Inhibitory roles of Bacillus velezensis YE-1 isolated from lichens in Baiyin city, Gansu province against Aspergillus flavus

Abstract Aspergillus flavus has evoked worldwide attention owing to its serious threat to public health, but how to safely, efficiently, and economically reduce A. flavus contamination remains a great challenge. Here, a Bacillus strain capable of inhibiting A. flavus was isolated from lichens. The antifungal assay showed that Bacillus velezensis YE-1 could inhibit the growth of A. flavus. Scanning and transmission electron microscopy revealed that B. velezensis YE-1 exposure severely deformed the spore and mycelial structure and morphology of A. flavus. Furthermore, the biochemical studies revealed a significant alternation in ergosterol content, mitochondrial membrane potential, nuclear DNA, and aflatoxin synthesis gene in A. flavus exposed to B. velezensis YE-1. In addition, the inhibitory activity of isolated B. velezensis YE-1 was mainly present in the cell-free supernatant, confirming that the heat-resistant non-protein substances produced by B. velezensis YE-1 exerted an antagonistic role on A. flavus. Finally, on corn and peanut kernels, B. velezensis YE-1 can also remarkably improve the disease severity by A. flavus. Therefore, our results showed that B. velezensis YE-1 could be a very promising biocontrol agent for A. flavus and subsequent contamination of food/feed commodities.