Metabolite profiling and adaptation mechanisms of Aspergillus cristatus under pH stress

LC-MS and multivariate analyses showed that <i>A. cristatus</i>'s growth at different pH involved significantly different metabolites. In particular, comparing pH 4.0 vs pH 6.0, pH 6.0 vs pH 8.0 and pH 4.0 vs pH 8.0 revealed a total of 317, 171 and 404 significantly different substances, respectively. Finally, as the pH changed from 4.0 to 6.0 to 8.0, eight changes in the patterns of differential substances were identified. At low pH, <i>A. cristatus</i> accumulated large amounts of energy substances (e.g., adenosine), active antioxidants (e.g., glutathione) and osmo-protective substances (e.g., raffinose). In contrast, at high pH, large amounts of phosphatidylcholine (PC), lysophosphatidyl ethanolamine (LPE), lysophosphatidyl choline (LPC), lysophosphatidyl serine (LPS) related to biofilms were synthesized, alongside antioxidants (e.g., formononetin) and acidic substances. The aforementioned results indicate that <i>A. cristatus</i> adapts to changes in pH by adjusting their metabolite synthesis. Therefore, under unsuitable pH environments, <i>A. cristatus</i> synthesizes specific sets of metabolites that play key roles to cope with the stress.