PROCESS FOR THE FERMENTATIVE PREPARATION OF L-AMINO ACIDS WITH AMPLIFICATION OF THE GND GENE

Description

[0001] The invention relates to a process for the fermentative preparation of L-amino acids, in particular L-lysine, L-threonine, L-isoleucine and L-tryptophan, using coryneform bacteria in which at least the gnd gene is amplified.

Prior art

[0002] L-Amino acids are used in animal nutrition, in human medicine and in the pharmaceuticals industry.

[0003] It is known that amino acids are prepared by fermentation from strains of coryneform bacteria, in particular Corynebacterium glutamicum. Because of their great importance, work is constantly being undertaken to improve the preparation processes. Improvements to the process can relate to fermentation measures, such as e.g. stirring and supply of oxygen, or the composition of the nutrient media, such as e.g. the sugar concentration during the fermentation, or the working up to the product form by e.g. ion exchange chromatography, or the intrinsic output properties of the microorganism itself.

[0004] Methods of mutagenesis, selection and mutant selection are used to improve the output properties of these microorganisms. Strains which are resistant to antimetabolites, such as e.g. the threonine analogue α-amino-β-hydroxyvaleric acid (AHV), or are auxotrophic for metabolites of regulatory importance and produce L-amino acids such as e.g. threonine are obtained in this manner.

[0005] Methods of the recombinant DNA technique have also been employed for some years for improving the strain of Corynebacterium glutamicum strains which produce L-amino acids.

[0006] WO 01/07626 describes the production of L-amino acids, comprising culturing an altered bacterial cell (I), having an increased amount of NADPH (reduced nicotinamide adenine dinucleotide phosphate) or a decreased amount of 6-phosphoglucose isomerase (Pgi) enzymatic activity, as compared to an unaltered bacterial cell, where yields of L-amino acid from (I) are greater than yields from unaltered bacterial cell.

[0007] In EP-A-733712 the productivity of the production of substances such as L-amino-acids, antibiotics, vitamins, growth factors, and physiologically active substances by microbial fermentation is improved by improving the production of reduced nicotinamide adenine dinucleotide phosphate (NADPH) in the microbial cells. This may be carried out by transforming the cells to improve the enzyme activity of nicotinamide nucleotide transhydrogenase (NNT) in the microbial cells, to improve the expression of the NNT gene, and improve the copy number of the NNT gene in the cells. Suitable microorganisms include strains of Escherichia coli, Corynebacterium and Brevibacterium . USE - The method may be used for more efficient large-scale production of substances for use in the pharmaceutical, food, animal feedstuff and chemical industries, esp. L-amino acids, antibiotics, vitamins, growth factors and other physiologically active substances

Object of the invention

[0008] The inventors had the object of providing improved processes for the fermentative preparation of L-amino acids with coryneform bacteria.

Description of the invention

[0009] L-Amino acids are used in human medicine and in the pharmaceuticals industry, in the foodstuffs industry and especially in animal nutrition. There is therefore a general interest in providing new improved processes for the preparation of amino acids.

[0010] The invention provides a process for the fermentative preparation of L-amino acids, in particular L-lysine, L-threonine, L-isoleucine and L-tryptophan, using coryneform bacteria in which the nucleotide sequence which codes for the enzyme 6-phosphogluconate dehydrogenase (EC number 1.1.1.44) (gnd gene) is amplified, in particular over-expressed.

[0011] Specifically, the invention provides a process for the preparation of L-amino acids by fermentation of coryneform bacteria which comprises carrying out the following steps:

a) fermentation of the desired L-amino acid-producing bacteria in which at least the gnd gene is amplified and at least the poxB gene is attenuated,

b) concentration of the L-amino acid in the medium or in the cells of the bacteria and

c) isolation of the L-amino acid produced.

[0012] The strains employed preferably already produce L-amino acids before amplification of the gnd gene.

[0013] Preferred embodiments are to be found in the claims.

[0014] The term "amplification" in this connection describes the increase in the intracellular activity of one or more enzymes in a microorganism which are coded by the corresponding DNA, for example by increasing the number of copies of the gene or genes, using a potent promoter or using a gene which codes for a corresponding enzyme having a high activity, and optionally combining these measures.

