Production of threonine byBrevibacterium flavum containing threonine biosynthesis genes fromEscherichia coli

Genes of the threonine operon ofEscherichia coli were used for the construction of aBrevibacterium flavum strain excreting threonine. Using the shuttle vector pCEM300 and a newly constructed shuttle vector pEC71 (7.1 kb, Km^r/Nm^r), various plasmids carryingE. coli thr genes were prepared. Mutants resistant to the threonine analog 2-amino-3-hydroxyvaleric acid (AHV) were isolated after the ethyl methanesulfonate treatment ofB. flavum carrying these recombinant plasmids. A mutant ofB. flavum CCM 351 carrying the cloned genesthrA andthrB accumulated 12 g/L of threonine after 48 h of cultivation.