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

Abstract

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 the biorefinery industry. The plant-biomass-sugar route dominates the current glucose supply, while the direct conversion of carbon dioxide into glucose through photosynthesis is not well studied. Here, we show 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 causes intracellular accumulation of glucose and promotes the formation of a spontaneous mutation in the genome, which eventually leads to glucose secretion. Without heterologous catalysis or transportation genes, glucokinase deficiency and spontaneous genomic mutation lead to a glucose secretion of 1.5 g/L, which is further increased to 5 g/L through metabolic and cultivation engineering. These findings underline the cyanobacterial metabolism plasticities and demonstrate their applications for supporting the direct photosynthetic production of glucose.

Engineering Cyanobacterial Cell Factories for Photosynthetic Production of Fructose

“…In contrast, overexpression of glk did not increase but significantly decreased the fructose titers (to less than 400 mg/L). The possible reason for this phenomenon might be that glucokinase was also able to catalyze fructose as a nonspecific substrate and supplement the lost fructokinase activities in JS22 . Among the recombinant strains, JS41 (JS22- spp 6803) had the highest fructose production (1.9 g/L after 12 days of cultivation), further confirming the importance of enhancing the sucrose synthesis pathway to produce fructose; thus, this strain was selected for subsequent evaluations and optimizations.…”

Combinatorial optimization of gene expression through recombinase-mediated promoter and terminator shuffling in yeast

“…However, the successful implementation of heterologous pathways and perturbation of native microbial metabolism often requires extensive optimization to ensure economically viable production titers. Metabolic engineering allows rewiring of cellular metabolism to increase product titers by enhancing precursor supply 3 , 4 , tackling co-factor limitations 5 – 7 , interrupting competitive pathways 8 , 9 , preventing buildup of toxic intermediates 10 and improving heterologous pathway flux 11 . Over the past years, several tools and strategies have been developed to facilitate yield optimization, including chassis strain improvement 12 – 14 , directed mutagenesis 15 – 17 , synthetic compartmentalization 18 , 19 and pathway gene expression optimization 20 .…”

Advances in Label-Free Glucose Detection Using Self-Assembled Nanoparticles and Surface-Enhanced Raman Spectroscopy

“…Glucose, a pivotal component in biological processes, plays a critical role wherein its concentration and structural variations are integral to the functionality of these processes. 1 Typically, glucose maintains a dynamic equilibrium within bodily fluids, with normal fasting blood glucose levels ranging between 3.9 and 6.1 mmol/L. 2 Disorders in glucose metabolism can precipitate diabetes, subsequently leading to severe complications such as diabetic cardiomyopathy, nephropathy, retinopathy, and neuropathy, positioning it as a leading cause of mortality globally.…”