Itaconic acid production in Aspergillus niger

• Main Author: van der Straat, Laura
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Wageningen University 2018
• Subjects: Life Science; Antarc*; Antarctica
• Online Access: https://research.wur.nl/en/publications/itaconic-acid-production-in-aspergillus-niger; https://doi.org/10.18174/460173

Itaconic acid (2-methylidenebutanedioic acid) is an important building block chemical that can be produced from sugars via chemical or biological conversions. Itaconic acid can be processed into a polymer, which can subsequently be used to replace the petroleum-based polyacrylic acids. Itaconic acid is naturally produced by Aspergillus terreus, certain Ustilago and Candida species and Pseudozyma antarctica. Also in mammalian cells itaconic acid is found during macrophage activation. Aspergillus niger is a filamentous fungus that is the current host of choice for the production of citric acid on an industrial scale, whereas A. terreus is the main natural producer of itaconic acid. The biosynthesis of itaconic acid is very similar to the biosynthesis of citric acid in A. niger. Citric acid concentrations of 200 g/L are nowadays obtainable with A. niger. Theoretically, this allows itaconic acid concentrations of over 135 g/L to be obtained with A. niger, which is higher that the concentrations currently obtained with A. terreus (80 g/L). However, in A. niger, cis-aconitate decarboxylase (CadA), the key enzyme for itaconic acid biosynthesis, is missing. Expression of A. terreus CadA in A. niger results in the production of a low itaconic acid concentration (0.05 g/L). The itaconic acid concentration was increased by the expression of a putative mitochondrial transporter (MttA) and a putative plasmamembrane transporter (MfsA). Expression of the MttA transporter in an itaconic acid producing A. niger strain resulted in a twenty-fold increase in itaconic acid secretion. Expression of the A. terreus itaconic acid cluster consisting of the cadA gene, the mttA gene and the mfsA gene resulted in A. niger strains that produce over twenty five-fold higher levels of itaconic acid and show a twenty-fold increase in yield compared to a strain expressing only CadA. To further increase itaconic acid production a modified 6-phosphofructo-1-kinase, pfkA, was expressed in a citrate producing A. niger strain in combination with ...