Exploring the biocontrol performance of an unconventional yeast (Geotrichum candidum XG1) against Aspergillus flavus in corn (Zea mays L.) and its underlying mechanisms and safety

Corn is highly susceptible to pathogen invasion, such as Aspergillus flavus , leading to aflatoxin contamination and posing a significant threat to food safety. Yeasts are widely applied in the food industry, and the use of yeasts for pathogen control as an alternative to physical and chemical methods has gained increasing attention. Previous studies have investigated the aflatoxin-degrading capability of Geotrichum candidum XG1 (an unconventional yeast), but its antifungal activity and application potential have not been explored. In this study, the antifungal activity of G. candidum XG1 was evaluated both in vitro and in vivo , and its impact on corn quality was investigated. The mechanisms and safety of the yeast were also further examined. The results indicated that G. candidum XG1 significantly inhibited A. flavus , reducing the fungus and aflatoxin contamination by over 90% on corn. A 75-day storage experiment assessing changes in corn color, starch, protein, fat, and fatty acid values revealed that G. candidum XG1 had minimal impact on corn quality. Compared to the control group (infected with A. flavus ), it significantly reduced the quality deterioration caused by A. flavus invasion. Gas chromatography-mass spectrometry (GC-MS) analysis identified phenylethyl alcohol as a key compound involved in the antifungal activity of the yeast. Phenylethyl alcohol inhibited A. flavus by affecting its cell morphology, energy metabolism, and defense systems. Safety evaluations, including whole-genome sequencing and animal trials, confirmed the safety of the strain. This study provides valuable insights into the application of antagonists like G. candidum XG1 for controlling pathogen in corn.