Escherichia coli strains which over-produce l-threonine and processes for the production of l-threonine by fermentation

Abstract From the Canadian patent

The present invention relates to a process for producing an Escherichia coli strain , producing between about 95 and about 120 g/L of L-threonine by about 48 hours of , growth in culture. The process comprises inserting into the chromosome of an E. coli , at least one threonine operon operably linked to a promoter non-native to the threonine operon to produce a parent strain wherein the threonine operon , comprises genes and coding enzymes necessary for threonine biosynthesis; and performing at , least two cycles of mutagenesis on the parent strain followed by screening , the , mutagenized cells to identify E. coli which produce between about 95 and about 120 , g/L of L-threonine by …