Fungicide effect of a novelty antimicrobial biosurfactant extract alone or combined with copper oxychloride on Botrytis cinerea cells

Abstract

Microbial contaminations represent an important issue for crop production, resulting in tons of losses worldwide every year. One of the highest-risk pathogens involved in these infections is Botrytis cinerea, which is responsible for the grey mold disease. In this study, a biosurfactant extracted from corn steep liquor (CSL), an agro-industrial residue from the corn-milling industry, was used in combination with copper oxychloride (Cu-Oxy), a copper-based pesticide, to evaluate their fungitoxic activity on B. cinerea cells. The results showed that the mixture of 2 g/L of Cu-Oxy with 16 g/L of the biosurfactant extract from CSL, named biosurfactant pesticide formulation (BS-P), helped in the reduction of colony growth, in the decrease of biomass production, and in the improvement of copper bioaccumulation on fungal mycelium in comparison with aqueous solutions of commercial and pure-copper-based fungicides. A factorial design was conducted to obtain the best operational conditions for enhancing the bioaccumulation of copper by B. cinerea cells in the presence of BS-P, resulting in a maximum copper uptake of 2122 µg Cu/g dry weight when using 1 g/L of Cu-Oxy combined with 8 g/L of CSL biosurfactant extract at an incubation temperature of 15 °C. It was also proved that, due to the absence of the biosurfactant extract, the amount of copper bio-adsorbed by fungal mycelium was considerably decreased and, therefore, so was its fungitoxic activity. These results suggest that the biosurfactant extract studied could be involved in eco-friendlier pesticide formulations, reducing the environmental impact of copper-based active principles.