Escherichia Coli Strains which Over-Produce L-Threonine and Processes for the Production of L-Threonine by Fermentation

An E. coli strain producing between about 95 and about 150 g/L, of L-threonine by about 48 hours of growth in culture produced by a process comprising:

• (a) inserting into the chromosome of an E. coli at least one threonine operon operably linked to a non-native promoter to produce a parent strain;
• and
• (b) performing at least one cycle of mutagenesis on the parent strain, followed by screening the mutagenized cells to identify E. coli which produce between about 95 and about 150 g/L, of L-threonine by about 48 hours of growth in culture.