Factors improving L-threonine production by a three L-threonine biosynthetic genes-amplified recombinant strain of Brevibacterium lactofermentum.

When a Brevibacterium lactofermentum L-threonine producer that accumulated L-lysine as well, was transformed with a recombinant plasmid carrying the indigenous hom, thrB, and thrC genes, delayed growth and plasmid instability were observed. Addition of organic nutrients, vitamins (thiamine.HCl and d-biotin), and NaCl under the optimal culture conditions solved these problems and further increased threonine production in a small jar fermentor.