[0015] The microorganisms which the present invention provides can prepare L-amino acids from glucose, sucrose, lactose, fructose, maltose, molasses, starch, cellulose or from glycerol and ethanol. They are representatives of coryneform bacteria, in particular of the genus Corynebacterium. Of the genus Corynebacterium, there may be mentioned in particular the species Corynebacterium glutamicum, which is known among experts for its ability to produce L-amino acids.

[0016] Suitable strains of the genus Corynebacterium, in particular of the species Corynebacterium glutamicum, are, for example, the known wild-type strains
   Corynebacterium glutamicum ATCC13032
   Corynebacterium acetoglutamicum ATCC15806
   Corynebacterium acetoacidophilum ATCC13870
   Corynebacterium thermoaminogenes FERM BP-1539
   Brevibacterium flavum ATCC14067
   Brevibacterium lactofermentum ATCC13869
   Brevibacterium divaricatum ATCC14020
and L-amino acid-producing mutants prepared therefrom,
such as, for example, the L-threonine-producing strains
   Corynebacterium glutamicum ATCC21649
   Brevibacterium flavum BB69
   Brevibacterium flavum DSM5399
   Brevibacterium lactofermentum FERM-BP 269
   Brevibacterium lactofermentum TBB-10
and such as, for example, the L-isoleucine-producing strains
   Corynebacterium glutamicum ATCC 14309
   Corynebacterium glutamicum ATCC 14310
   Corynebacterium glutamicum ATCC 14311
   Corynebacterium glutamicum ATCC 15168
   Corynebacterium ammoniagenes ATCC 6871
and such as, for example, the L-tryptophan-producing strains
   Corynebacterium glutamicum ATCC21850
   Corynebacterium glutamicum KY9218(pKW9901)
and such as, for example, the L-lysine-producing strains
   Corynebacterium glutamicum FERM-P 1709
   Brevibacterium flavum FERM-P 1708
   Brevibacterium lactofermentum FERM-P 1712
   Corynebacterium glutamicum FERM-P 6463
   Corynebacterium glutamicum FERM-P 6464
   Corynebacterium glutamicum DSM5715
   Corynebacterium glutamicum DM58-1
   Corynebacterium glutamicum DSM12866.

[0017] It has been found that coryneform bacteria produce L-amino acids, in particular L-lysine, L-threonine, L-isoleucine and L-tryptophan, in an improved manner after over-expression of the gnd gene which codes for 6-phosphogluconate dehydrogenase (EC number 1.1.1.44) and attenuation of the poxB gene which codes for the pyruvate oxidase.

[0018] The gnd gene codes for the enzyme 6-phosphogluconate dehydrogenase , which catalyses the oxidative decarboxylation of 6-phosphogluconic acid to ribulose 5-phosphate. The nucleotide sequence of the gnd gene is disclosed in JP-A-9-224662. The gnd gene described in the text reference mentioned is used according to the invention for the first time. Alleles of the gnd gene which result from the degeneracy of the genetic code or due to sense mutations of neutral function can furthermore be used.

[0019] To achieve an amplification (e.g. over-expression), the number of copies of the corresponding genes is increased, or the promoter and regulation region or the ribosome binding site upstream of the structural gene is mutated. Expression cassettes which are incorporated upstream of the structural gene act in the same way. By inducible promoters, it is additionally possible to increase the expression in the course of fermentative L-amino acid formation. The expression is likewise improved by measures to prolong the life of the m-RNA. Furthermore, the enzyme activity is also increased by preventing the degradation of the enzyme protein. The genes or gene constructs are either present here in plasmids with a varying number of copies, or are integrated and amplified in the chromosome. Alternatively, an over-expression of the genes in question can furthermore be achieved by changing the composition of the media and the culture procedure.

[0020] Instructions in this context can be found by the expert, inter alia, in Martin et al. (Bio/Technology 5, 137-146 (1987)), in Guerrero et al. (Gene 138, 35-41 (1994)), Tsuchiya and Morinaga (Bio/Technology 6, 428-430 (1988)), in Eikmanns et al. (Gene 102, 93-98 (1991)), in European Patent Specification EPS 0 472 869, in US Patent 4,601,893, in Schwarzer and Pühler (Bio/Technology 9, 84-87 (1991), in Reinscheid et al. (Applied and Environmental Microbiology 60, 126-132 (1994)), in LaBarre et al. (Journal of Bacteriology 175, 1001-1007 (1993)), in Patent Application WO 96/15246, in Malumbres et al. (Gene 134, 15-24 (1993)), in Japanese Laid-Open Specification JP-A-10-229891, in Jensen and Hammer (Biotechnology and Bioengineering 58, 191-195 (1998)) and in known textbooks of genetics and molecular biology.

