Pyrosequencing investigation into the influence of Cu(2+), Zn(2+), Fe(2+) and I(−) mixtures on fungal diversity and toxigenic fungal growth in a fermented liquid feed

A L(9)(3(4)) orthogonal experiment was conducted to evaluate the influence of 9 mixtures which consisted of Cu(2+), Zn(2+), Fe(2+) and I(−) ions at different ion concentrations on fungal diversity and toxigenic fungal growth in a Bacillus subtilis-fermented liquid feed (FLF) using pyrosequencing. The maximal Chao estimator and Shannon index were achieved in the FLF with a mixture of Cu(2+) (200 mg/kg), Zn(2+) (160 mg/kg), Fe(2+) (150 mg/kg) and I(−) (2.4 mg/kg). The minimal relative abundance of Aspergillus was achieved when a mixture of Cu(2+) (200 mg/kg), Zn(2+), Fe(2+) and I(−) was added to the FLF. Compared with Zn(2+), Fe(2+) and I(−), Cu(2+) was the most important ion in inhibiting Aspergillus growth. Adding Zn(2+) (160 mg/kg), Cu(2+), Fe(2+) and I(−) to the FLF minimized the relative abundance of Fusarium. It was Zn(2+) instead of Cu(2+) played a critical role in suppressing the growth of Fusarium. The proper use of the mixture of Cu(2+), Zn(2+), Fe(2+) and I(−) in FLF contributes to inhibit the growth of mycotoxin-producing fungi during storage. The new findings of this study help farmers properly use the mixture of Cu(2+), Zn(2+), Fe(2+) and I(−) to inhibit the growth of mycotoxin-producing fungi in the production of high quality FLF and alleviate mycotoxins damages to animals and humans.