Elementary Mode Analysis for the Rational Design of Efficient Succinate Conversion from Glycerol byEscherichia coli

Zhen Chen,Hongjuan Liu,Dehua Liu,Jianan Zhang

doi:10.1155/2010/518743

Abstract

By integrating the restriction of oxygen and redox sensing/regulatory system, elementary mode analysis was used to predict the metabolic potential of glycerol for succinate production by E. coli under either anaerobic or aerobic conditions. It was found that although the theoretical maximum succinate yields under both anaerobic and aerobic conditions are 1.0 mol/mol glycerol, the aerobic condition was considered to be more favorable for succinate production. Although increase of the oxygen concentration would reduce the succinate yield, the calculation suggests that controlling the molar fraction of oxygen to be under 0.65 mol/mol would be beneficial for increasing the succinate productivity. Based on the elementary mode analysis, the rational genetic modification strategies for efficient succinate production under aerobic and anaerobic conditions were obtained, respectively. Overexpressing the phosphoenolpyruvate carboxylase or heterogonous pyruvate carboxylase is considered to be the most efficient strategy to increase the succinate yield.

Highlights

Glycerol has become an abundant and inexpensive carbon source due to its generation as an inevitable byproduct of biodiesel production
The results suggested that aerobic condition was more favorable for biomass formation and the most effective way for biomass formation was through the tricarboxylic acid (TCA) cycle
The potentials of using glycerol for succinate production in E. coli under the anaerobic and aerobic conditions were compared by using elementary mode analysis in this work

Summary

Introduction

Glycerol has become an abundant and inexpensive carbon source due to its generation as an inevitable byproduct of biodiesel production. Much effort has been paid for the development of processes to convert crude glycerol into higher-value products to maximize the full economic potential of biodiesel process. Several recent studies tried to utilize glycerol as a carbon source for the transformation of other valued products such as ethanol [5] and amino acids [6]. Despite few attempts in the past, no industrially competitive organisms can effectively produce succinate from glycerol so far. In the light of the new powerful tools of metabolic engineering, the quest for targeted development of strains that can effectively utilize glycerol for succinate production is strongly revived. E. coli is one of the most promising organisms since it can directly utilize glycerol and it has been traditionally developed for succinate production [8,9,10]

Methods

Results

Conclusion