Synergism between nisin and citronellal against Fusarium graminearum and their application in maize preservation

Fusarium graminearum (F. graminearum), responsible for Fusarium head blight in cereals, causes significant yield losses and produces mycotoxins contaminating food and feed. The combined effects of nisin and citronellal against F. graminearum were investigated in this study. The combination of nisin and citronellal not only exhibited a synergistic effect against F. graminearum spores (FICI <0.3125), but also significantly inhibited mycelial growth, with inhibition rates of (76.93 ± 6.74) % and (95.24 ± 4.33) % for mycelial diameter and weight, respectively. The nisin/citronellal combination maintained stable antifungal activity independent of salts, high temperature, and acid–base conditions. Mechanistically, citronellal strongly inhibited energy metabolism, nisin significantly reduced the ergosterol content (to our knowledge, the first report of nisin suppressing ergosterol in F. graminearum), and the combination of citronellal and nisin further enhanced disruption of fungal cell membranes. Moreover, due to the reduced dosage and involvement of multiple mechanisms, the nisin/citronellal combination did not induce resistance in F. graminearum after 30 generations, with MIC fold changes of 0.25 to 2. Finally, the combination effectively suppressed fungal contamination in maize. Overall, nisin and citronellal could be used together for controlling F. graminearum in food and feed industries. Although the production costs of nisin and citronellal remain higher than those of synthetic fungicides, the continuous development of biotechnology is driving their application in post-harvest grain storage.