Increasing The Yield Of Muconic Acid By CO₂ Fixation

Environmental and energy issues are two important issues that humanity now cares about.The burning of fossil energy releases a large amount of greenhouse gases,which has a serious impact on the environment.The released CO2 can be converted into fuel or chemicals through a CO2 fixation route to reduce greenhouse gas emissions.The viscous acid is a precursor for the synthesis of adipic acid,and adipic acid can be obtained by hydrogenation.It has great applications in the manufacture of nylon66,food acidulants,pharmaceuticals,lubricants and plasticizers.The traditional methods of producing mucic acid are chemical synthesis methods,which have adverse effects on the environment.In this context,biosynthesis alleviates environmental pollution problems.This article describes the production of mucic acid in E.coli and increases the yield of mucic acid by CO2 fixation.In this experiment,RuBisCO and PRK from Ralstonia eutropha H16 strain were selected,which are key enzymes for immobilizing CO2.In order to determine the activity of the two enzymes and to determine the feasibility of the CO2 fixation pathway,an in vitro multi-enzyme reaction system was designed.After the feasible method,the CO2 fixation pathway was constructed in E.coli to improve the production of musk acid.First,the two carbon sources were used to produce mucic acid,namely glycerol and glucose.The yield of mucic acid was not increased in E.coli constructed with CO2 immobilization pathway;then zwf(6-phosphate glucose dehydrogenase)was knocked out to improve the EMP pathway.The carbon source destroyed the path of producing viscous acid by Escherichia coli.The results showed that the viscous acid could not be produced.The fermentation medium,ie,the whole glycerol,was used to produce the viscous acid.The yield of the original strain reached 2.37 g/L,and the CO2 fixation was constructed.The yield of the strain reached 1.4 g/L;Finally,E.coli endogenous RPE(phosphoribose epimerase)was overexpressed to increase the substrate required for the CO2 fixation pathway,and the yield was increased to 1.9 g/L compared to 1.4 g/L.In this experiment,the production of mucic acid was linked to CO2 fixation.Although the yield of mucic acid was not improved,the heterologous CO2 fixation pathway was expressed in E.coli and the CO2 fixation effect could be improved based on its activity expression.Providing a basis for the future CO2 fixation research.