L-Cysteine hydrochloride inhibits Aspergillus flavus growth and AFB₁ synthesis by disrupting cell structure and antioxidant system balance

Aflatoxin B1 (AFB₁) is the most potent known naturally occurring carcinogen and pose an immense threat to food safety and human health. L-Cysteine hydrochloride (L-CH) is a food additive often used as a fruit and vegetable preservative and also to approved bread consistency. In this study, we investigated the effects and mechanisms of L-CH as an antimicrobial on the growth of Aspergillus flavus (A. flavus) and AFB₁ biosynthesis. L-CH significantly inhibited A. flavus mycelial growth, affected mycelial morphology and AFB₁ synthesis. Furthermore, L-CH induced glutathione (GSH) synthesis which scavenged intracellular reactive oxygen species (ROS). RNA-Seq indicated that L-CH inhibited hyphal branching, and spore and sclerotia formation by controlling cell wall and spore development-related genes. Activation of the GSH metabolic pathway eliminated intracellular ROS, leading to hyphal dwarfing. L-CH treatment downregulated most of the Aflatoxin (AF) cluster genes and aflS, aflR, AFLA_091090 transcription factors. This study provides new insights into the molecular mechanism of L-CH control of A. flavus and AFB₁ foundation. We believe that L-CH could be used as a food additive to control AFB₁ in foods and also in the environment.