Mitsubishi Petrochemical Company Limited

Mitsubishi Chemical Corporation

Keiko Kohama

Hideaki Yukawa

Yasurou Kurusu

Makiko Fukushima

Masato Terasawa

Terukazu Nara

Mitsunobu Shimazu

Kazuhisa Hatakeyama

Yukie Satoo

Miki Kobayashi

The present invention relates to a DNA fragment which contains a gene responsible for the function of autonomous replication of plasmid in a Coryneform bacterium, said gene being obtained from plasmid pBY503 held in Brevibacterium stationis, and in which at least one point mutation capable of increasing the copy number of plasmid exists on said gene region. By using a Coryneform transformed with the vector constructed using said DNA fragment and an industrially useful gene such as aspartase gene or tryptophan synthase gene, production of the useful product occurs with higher efficiency than conventional methods.

Coryneform bacteria DNA fragment containing a gene responsible for the

A DNA fragment derived from plasmid pBY503 obtained from Brevibacterium stationis IF012144, said DNA fragment containing a gene which encodes for the function of maintaining a plasmid, capable of replicating and proliferating at least in a Coryneform bacteria of the genus Brevibacterium, stably in said bacteria; and a vector DNA capable of replicating and proliferating in a Coryneform bacteria into which the above DNA fragment is introduced.

DNA fragment containing gene which encodes the function of stabilizing

A method for producing L-threonine, which comprises subjecting at least L- or DL-aspartic acid or a salt thereof to enzymatic reaction according to the reaction system not accompanied with growth of microorganism cells in an aqueous solution in the presence of a microorganism and collecting L-threonine formed, wherein the microorganism is a biotin-requiring microorganism for the growth belonging to coryneform bacterium; a plasmid comprising a DNA fragment containing at least a gene encoding biosynthesis of threonine which can be expressed within a biotin-requiring microorganism cell for the growth belonging to coryneform bacterium and a DNA fragment containing a gene encoding autonomous replication within coryneform bacterium cell; and a biotin-requiring microorganism for the growth belonging to coryneform bacterium which has been transformed with the plasmid described above, both of which are employed in the present method. According to the present invention, L-threonine can be produced with good yield, and further since production management becomes extremely easy without requiring cumbersome operation such as sterilization of the medium, etc. as in the fermentation method, L-threonine can be produced inexpensively in industry.

Method for producing L-threonine, and plasmid and microorganism employed

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Ibaraki, Japan

Keiko Kohama