MFA for improved productivity of 3HB in recombinant E.coli

Computer modeling has gained increasin attention as a quick method to investigate the effect of genetic changes on the metabolic networks of well-known organisms. This study has focused on the use of genome scale metabolic modelin of Escherichia coli metabolism to find ways of improving 3-hydroxybutyric acid (3HB) productivity. Standard flyx balance and flux variability analysis has been uswed, as well as thermodynamics-based metabolix flux analysis. The models led to a number of suggestions on how to improve the production. Knockouts in AF1000 pTrcT3Rx were constructed from these predictions and tested for the effect on 3HB yield. The knockouts did not improve the yield of product but they allowed some insight to the limiting factors of 3HB sythesis. Based on this information, further suggestions were made on how to improve 3HB production. To increase yield and productivity of 3HB, the growth rate of E. coli has to be limited. This can be done either through phosphorous or nitrogen limitation, or through an elevated pH. Since the production pathway is likely NADPH dependent, the glycolysis has to be steered towards the pentose phosphate pathway or the Entner-Doudoroff pathway for supply of the correct redox cofactor. This can be achieved by overexpression or knockouts of the correct genes. The use of lignocellulostic hydrolysates could potentially be a favorable substrate for an organism with modified glycolysis. In addition, such a substrate would open up possibilities for a cheaper and potentially greener process