Effect of Volatile Compounds from Bacillus subtilis PW2 against Aspergillus ochraceus

Abstract

The composition of antifungal volatile compounds (VC) produced by Bacillus subtilis PW2 was identified by solid phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS). Then, the identified single components were selected to determine their inhibitory effect against Aspergillus ochraceus by plate buckling method, and the effect and mechanism of the most active VC on the growth and toxicity of A. ochraceu. The results showed that 41 components including esters, aldehydes, alkanes, alcohols, ketones, acids and olefins were identified in the VC produced by PW2. Among these compounds, 2-ethyl hexanol (2-EH) had the strongest inhibitory activity against A. ochraceus. Direct contact with 2-EH at a dose of 1 562.5 μL/L completely inhibited the growth of A. ochraceus and reduced the content of ochratoxin A (OTA) by 23.67%. 2-EH vapor at doses of 112 and 281 μL/L completely inhibited and killed A. ochraceus, respectively. The spores of A. ochraceus treated with 2-EH appeared wrinkled, sunken and shriveled, and the integrity of the cell membrane was destroyed. Furthermore, the mycelial ergosterol content decreased by 42.68%–65.40%, and nucleic acid and protein leaked out of the cells after this treatment. This study shows that 2-EH can inhibit and kill A. ochraceus by destroying its cell membrane, which provides a theoretical basis for the application of 2-EH in the prevention of food mildew.

Keywords

• bacillus subtilis; volatile compounds; 2-ethyl hexanol; aspergillus ochraceus; ochratoxin a; inhibition