2-09: Alternative carbon sources for Escherichia coli cultivation

Bach cultivation of  Escherichia coli with low concentration of glucose, a known and largely used carbon source, results in high yield (0.6 g DCW g glucose), however, by increasing glucose concentration, there is a redirection of carbon flux to acetate production with consequent reduction of biomass yield (0.35 g DCW g glucose). The cultivation of this microorganism at medium composition capable to minimize acetate formation could result in higher biomass yield and awake an important industrial appeal. In this study we evaluated the behavior of the Escherichia coli when cultivated in four different carbon sources (xylose, sorbitol, glucose and glycerol) in order to identify a potential source with low cost and which allow this microorganism achieve high cell density. Glycerol and sorbitol appear as important carbon sources that can be metabolized with low acetate accumulation, even in culture with high substrate concentration, maintaining specific growth rate around of 0.6 h^-1 and 0.5 h^-1, respectively. Cultivation in high concentration of xylose as carbon source achieved high yields (0.41 DCW g xylose) and specific growth rate around 0.6 h^-1. Xylose is an important sugar that can be obtained from hydrolyse of hemicellulose that is present in sugarcane bagasse and could be used by E. coli as substrate to produce add value products such as recombinant hydrolases and intermediate chemicals.