ROS/ER-UPR Signaling-Mediated Inhibition of Cyclo(l-Anthraniloyl-l-Pro) on Penicillium expansum and Its Application in Controlling Blue Mold.

Penicillium expansum is a major postharvest pathogen of pome fruits, causing blue mold rot and leading to patulin contamination. Cyclic(l-anthraniloyl-l-proline) (cAntP) was identified from Lacticaseibacillus paracasei ZX1231 in our previous study. Here, we evaluated the inhibitory effect of cAntP against P. expansum, including an MIC of 1.25 mg/mL, colony growth inhibition, spore germination delay, and conidiation reduction. The antifungal mechanism of cAntP was clarified to be related to the disruption of cell membrane integrity, the leakage of intracellular components, the occurrence of activated unfolded protein response (UPR) and ER stress, and the accumulation of intracellular ROS and lipid peroxidation. Furthermore, cAntP treatment significantly reduced blue mold decay and patulin production in postharvest apple. With the nontoxicity verified by nematode Caenorhabditis elegans N2, cAntP itself is promising to be used as a fruit preservative, and its producer L. paracasei ZX1231 is a candidate to be used as a microbial antagonist in biocontrol.