Fermentation development using fruit waste-derived mixed sugars for antifungal equisetin production by Fusarium equiseti D39 and yield increase mechanism

Fruit waste is rich in sugars, trace elements, and other components that can serve as high-quality fermentation substrates for industrial production of natural products pesticides. In the present study, we use fruit waste to produce the high-value antifungal compound, equisetin, in a Fusarium equiseti D39 bioreactor, and the yield increase mechanism was clarified. Equisetin exhibited varying degrees of antifungal activity against seven pathogenic fungi, with EC₅₀ values ranging from 1.8 to 25.3 μg/mL, and could completely prevent grape gray mold in vivo experiment. Extracts from five types of fruit waste (apples, bananas, grapes, peaches, and watermelons) were evaluated as substrates for equisetin production. The high concentrations of fructose and starch in the apple extract were found to be beneficial for equisetin production, with a yield of 20.8 mg/L, and stimulated equisetin analogues production. Fructose increased equisetin yield by increasing synthetic substrates, improve the biological activity of key enzymes, and enhance the crucial genes expression in its biosynthetic pathway. Overall, the process yielded 10.7 mg of equisetin from 100 g of apples, illustrating the significant potential of this process for the valorisation of discarded fruit, and providing a route for the industrial production of natural product pesticides.