Figure 25). This suppression of acid synthesis under salt stress has been reported previously in filamentous fungi, where increasing salinity redirects metabolism toward biomass preservation rather than organic acid secretion, thereby diminishing leaching and neutralization capacity (Prusky & Yakoby, 2003; Thangavelu, Tang, Ryan, & Valix, 2006). This suggests that alkalinity may enhance organic acid production and neutralization capacity, while high salinity likely triggers a stress response that prioritizes biomass maintenance over acid secretion. This metabolic shift is consistent with activation of the high‑osmolarity glycerol pathway, which responds to osmotic stress and has been previously reported to play a role in mediating these metabolic changes under hyperosmotic conditions, leading to reductions in pyruvate and tricarboxylic acid cycle intermediates (Kim, Oh, & Sung, 2016). Figure 23- A. niger (A) and P. oxalicum (B) tolerance under different alkalinity conditions. The red dashed line indicates a tolerance index of 0.5. Asterisks (*) represent statistically significant changes. Figure 24- A. niger (A) and P. oxalicum (B) tolerance under different salinity conditions. The red dashed line indicates a tolerance index of 0.5. Asterisks (*) represent statistically significant changes. A) B) A) B)
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