This thesis investigates the optimized production of itaconic acid using Aspergillus terreus, focusing on the impact of manganese (Mn²⁺) on yield. Itaconic acid, a sustainable alternative to petrochemical products, is used in plastics, resins, and biofuels. The study examines key fermentation parameters, including pH, temperature, and aeration, to maximize yield while controlling Dry Cell Weight (DCW). Findings reveal that manganese concentration significantly affects production, providing strategies to enhance industrial-scale yields. The research also highlights the potential impact of manganese leaching from bioreactors in industrial settings.