Application of Escherichia coli Coculture System for n-Butanol Production
n-Butanol is a substituted fuel of poteintial and can be blended with gasoline at any concentrations for use. It has been historically produced by Clostridium species in a bioprocess known as the ABE fermentation. However, this fermentation process is difficult to operate efficiently due to a complicated regulation circuit. Escherichia coli is known as a biotechnology workhorse and is promising for n-butanol production. In this work, a new production platform of n-butanol in E. coli was presented. This production system consists of two strains, a butyrate-producing strain and a butyrate-conversion strain. The latter strain was developed by recruitment of endogenous atoDA and Clostridium adhE2. M9 mineral salt plus yeast extract (M9Y) was used and this strain produced 6.2 g/L n-butanol from supplemented butyrate. The molar conversion yield accounts for 92%. The butyrate-producing strain was equipped with a heterologous pathway leading to butyrate. The production of n-butanol was then developed by co-culturing these two strains. As a result, 5.5 g/L n-butanol from glucose was obtained in the coculture system in M9Y medium at 24 h. The production yield on glucose accounts for 69% of the theoretical yield. Overall, the result indicates that this new production platform of n-butanol is promising and may open a new avenue of bio-butanol production in E. coli.