Effect of temperature and water activity on the production of fumonisins by Aspergillus niger and different Fusarium species

In the present study, a screening of 5 A. niger strains and 25 assumed fumonisin producing Fusarium strains from 6 species, showed that all 5 A. niger strains produced FB2 and 23 of 25 Fusarium produced fumonisin B1 and other isoforms (fumonisin B2 and B3). Five A. niger and five Fusarium spp. were incubated at six different temperatures from 15-42°C on Czapek Yeast Agar +5% salt or Potato Dextrose Agar. A. niger had the highest production of FB2 at 25-30°C whereas Fusarium spp. had the maximal production of FB1 and FB2 at 20-25°C. Addition of 2.5-5% NaCl, or 10-20% sucrose increased the FB2 production of A. niger, whereas addition of glycerol reduced FB2 production. All three water activity lowering solutes reduced the fumonisin production of the Fusarium species.The present study shows that the regulation of fumonisin production is very different in A. niger and Fusarium, and that food and feeds preserved by addition of sugar or salts may be good substrates for fumonisin B2 production by A. niger.The fumonisins were discovered in 1988 and are divided in four series A, B, C, P [1-3]with the B1 (FB1), B2 (FB2) and B3 (FB3) as the most abundant naturally occurring homologues [4,5]. They were first isolated from Fusarium verticillioides (= F. moniliforme pro parte [6]) strain MRC 826 by Gelderblom et al. [7]. FB1 is mainly produced by F. verticillioides and F. proliferatum [8]. However, production of type B fumonisins by other Fusarium spp. has also been reported, e.g. from F. dlaminii, F. napiforme, F. nygamai and F. oxysporum [8-10]. Fumonisins are important mycotoxins because they are suspected to cause human and animal toxicoses by the consumption of contaminated corn-based food and feeds [11]. Fumonisins have been shown to induce outbreaks of equine leukoencephalomalacia in horses and pulmonary edema and hydrothorax in pigs [5,12]. The fumonisins are structurally similar to sphingolipids and have shown to inhibit the sphingolipid biosynthesis via the ceramide syn