Influence of lactic acid bacteria on fungal growth and aflatoxin production in ogi, an indigenous fermented food

Antagonistic activity of lactic acid bacteria against some fungal isolates was investigated using both overlay and agar well diffusion methods. With overlay method, L. plantarum K1 showed very strong antagonistic activities against Aspergillus flavus BMO36 and Rhizopus stolonifer BMOO2 with 25 mm and 20 mm zones of inhibition, respec-tively. The selected Lactic acid bacteria (LAB) produced lactic acid, hydrogen peroxide, diacetyl and bacteriocin. L plantarum K1 produced the highest quantity (2.48g/l) of lactic acid, while Pediococcus halophilus C4 produced the lowest one, but the highest quantity (3.44g/l) of diace-tyl. Hydrogen peroxide production increased with time, and the production peak was recorded at 72 hours incuba-tion period. The entire three selected LAB produced bac-teriocin that inhibited the growth of various fungi using agar-well diffusion method, and, therefore, overlay method seemed to be a better procedure. Lactobacillus plantarum k1 was found to inhibit the production of aflatoxins B and G by Aspergillus flavus, when used as starter culture in the fermentation of cereal gruel (ogi).