The host (Aspergillus niger CBS513.88 ΔkusA) and the mpkA gene knockout strain (Aspergillus niger CBS513.88 ΔkusA ΔmpkA) were inoculated into the DPY liquid medium and placed in a shaker at 30°C, 250 rpm for 2 d. After inoculation, the hypha was collected and analyzed by LC-MS\MS.