Differential effects of ammonium and nitrate on lignocellulose degradation and nitrogen metabolism of Irpex lacteus in wheat straw

White rot fungi, such as Irpex lacteus , offer significant potential for lignocellulose degradation in sustainable biofuel and animal feed production, but optimizing nitrogen sources to balance fungal growth, lignin degradation, and protein synthesis remains a critical challenge. This study investigated the effects of ammonium chloride (NH₄Cl) and sodium nitrate (NaNO₃) on the solid-state fermentation of I. lacteus in wheat straw. While all treatments resulted in significant degradation of acid-insoluble lignin (AIL) compared to the raw material, only NH₄Cl supplementation increased fungal biomass. After 28 days of fermentation, NaNO₃ treatment achieved an absolute AIL loss ranging from 44.5 % to 61.4 %. Critically, the NH₄Cl group exhibited a significantly higher final AIL content than both the control and NaNO₃ groups ( P  < 0.05). Furthermore, NaNO₃ enhanced glucose and xylose yields from the residual wheat straw by up to 19.8 % and 46 %, respectively, compared to the control. Transcriptomic analysis revealed that the NaNO₃ group had higher expression of genes related to nitrogen uptake and cellulose/hemicellulose degradation than the control. Compared to NH₄Cl, NaNO₃ also mitigated the downregulation of genes encoding manganese peroxidase and several cytochrome P450s. These findings suggest that NaNO₃ promotes I. lacteus metabolism by coordinating lignocellulose degradation with efficient nitrogen assimilation.