Mitsubishi Petrochemical Company Limited

Research Association for Utilization of Light Oil

Makiko Fukushima

Hideaki Yukawa

Yasurou Kurusu

Masato Terasawa

Keiko Kohama

Terukazu Nara

Hisashi Yamagata

Yukie Satoo

Mitsunobu Shimazu

Miki Kobayashi

A process for cultivating a microorganism transformed with a recombinant plasmid at least containing (a) a DNA fragment containing a promoter and a regulator gene tnaC located downstream of the promoter in a tryptophanase operon (tna), and (b) a DNA fragment containing a desired structural gene which can be expressed by the promoter, which comprises cultivating the transformed microorganism in a culture medium while adding glucose as a carbon source continuously or intermittently so that the concentration of glucose is maintained within the range of 0.01 to 0.3%, and thereby allowing the desired structural gene to be expressed in the microorganism.

Cultivation of transformed microorganisms

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

Growing community of inventors

Ami, Japan

Makiko Fukushima