Fed‐batch production of <scp>l</scp>‐tryptophan from glycerol using recombinant <i>Escherichia coli</i>

Abstract

Abstract l ‐tryptophan is an essential amino acid of high industrial interest that is routinely produced by microbial processes from glucose as carbon source. Glycerol is an alternative substrate providing a variety of economic and metabolic advantages. Process performance of the recombinant l ‐tryptophan producer Escherichia coli NT367 was studied in controlled fed‐batch processes. The chromosome of the recombinant l ‐tryptophan producer was equipped with additional genes coding for enzymes of the aromatic amino acids biosynthetic pathway and l ‐serine biosynthesis, including genes for feedback‐resistant enzyme variants ( trpE fbr , aroFBL , and serA fbr ) , deletions of enzymatic steps for the degradation of precursors or the product l ‐tryptophan ( sdaB and tnaA ), and alterations in the regulation of l ‐tryptophan metabolism (deletion of trpL and trpR ). The impact of glycerol supply rates as well as the application of a multicopy plasmid (pF112‐ aro FBL ‐ kan) were investigated in fully controlled stirred‐tank bioreactors on a 15 L scale. The combination of E. coli NT367 carrying pF112‐ aro FBL ‐ kan and an appropriate biomass‐specific glycerol supply‐rate resulted in the highest final product concentration of 12.5 g L −1 l ‐tryptophan with the lowest concentrations of other aromatic amino acids. Fed‐batch production of l ‐tryptophan from glycerol was shown for the first time with recombinant E. coli .