Evaluating the Potential of Co-supplementation of Zinc and Ferrous Iron Ion for Itaconic Acid Fermentation of Aspergillus terreus

Abstract

Zinc (Zn) and ferrous iron (Fe) are the essential micronutrients for the growth of microorganisms. Nonetheless, whether they affect the fermentation of Aspergillus terreus or not remains poorly understood. This study assessed the effect of co-supplementation of zinc and ferrous iron ion on itaconic acid production for A. terreus fermenting pure glucose and xylose. In single factor assays, with mycelium growth and sugar consumption improved, itaconic acid concentration was increased by 63.87% at 2 days and 29.07% at 4 days for 0.25 g/L Zn (II) and 60.90% and 50.69% for 0.40 g/L Fe (II). The highest itaconic acid productivity and yield were separately 0.17 ± 0.01 g/L·h and 0.54 ± 0.01 g/g at 8 h for 0.25 g/L Zn (II) and 0.17 ± 0.00 g/L·h and 0.55 ± 0.01 g/g for 0.40 g/L (II). Co-supplementation of the optimized concentration of Zn (II) and Fe (II) brought about the increase of 60.56% and 71.37% for itaconic acid accumulation, and thus indicated that itaconic acid fermentation required the appropriate concentration of zinc and ferrous iron ion. Furthermore, through transcriptomic sequencing, the co-supplementation of zinc and ferrous iron ion contributed to 249 differentially expressed genes (DEGs) especially with the improved gene transcriptional for sugar transporter (Glut), transketolase (Tkt), mitochondrial tricarboxylate transporter (MttA), and major facilitator superfamily protein (MfsA) in biosynthetic pathway of itaconic acid, and thus would be responsible for the improved itaconic acid fermentability for A. terreus. This work would establish the improvement tactics for itaconic acid biosynthesis through co-supplementing zinc and ferrous iron ion in fermentation system and also provide synthetic biology tools for genetic modification of A. terreus to efficiently produce itaconic acid.

Keywords: Aspergillus terreus; Ferrous iron; Itaconic acid; Zinc.