Antagonistic properties of microogranisms associated with cassava (Manihot esculenta, Crantz) products

The antagonistic properties of indigenous microflora from cassava starch, flour and grated cassava were investigated using the conventional streak, novel ring and well diffusion methods. Antagonism was measured by zone of inhibition between the fungal plug and bacterial streak/ring. Bacillus species were more effective to inhibit the growth of Aspergillus niger, A. fumigatus, Fusarium moniliforme and Rhizoctonia sp. Pseudomonas fluorescens, Escherichia coli and Saccharomyces sp. inhibited the growth of A. niger, A. flavus and F. moniliforme. There were considerable variations in inhibitory activity. The zone of inhibition was more apparent in the novel ring method. Percentage inhibition increased to 78% in the Ring method and 62% in streak method after 168 h of incubation. Lactobacillus brevis, L. acidophilus and Bacillus subtilis inhibited the growth of E. coli and Staphylococcus aureus. Inhibition of the pathogenic microorganisms was probably due to the production of organic acids and bacteriocins.