Analysis of gluconate metabolism for pyruvate production in engineered Escherichia coli based on genome-wide transcriptomes

For pyruvate-producing strains, intracellular reduced nicotinamide adenine dinucleotide (NADH) accumulation is the main reason for the glycolysis inhibition. Comparing with glucose, using sodium gluconate as carbon source brought a decrease in NADH production and an increase in pyruvate production in engineered strain YP211. In order to explore the metabolic advantages of gluconate, genome-wide transcriptome analysis was employed to compare the metabolic differences between the two carbon sources. The results showed that the transcription of the genes gntU, gntK, and gntT responsible for transport and phosphorylation of gluconate, and genes edd and eda belonging to the Entner-Doudoroff (ED) pathway, was significantly enhanced. This suggested that the shortest route for the synthesis of pyruvate from gluconate was activated, and the synthesis of NADH was halved. Besides, the transcription of genes glpABCDTKF related to the glycerol metabolism was significantly enhanced, which might be because glycerol metabolism pathways were activated in the absence of glucose. These results provided valuable information for the further design of metabolic pathways in the construction of pyruvate-producing strains.

Significance and impact of the study: Comparing with glucose, using sodium gluconate as carbon source brought a decrease in nicotinamide adenine dinucleotide and an increase in pyruvate production in engineered strain YP211. From the genome-wide transcriptome analysis, the Entner-Doudoroff pathway was activated strongly in gluconate metabolism, which innovatively provided a shorter and more effective pathway for pyruvate production.