2017 Metabolic Engineering Summit
Green Biosynthesis of Chemicals and Biofuels
Green Biosynthesis of Chemicals and Biofuels
Metabolic engineering was applied to provide the efficient production of chemicals and biofuels. i) Co-fermentation of C5 and C6 sugars as well as CO2 by engineering yeasts to simultaneously and efficiently convert maltose, xylose and glucose as well as in-situ produced CO2 into ethanol by coupling the CO2-fixation pathway into the fundamental xylose pathway. The introduction of CO2 as electron acceptor for NADH oxidation not only increases ethanol yield from xylose, but also enhances ethanol productivity. Expression of Form-I Rubisco further enhanced xylose metabolic flux and improved xylose consumption rate. The results present an innovative strategy where using CO2 drives and redistributes the central pathways of sugars to desirable products and demonstrate a possible breakthrough in increased fermentation yield of sugars. ii) Cofactor engineering strategies have been applied successfully for enhancing the production of S-adenosylmethionine (SAM), 1-butanol and 1,3-propanediol (1,3-PDO). As a result, SAM titer produced by the E. coli SSP-1 was increased to
5.3 mg/L, 13 times of that with the control, the NADH/NAD+ ratio in the engineered 1-butanol strain was increased by 78 135% and the 1,3-PDO titer produced by K. pneumoniae was improved to 86 g/L. iii) The theoretical yield of three production pathways of adipic acid by flux balance analysis (FBA) using genome-scale metabolic network of Corynebacterium glutamicum was calculated. The pathway of highest theoretical yield, with lysine as an intermediate, is chosen as the most promising production pathway of adipic acid and its maximum theoretical yield is 87.4%. According to the above, relationship between cell growth and theoretical yield of adipic acid is analyzed there are inversely related between theoretical yield and growth rate. In addition, it is shown by cofactor flux analysis that the pathway needs a lot of NADH. Thus, the modification of the strains based on the simulation results could be guided.
Metabolic engineering was applied to provide the efficient production of chemicals and biofuels. i) Co-fermentation of C5 and C6 sugars as well as CO2 by engineering yeasts to simultaneously and efficiently convert maltose, xylose and glucose as well as in-situ produced CO2 into ethanol by coupling the CO2-fixation pathway into the fundamental xylose pathway. The introduction of CO2 as electron acceptor for NADH oxidation not only increases ethanol yield from xylose, but also enhances ethanol productivity. Expression of Form-I Rubisco further enhanced xylose metabolic flux and improved xylose consumption rate. The results present an innovative strategy where using CO2 drives and redistributes the central pathways of sugars to desirable products and demonstrate a possible breakthrough in increased fermentation yield of sugars. ii) Cofactor engineering strategies have been applied successfully for enhancing the production of S-adenosylmethionine (SAM), 1-butanol and 1,3-propanediol (1,3-PDO). As a result, SAM titer produced by the E. coli SSP-1 was increased to
5.3 mg/L, 13 times of that with the control, the NADH/NAD+ ratio in the engineered 1-butanol strain was increased by 78 135% and the 1,3-PDO titer produced by K. pneumoniae was improved to 86 g/L. iii) The theoretical yield of three production pathways of adipic acid by flux balance analysis (FBA) using genome-scale metabolic network of Corynebacterium glutamicum was calculated. The pathway of highest theoretical yield, with lysine as an intermediate, is chosen as the most promising production pathway of adipic acid and its maximum theoretical yield is 87.4%. According to the above, relationship between cell growth and theoretical yield of adipic acid is analyzed there are inversely related between theoretical yield and growth rate. In addition, it is shown by cofactor flux analysis that the pathway needs a lot of NADH. Thus, the modification of the strains based on the simulation results could be guided.