GROWTH OF FUSARIUM-MONILIFORME AND ITS BIOSYNTHESIS OF FUMONISIN B1 ON MAIZE GRAIN AS A FUNCTION OF DIFFERENT WATER ACTIVITIES

The production of fumonisin by Fusarium moniliforme during its growth on maize depends on extrinsic factors. In particular, experiments on maize grain at different water activities (a(w)) (1, 0.95, 0.90, 0.85) have demonstrated the influence of a(w) on fumonisin biosynthesis, and on fungal growth defined by measurement of ergosterol levels. Fumonisin levels dropped threefold when a(w) was lowered by 5%, but growth rate was unchanged. A 10% reduction in a(w) from 1 to 0.90 resulted in a 20-fold drop in fungal growth, and fumonisin production was reduced 300-fold. At a threshold a(w) of 0.85-0.86, F. moniliforme exhibited virtually no measurable metabolic activity, and hence no fumonisin production.