The inhibitory potential of dominating yeasts against moulds in maize fermentation

Abstract

The inhibitory effects of the dominating yeasts from different stages of kenkey production i.e. Candida krusei (35 isolates) and Saccharomyces cerevisiae (29 isolates) against 3 moulds Penicillium citrinum, Aspergillus flavus and Aspergillus parasiticus were investigated. Distinct growth inhibitory effects of the two yeasts was demonstrated against all isolates of the 3 mould species obtained from maize as well as mycotoxin producing strains (15) of the same mould species. The Candida isolates were found to have a greater inhibitory potential than the Saccharomyces isolates. The Penicillium spp. were more sensitive to the yeasts than the Aspergillus spp. Preliminary investigations to determine the mechanism of inhibition indicated that mould growth was not affected by either yeast supernatant or cell free extracts suggesting that the inhibitions were not due to compounds produced by the yeasts. It was concluded that the inhibitory potential of the yeasts was due to competition for nutrients between the yeasts and the moulds