Itaconic acid is an important industrial building block and is produced by the filamentous fungi Aspergillus terreus. To make the optimization process more efficient, a scale-down from shake flasks to microtiter plates was performed. This resulted in comparable product formations, and 87.7 g/L itaconic acid was formed after 10 days of cultivation in the microtiter plate. The components of the minimal medium were varied independently for a media optimization. This resulted in an increase of the itaconic acid concentration by a variation of the KH2PO4 and CuSO4 concentrations. The cultivation with a higher KH2PO4 concentration in a 400-mL bioreactor showed an increase in the maximum productivity of 1.88 g/L/h, which was an increase of 74 % in comparison to the reference. Neither the phosphate concentration nor the nitrogen sources were limited at the start of the product formation. This showed that a limitation of these substances is not necessary for the itaconic acid formation.