Fig. 2

a Schematic overview of heterologous d-glucaric acid (GA) synthesis pathways in engineered Escherichia coli starting from glucose [18]. Red text indicates key substances in the synthesis pathway of GA. Black and bold text represent heterologous enzymes involved in the production of GA. b Sucrose is used as an alternative substrate for GA synthesis in vivo and some genes are knocked out to increase GA production. Some genes related to the consumption of GA synthesis intermediates, such as G6P, GlcA, and GA, have been knocked out. A red cross indicates that enzymes in the relevant metabolic pathway have been eliminated [25]. c Dynamic regulation of genes to increase GA production. The means of sending G6P to glycolysis in pink arrow is to dynamically knock-down Pfk-I, whose expression is controlled by a quorum-sensing system [45]. A degradation tag is fused with Pfk-I and it rapidly loses activity in the presence of SspB. The black “TF” indicates transcriptional activator protein EsaR170V. In the pathway of conversion of G6P to GA, the expression of MIOX has been dynamically controlled by a biosensor-based promoter regulated by the MI-specific sensor IpsA. The red “TF” indicates transcriptional repressor IpsA. CscA invertase, CscB sucrose permease, CscK d-fructokinase, GudD glucarate dehydratase, Ino1 myo-inositol-1-phosphate synthase, MIOX myo-inositol oxygenase, PGI phosphoglucose isomerase, Pfk-I phosphofructokinase-1, PPP pentose phosphate pathway, PTS phosphotransferase, SuhB inositol-1-monophosphatase, Udh uronate dehydrogenase, UxaC uronate isomerase, Zwf glucose-6-phosphate dehydrogenase