microbiology, Kwara State