Isolation and Characterization of Potential Anti-mycotoxigenic Bacteria from Traditional Fermented Food Products in Nigeria

Several bacteria species secrete bioactive compounds that are antagonistic to mold and their associated toxins which lead to food spoilage. Indigenous food sources serve as a reservoir for industrially relevant bacteria. This study aimed at screening for indigenous lactic acid bacteria from nono(Fermented cow milk) and African locust beans (dawadawa) that possess inhibitory activity against Aspergillus niger, the causative agent of Aflatoxicosis in food. 1ml of milk and 1g of mashed dawadawa samples were serially diluted onto cyclohexamide supplemented MRS agar plates. Sugar fermentation and growth pattern analysis at different pH, NaCl, temperatures and 16S rRNA sequencing using 27F/1492R primers were used for bacteria characterization. Pure isolates obtained were assayed for their activity against aflatoxin producing Aspergillus niger using the dual culture method. Plates were incubated at 25oC and monitored daily for percentage growth inhibition. Data obtained revealed a 16.6-53.3%, 6.6-50% inhibition of Aspergillus niger at 72 hours and a 41.6-71.6%, 16.6-68.5% growth inhibition of fungal growth at 120 hours for all isolates obtained from nono and dawadawa samples respectively. Growth pattern analysis revealed maximum bacteria growth after 96 hours at 33oC and 37oC from nono and dawadawa samples. All isolates exhibited growth in broth media containing 4.5% and 6.5% NaCl as well as in media at pH 4.5 and 9.6. Biochemical characterization revealed that all isolates were catalase negative with the ability to ferment sucrose, lactose, glucose and maltose, lactulose, trehalose and mannitol. Nucleotide sequence analysis identified these isolates as Bacillus cereus, Lactococcus lactis, Bacillus pumilus, Bacillus valismortis, Lactobacillus plantarum, Lactobacillus fermentum, Lactobacillus helveticus, Leuconostoc citreum and Lactobacillus delbruecki. The results of this study identified indigenous lactic acid bacteria as promising biological control agents for further testing against aflatoxicosis in food stuff