Metabolic responses of Aspergillus niger ES4 to ethanol stress

Abstract

Aspergillus niger ES4 is a fungus isolated from the top wall of an ethanol tank of the PTT public company limited. Because normally, microorganism cannot tolerate high amount of ethanol, the growth of A. niger ES4 on the ethanol tank indicates the special properties of this fungal strain in response to ethanol. This research was therefore aimed at studying the effects of ethanol on the metabolites production of A. niger ES4 by using both untargeted and targeted metabolomics. When A. niger ES4 cultures were grown in minimal media containing 4% of ethanol for 3 days, A. niger ES4 responded to ethanol stress by changing contents of metabolite production, when compared with no ethanol conditions. For untargeted metabolomics, we found the final ion lists from the negative ion modes with 18 and 53 ions with increasing levels and 35 and 69 ions with decreasing levels in ethanol-treated samples in media and mycelium, respectively. For the positive ion modes, we found 177 and 474 ions with increasing levels and 18 and 90 ions with decreasing levels in ethanol-treated samples in media and mycelium, respectively. For targeted metabolomics in mycelium, two lipids, diacylglycerol and triacylglycerol, were statistically-significantly elevated when compared with no ethanol conditions, while other lipids, such as fatty acid, phosphatidic acid, phosphatidylethanolamine, phosphatidylserine, phosphatidyl-glycerol, and phosphatidylinositol, remained unaltered. These metabolites might be related to the tolerance of A. niger ES4, potentially benefiting ethanol-related industries or leading to discovery of the novel methods to eliminate mold.