Method for producing l-threonine by fermentation of bacteria with altered aconitase regulatory elements

Abstract

The invention provides a method for producing L-threonine through fermentation. The method comprises the steps of transforming the wild type regulatory element of an acnA gene on bacterial chromosome, so that the expression quantity of the aconitase A is lowered, but not disappear; and producing L-threonine through fermentation of the transformed bacteria. In addition, the invention also provides methods and applications derived from the method for producing L-threonine through fermentation, and bacteria used in the methods and applications.

Description

technical field [0001] The present invention belongs to the field of amino acid fermentation, and in particular, the present invention relates to a method for fermentative production of l-threonine and its derivation method and application, and bacteria that can be used in these methods and applications. Background technique [0002] Production of l-threonine by fermentation of l-threonine-producing bacteria (eg, Escherichia coli of the genus Escherichia and rod-shaped bacteria of the genus Corynebacterium) has been industrially applied. These bacteria can be bacteria isolated from nature, bacteria obtained through mutagenesis or genetic engineering, or both. In the current literature reports, the attention through genetic engineering is mainly focused on AKIII, thrR In terms of isogenes (see Chinese patents 94102007 and 99121353, etc.), there is no focus on aconitase (eg, aconitase A) and its coding gene for the production of L-threonine. [0003] Aconitase is an enzyme i...

AI Technical Summary

Problems solved by technology

It is known that in Escherichia, acnA The gene (its nucleotide sequence is shown in SEQ ID No: 1) encodes aconitase A, but it may be because its metabolism is too far away from the final l-threonine product, and there are too many and complicated intermediate metabolic branches, while It has not attracted people's attention in the fermentation of l-threonine

[0004] After long-term research and practice, especially with some luck, the inventor accidentally found that the transformation of the regulatory elements of the acnA gene can help Increase the production of l-threonine; however, the prior art either introduces beneficial enzyme genes with increased expression and / or enzymatic activity by increasing copies and / or site-directed mutations, or knocks out unfavorable genes to make them enzymatically active and / or the expression level disappears, but differently, the inventors found that the regulatory elements of the acnA gene cannot be simply improved or knocked out, especially after knocking out acnA gene makes the growth of bacteria difficult and difficult for practical application, so a new method targeting the regulatory element of the acnA gene was developed to increase the production of l-threonine, and the The method does not conflict with the chromosomal modification sites of a large number of high-yield L-threonine-producing bacteria that have been transformed, and the improved effect can be superimposed, so that it can be used in the production of L-threonine by bacterial fermentation in practice