Culture conditions for improvement of L-threonine production using a genetically self-cloned L-threonine hyperproducing strain of Escherichia coli K-12.
We had constructed an L-threonine-hyperproducing strain of E. coli K-12 by recombinant DNA techniques. In this paper, culture conditions for the practical production of L-threonine were investigated using this strain. Cultivation temperature, concentration of required amino acids, and dissolved oxygen greatly influenced the yield of L-threonine. High production of L-threonine was obtained at a high level of dissolved oxygen for the recombinant strain, but not for the parent. This improved production was accompanied by a high copy number of recombinant plasmids and high activity of aspartokinase. Initial addition of L-threonine together with required amino acids greatly reduced the net production of L-threonine. To remove the reductive effect, methods for the addition of the required amino acids were tested. Lowering the required amino acids at a later stage of cultivation seemed to be effective to avoid the reductive effect of the accumulated L-threonine. By using the optimal conditions, the highest level of L-threonine production, 65 g/l, 48% yield, was achieved.
Shimizu
E
E
Central Research Laboratories of Ajinomoto Co., Inc., Kawasaki, Japan.
Oosumi
T
T
Heima
H
H
Tanaka
T
T
Kurashige
J
J
Enei
H
H
Miwa
K
K
Nakamori
S
S
D000596:Amino Acids / Q000494:pharmacology; D003001:Cloning, Molecular; D003470:Culture Media; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D010100:Oxygen / Q000494:pharmacology; D010957:Plasmids; D013912:Threonine / Q000096:biosynthesis*
D000596:Amino Acids; D003470:Culture Media; D013912:Threonine; D010100:Oxygen