Effect of oxylipins on ochratoxin A production by Aspergillus ochraceus in soybean culture medium

Abstract:

[Background] Ochratoxin A (OTA) is a secondary metabolite of fungi such as Aspergillus spp. and Penicillium spp., which poses a serious threat to agricultural products and food safety. Oxygenated hydroxy octadecadienoic acid (HODEs) is considered the Quorum sensing signal molecules to regulate the growth and development of Aspergillus and the production of secondary metabolites. [Objective] This experiment mainly studied the effect of HODEs on OTA production of Aspergillus ochraceus AS3.4412, and detected different changes of spore density, medium type and OTA yield under the action of endogenous and exogenous HODEs. [Methods] The culture of AS3.4412 was carried out in PDB, soybean and black bean medium respectively. The content of OTA was determined by high performance liquid chromatography-fluorescence detection and the content of oxylipins was determined by high performance liquid chromatography-mass spectrometry. The relationship among population density of A. Ochraceus, Oxylipins and OTA was found according to the variation rule of the experimental results. [Results] The results showed that 9(S)-HODE/13(S)-HODE and OTA production in low density A. ochraceus (103 spores/mL) culture was higher than high density (106 spores/mL). Exogenous addition of 9(S)-HODE promoted OTA synthesis, and 13(S)-HODE inhibitd OTA synthesis. A. ochraceus infects black beans with higher antioxidant capacity and produces more OTA. [Conclusion] The results showed that population density and HODEs could affects the OTA production of A. ochraceus. It is speculated that 9(S)-HODE and 13(S)-HODE are quorum sensing signals of A. ochraceus, and they have the opposite effect in regulating OTA synthesis.