Abstract
BackgroundAs the greenhouse effect becomes more serious and carbon dioxide emissions continue rise, the application prospects of carbon sequestration or carbon-saving pathways increase. Previously, we constructed an EP-bifido pathway in Escherichia coli by combining Embden-Meyerhof-Parnas pathway, pentose phosphate pathway and “bifid shunt” for high acetyl-CoA production. There is much room for improvement in the EP-bifido pathway, including in production of target compounds such as poly(hydroxybutyrate) (PHB).ResultTo optimize the EP-bifido pathway and obtain higher PHB yields, we knocked out the specific phosphoenolpyruvate phosphate transferase system (PTS) component II Cglc, encoded by ptsG. This severely inhibited the growth and sugar consumption of the bacterial cells. Subsequently, we used multiple automated genome engineering (MAGE) to optimize the ribosome binding site (RBS) sequences of galP (galactose: H (+) symporter) and glk (glucokinase gene bank: NC_017262.1), encoding galactose permease and glucokinase, respectively. Growth and glucose uptake were partially restored in the bacteria. Finally, we introduced the glf (UDP-galactopyranose) from Zymomonas mobilis mutase sugar transport vector into the host strain genome.ConclusionAfter optimizing RBS of galP, the resulting strain L-6 obtained a PHB yield of 71.9% (mol/mol) and a 76 wt% PHB content using glucose as the carbon source. Then when glf was integrated into the genome strain L-6, the resulting strain M-6 reached a 5.81 g/L PHB titer and 85.1 wt% PHB content.
Highlights
In 2018, global carbon dioxide emissions increased 1.7% over the previous year, hitting a record high of 33.143 billion tons
Inhibiting phosphate transferase system (PTS) to Reduce PEP Consumption In E. coli, glucose is transported through the PTS system
This system is involved in PEP-dependent sugar transport and its activity has an important impact on carbon flux redistribution in the PEP and pyruvate nodes (Gosset, 2005)
Summary
In 2018, global carbon dioxide emissions increased 1.7% over the previous year, hitting a record high of 33.143 billion tons. Bio-manufacturing, which uses food crops as raw materials, has wide application prospects. Many carbon dioxide fixation pathways have been exploited using the six carbon fixation pathways discovered in nature (Gong et al, 2016). Complex reaction steps and enzyme requirements limit the broad application of these carbon sequestration pathways (Erb et al, 2007; Schwander et al, 2016). As the greenhouse effect becomes more serious and carbon dioxide emissions continue rise, the application prospects of carbon sequestration or carbonsaving pathways increase. There is much room for improvement in the EP-bifido pathway, including in production of target compounds such as poly(hydroxybutyrate) (PHB)
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