Efficacy of antioxidant mixtures on growth, fumonisin production and hydrolytic enzyme production by Fusarium verticillioides and F. proliferatum in vitro on maize-based media

The effect of single or mixtures of antioxidants on the lag phase prior to growth, growth rate, hydrolytic enzyme production (N-acetyl-beta-glucosaminidase, beta-D-glucosidase and alpha-D-galactosidase) and fumonisin production by Fusarium verticillioides and F. proliferatum was evaluated on maize-based media at 25 degreesC, and under different water activity (a(w)) conditions. An increase in the lag phase (h) was observed for both F. verticillioides and F. proliferatum especially with propyl paraben (PP)+butylated hydroxyanisole (BHA) treatments at all a, levels tested. For both species PP alone or in combination with BHA, at concentrations of 0.5 and I mm reduced the growth rates by > 85 % at the three a, levels tested (0.995; 0.98 and 0.95). PP+butylated hydroxytoluene (BHT) or trihydroxybutyrophenone (THBP) were less effective in controlling growth, regardless of a, level. Combinations of PP+BHA reduced the fumonisin concentrations produced by F. verticillioides and F. proliferatum at 0.995 and 0.98 a, significantly. However, at low concentrations of antioxidants (0.5 mm) some stimulation in fumonisin production was observed with some treatments. The efficacy of the treatments was reflected in the impact on enzyme production. In the untreated control the highest total enzyme activity of three hydrolytic enzymes was observed at 0.995 a, after 96 h. All the antioxidant treatments alone or combined resulted in a significant reduction (P < 0.001) of the total enzyme activity at the aw levels tested. Only 10 mm THBP produced an increase in the total amount of N-acetyl-beta-D-glucosidase by both F. verticillioides and F. proliferatum. For the three enzymes single factors: time, a, and antioxidant treatments, most two and all three way interactions were significant (P < 0.001). The use of combined mixtures of antioxidants could be a good strategy to diminish the entry of fumonisin into the animal feed and human food chains.