Antimicrobial mechanism and biocontrol effect of Bacillus cereus XZ30-2 on Aspergillus niger

Aspergillus niger is a major mold-causing spoilage in cereals, fruits and vegetables. Controlling of mold in stored grains is essential for safety of food. Currently, application of microorganisms to control A. niger is a safer and more effective method. In this study, strain XZ30-2 against A. niger was isolated and identified as Bacillus cereus according to morphological and biochemical characteristics as well as 16 Svedberg ribosomal ribonucleic acid (16S rRNA) gene sequence analysis. The investigation of action mechanism showed XZ30-2 culture filtrate caused the mycelia inflated or contract, increasing the membrane permeability, leading to the intracellular leakage and nucleic acids release, disrupting the proton pump, decreasing the ergosterol content, inducing the membrane lipid peroxidation and reactive oxygen species (ROS) accumulation in A. niger. Moreover, B. cereus XZ30-2 culture filtrate could produce hydrolases and lipopeptides, including iturin, surfactin and fengycin. This work also evaluated the control effect of XZ30-2 on A. niger in wheat grains, and indicated that 40 μL/g of culture filtrate significantly controlled the infection of A. niger. Therefore, B. cereus XZ30-2 can be developed as a biological agent for controlling A. niger in stored grains.