Biofumigant potential and inhibition mechanism of Trichoderma asperelloides SKRU-01 volatile organic compounds for controlling aflatoxigenic Aspergillus parasiticus and Aspergillus flavus in stored peanuts

Microbial volatile organic compounds (VOCs) have emerged as promising alternatives to synthetic fungicides for managing stored grain. In this study, the inhibitory effects of Trichoderma asperelloides SKRU-01 VOCs on hyphal growth and spore germination of Aspergillus parasiticus TISTR 3276 and A. flavus PSRDC-4 were investigated. The results demonstrated significant suppression of hyphal growth and spore germination in both strains by SKRU-01 VOCs. By using solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS), the SKRU-01 VOCs were identified to contain 23 compounds, with acetophenone being predominant (14.41%). Antifungal experiments revealed that acetophenone, at a minimum inhibitory concentration (MIC) of 1.0 μL/mL (solid media assay) or 1.0 μL/L (vapor phase assay), completely inhibited the growth of both strains. Moreover, the application of SKRU-01 VOCs effectively reduced mold density and aflatoxin B1 (AFB1) production in peanuts and also exhibited superior efficacy compared to acetophenone at a 1/2 MIC concentration. Acetophenone exhibited inhibitory effects on both fungal strains through multiple mechanisms of action. This included its ability to inhibit ergosterol biosynthesis, reduce the aflatoxin inducer methylglyoxal, impair antioxidant defense enzymes, and disrupt non-enzymatic defense molecules. Overall, this research highlights the biofumigant potential of SKRU-01 VOCs in stored grain management and provides novel insights into their antifungal mechanism against A. parasiticus and A. flavus. Furthermore, these findings contribute to the development of sustainable strategies for grain preservation and underscore the broader applications of microbial VOCs in agricultural and food safety practices.