Factors Affecting Production of Itaconic Acid from Mixed Sugars by Aspergillus terreus

Itaconic acid (IA; a building block platform chemical) is currently produced industrially from glucose by fermentation with Aspergillus terreus. In order to expand the use of IA, its production cost must be lowered. Lignocellulosic biomass has the potential to serve as low-cost source of sugars for IA production. It was found that the fungus cannot produce IA from dilute acid pretreated and enzymatically saccharified wheat straw hydrolysate even at 100-fold dilution. The effects of typical compounds (acetic acid, furfural, HMF and Mn²⁺, enzymes, CaSO₄), culture conditions (initial pH, temperature, aeration), and medium components (KH₂PO₄, NH₄NO₃, CaCl₂·2H₂O, FeCl₃·6H₂O) on growth and IA production by A. terreus NRRL 1972 using mixed sugar substrate containing glucose, xylose, and arabinose (4:3:1, 80 g L^-1) mimicking the wheat straw hydrolysate were investigated. Acetic acid, furfural, Mn²⁺, and enzymes were strong inhibitors to both growth and IA production from mixed sugars. Optimum culture conditions (pH 3.1, 33 °C, 200 rpm) and medium components (0.8 g KH₂PO₄, 3 g NH₄NO₃, 2.0 g CaCl₂·2H₂O, 0.83-3.33 mg FeCl₃·6H₂O per L) as well as tolerable levels of inhibitors (0.4 g acetic acid, < 0.1 g furfural, 100 mg HMF, < 5.0 ppb Mn²⁺, 24 mg CaSO₄ per L) for mixed sugar utilization were established. The results will be highly useful for developing a bioprocess technology for IA production from lignocellulosic feedstocks.