Effect of different metabolic pathways on itaconic acid production in engineered Corynebacterium glutamicum

Abstract

Itaconic acid (IA), a C5-dicarboxylic acid, is a potential bio-based building block for the polymer industry. There are three pathways for IA production from natural IA producers; however, most of the engineered strains were used for IA production by heterologous expression of cis-aconitate decarboxylase gene (cadA) from Aspergillus terreus. In this study, IA was produced by an engineered Corynebacterium glutamicum ATCC 13032 expressing two different types of genes from two distinct pathways. The first involves the mammalian immunoresponsive gene1 (Irg1) derived from Mus musculus. The second (termed here the trans-pathway) involves two genes from the natural IA producer Ustilago maydis which are aconitate-delta-isomerase (Adi1) and trans-aconitate decarboxylase (Tad1) genes. The constructed strains developing the two distinct IA production pathways: C. glutamicum ATCC 13032 pCH-Irg1_opt and C. glutamicum ATCC 13032 pCH-Tad1_optadi1_opt were used for production of IA from different carbon sources. The results reflect the possibility for IA production from C. glutamicum expressing the trans-pathway (Adi1/Tad1 genes) and cis-pathway (Irg1 gene) other than the well-known cis-pathway that depends mainly on cadA gene from A. terreus. The developed strain expressing trans-pathway from U. maydis; however, proved to be better at IA production with high titers of 12.25, 11.34, and 11.02 g/L, and a molar yield of 0.22, 0.42, and 0.43 mol/mol from glucose, maltose, and sucrose, respectively, via fed-batch fermentation. The present study suggests that trans-pathway is better than cis-pathway for IA production in engineered C. glutamicum.

Keywords: Cis-pathway; Corynebacterium glutamicum; Fed-batch fermentation; Immunoresponsive gene; Itaconic acid; Trans-pathway.