The ornithine-urea cycle involves fumaric acid biosynthesis in var. , a green and eco-friendly process for fumaric acid production.

The current petroleum chemical methods for fumaric acid production can cause heavy pollution and global warming. In this study, the engineered strains of var. were found to be suitable for green fumaric acid producer. Removal and complementation of the relevant genes showed only the ornithine-urea cycle (OUC) was involved in high level fumarate biosynthesis which was controlled by the Ca signaling pathway. Removal of both the gene encoding glucose oxidase and the gene encoding the polyketide synthase for 3,5-dihydroxydecanoic acid biosynthesis and overexpression of the gene encoding pyruvate carboxylase made the strain e-PYC produce 88.1 ± 4.3 g/L of fumarate at flask level and 93.9 ± 0.8 g/L of fumarate during the fed-batch fermentation. As a yeast-like fungal strain, it was very easy to cultivate var. DH177 and their mutants in the bioreactor and to edit its genomic DNAs to enhance fumarate production. It was found that 2 mol of CO could be fixed during a maximal theoretical yield of 2 mol of fumarate per mole of glucose consumed in the OUC. Therefore, the OUC-mediated fumarate biosynthesis pathway in var. was a green and eco-friendly process for the global sustainable development and carbon neutrality.