| Summary: | 碩士 === 國立中興大學 === 化學工程學系所 === 102 === The microbial conversion for bio-based chemical productions is one of the alternative sources of energy. If the development of the system which could recycle carbon dioxide before it is emitted during the fermentation process. While the CO2 emission is lowered, the benefit is that the yield of fermentation products can be increased by using the carbon in the carbon dioxide. In previous study, Rubisco-based engineered E. coli, containing heterologous Rubisco and PrkA, produced only 0.621 mol of CO2 per consumption with pentoses, achieves 38% of theoretical CO2 reduction. Besides, our parallel study demonstrates that Rubisco-based engineered E. coli can recycle evolved CO2 with hexoses by enhancing the function of the non-oxidative pentose phosphate pathway (NOPP pathway). To further control the carbon flow during the recycling of CO2, glycolysis and pentose phosphate pathway (PP pathway) have been destroyed by disrupting zwf gene. Therefore, the carbon flux through the NOPP pathway would be increased and then that is converted into the Rubisco-based engineered pathway to recycling more CO2. Beside, focus on the effect between Rubisco and host cell, E. coli BL21 (DE3), is another point of this study.
The results shows that the M9 medium contained 20 g/L glucose as a sole carbon which in anaerobic batch culture, while E. coli BL21 (DE3) containing mutation of zwf genes (designated as MZ) and harboring PrkA and Rubisco grow normally similar to wild-type E. coli BL21 (DE3). It exhibited 54% decreased in Total CO2/PEtOH+PAcetate (mol/mol) fraction compared to the control E. coli strain containing only PrkA and Rubisco. However, Rubisco in E. coli would make response to some exclusively gluconeogenic genes due to the CsrA regulation. CsrA regulates gluconeogenic genes showed up-regulation responses, and improve PEP synthesis rate was associated with the increase of carbon dioxide evolution, which PEP is the intermediate of glycolysis. Pentose and PEP could be impact the biosynthesis of amino acids and aromatic compounds. Therefore, sugar consumption rate increase for energy storage and aromatic compounds during strain harboring Rubisco. In a few words, the performance of the destroyed the OPP pathway coupled with recombinant E. coli harboring PrkA and Rubisco, which is efficient and essential. The interaction of heterologous Rubisco with the intact metabolism of E. coli is profound and interesting. More discussion will be addressed later.
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