CZ256991A3 - process for preparing l-threonine by fermentation using the production strain escherichia coli 472 t-23 - Google Patents

Description

Technology .....

The present invention relates to a fermentation method using a mutated strain of Escherichia coli 472 T-23

BACKGROUND OF THE INVENTION

Escherichia coli 472 T-23 mutant with amplified gene - for homoserindehydrogenase, with penicillin resistance a_____ with partial isoleucine dependence, see. US 4,278,765, accumulated in inoculum inoculated media grown in media with 0.2% yeast extract as the source of isoleucine when cultured in fermentation tanks up to 40 g / l threonine at a conversion of 33% based on sucrose. The presence of suitable sources of isoleucine in the medium, in addition to its effect on production, has also resulted in an increase in the genetic stability of plasmid-containing production strains prepared by genetic engineering methods. Chem. Chem., 54, 619 (1990).

SUMMARY OF THE INVENTION

The present invention is based on the fermentation preparation of L-threonine using a production strain of Escherichia coli 472 T-23 in a medium containing isoleucine at a concentration of 0.3 to 1.0 g / l, preferably 0.5 to 0.7 g / l. 1.

By maintaining the optimal isoleucine concentration during the cultivation of the threonine producer on the scale of the operational tanks by applying appropriate combinations of sources of isoleucine, such as cern-steep, molasses, peptone, present in the media in amounts corresponding to 0.3 to 1 mg / L, 40 hours of cultivation up to 73 g / L at a conversion of 38% to sadharose.

The following exemplary embodiment illustrates the method of the invention but does not limit it.

DETAILED DESCRIPTION OF THE INVENTION.

The fermentation itself was carried out in a 50 µm process fermentation tank at a constant temperature of 37 ° C and pressure, with vigorous stirring and aeration. For the inoculation of a 25 m @ 2 production medium containing carbon sources such as sucrose and molasses, nitrogen from ammonium sulfate, a complex source of isoleucine such as corn steep, molasses and peptone in amounts determined based on the isoleucine content of its sources which allow achieving an optimal isoleucine concentration, i. 0.3 to 1 mg / l.

This was achieved by adding 90% corn-steep and 10%.

<------- molasses and soy peptone, then supplying a phosphate source _______________ such as potassium dihydrogen phosphate, sodium chloride, trace elements, antifoams such as soybean oil and penicillin G. 250 ml of suspension obtained by cultivation in a laboratory fermentation tank for 24 h under conditions identical to those applied in the production stage. The process was controlled by the dosing of the alkaline saaharose solution respectively. a solution containing a mixture of sucrose and molasses based on an analytical determination of sucrose so that the concentration of sucrose does not fall below 5 g / l. During fermentation, the pH was maintained at 7.0 by dosing with 25% ammonia solution. In this way, production of 73 g / l of threonine was achieved in 40 h of cultivation with a conversion of 38% sucrose. Threonine was isolated from the culture fluid both as a technical product and as a crystalline preparation.

INDUSTRIAL APPLICABILITY Threonine prepared by the process of the invention can be used both for the production of compound feeds and at higher purity for the manufacture of medicaments.

Claims (2)

PATENT CLAIMS A method for the fermentative preparation of L-threonine using a production strain of Escharichia coli 472 T-23, characterized in that the cultivation is carried out in a medium containing isoleucine at a concentration of 0.3 to 1 mg / l. 2. The method of claim 1 wherein the concentration of isoleucine in the medium is 0.5 to 0.7 mg / L.