Unlocking the potentials of cyanobacterial photosynthesis for directly converting carbon dioxide into glucose

Glucose is the most abundant monosaccharide, serving as an essential energy source for cells in all domains of life and as an important feedstock for biorefinery industry. The current glucose supply is dominated by a plant-biomass-sugar route, while direct conversion of carbon dioxide into glucose through photosynthesis has not been well studied. Here, we demonstrated that the potential of Synechococcus elongatus PCC 7942 for photosynthetic glucose production can be unlocked by preventing native glucokinase activity. Knocking out two glucokinase genes caused a specific genomic mutation, leading to effective secretion of glucose from the previously underestimated sucrose metabolism pathway. Without heterologous catalysis or transportation genes, glucokinase deficiency and spontaneous genomic mutation enabled a glucose secretion of 1.5 g/L, which was further increased to 5 g/L through metabolic and cultivation engineering. Our study underliness the cyanobacterial metabolism plasticities and lays the foundation for the industrial applications of this novel glucose production technology.