[0021] By way of example, 6-phosphogluconate dehydrogenase was over-expressed with the aid of a plasmid. The E. coli - C. glutamicum shuttle vector pEC-T18mob2 shown in Figure 1 was used for this. After incorporation of the gnd gene into the EcoRI cleavage site of pEC-T18mob2, the plasmid pECgnd shown in Figure 2 was formed.

[0022] Other plasmid vectors which are capable of replication in C. glutamicum, such as e.g. pEKExl (Eikmanns et al., Gene 102:93-98 (1991)) or pZ8-1 (EP-B- 0 375 889), can be used in the same way.

[0023] In addition, it may be advantageous for the production of L-amino acids to amplify one or more enzymes of the particular biosynthesis pathway, of glycolysis, of anaplerosis, of the pentose phosphate pathway or of amino acid export, in addition to amplification of the gnd gene which codes for 6-phosphogluconate dehydrogenase and the attenuation of the pox B gene which codes for the pyruvate oxidase.

[0024] Thus, for example, in particular for the preparation of L-threonine, one or more genes chosen from the group consisting of

• the hom gene which codes for homoserine dehydrogenase (Peoples et al., Molecular Microbiology 2, 63-72 (1988)) or the hom^dr allele which codes for a "feed back resistant" homoserine dehydrogenase (Archer et al., Gene 107, 53-59 (1991),
• the gap gene which codes for glyceraldehyde 3-phosphate dehydrogenase (Eikmanns et al., Journal of Bacteriology 174: 6076-6086 (1992)),
• the pyc gene which codes for pyruvate carboxylase (Peters-Wendisch et al., Microbiology 144: 915-927 (1998)),
• the mqo gene which codes for malate:quinone oxidoreductase (Molenaar et al., European Journal of Biochemistry 254, 395-403 (1998)),
• the tkt gene which codes for transketolase (accession number AB023377 of the databank of European Molecular Biology Laboratories (EMBL, Heidelberg, Germany)),
• the zwf gene which codes for glucose 6-phosphate dehydrogenase (JP-A-09224661),
• the thrE gene which codes for threonine export (DE 199 41 478.5; DSM 12840),

can be amplified, in particular over-expressed, at the same time.

[0025] Thus, for example, in particular for the preparation of L-lysine, one or more genes chosen from the group consisting of

• the dapA gene which codes for dihydrodipicolinate synthase (EP-B 0 197 335),
• a lysC gene which codes for a feed back resistant aspartate kinase (Kalinowski et al. (1990), Molecular and General Genetics 224: 317-324),
• the gap gene which codes for glyceraldehyde 3-phosphate dehydrogenase (Eikmanns (1992), Journal of Bacteriology 174:6076-6086),
• the pyc gene which codes for pyruvate carboxylase (Eikmanns (1992), Journal of Bacteriology 174:6076-6086),
• the tkt gene which codes for transketolase (accession number AB023377 of the databank of European Molecular Biologies Laboratories (EMBL, Heidelberg, Germany)),
• the zwf gene which codes for glucose 6-phosphate dehydrogenase (JP-A-09224661),
• the lysE gene which codes for lysine export (DE-A-195 48 222),

can be amplified, in particular over-expressed, at the same time.

[0026] In addition to over-expression of 6-phosphogluconate dehydrogenase and attenuation of pyruvate oxidase, it may furthermore be advantageous for the production of L-amino acids to eliminate undesirable side reactions (Nakayama: "Breeding of Amino Acid Producing Micro-organisms", in: Overproduction of Microbial Products, Krumphanzl, Sikyta, Vanek. (eds.), Academic Press, London, UK, 1982).

[0027] The microorganisms prepared according to the invention can be cultured continuously or discontinuously in the batch process (batch culture) or in the fed batch (feed process) or repeated fed batch process (repetitive feed process) for the purpose of L-amino acid production. A summary of known culture methods is described in the textbook by Chmiel (Bioprozesstechnik 1. Einführung in die Bioverfahrenstechnik [Bioprocess Technology 1. Introduction to Bioprocess Technology (Gustav Fischer Verlag, Stuttgart, 1991)) or in the textbook by Storhas (Bioreaktoren und periphere Einrichtungen [Bioreactors and Peripheral Equipment] (Vieweg Verlag, Braunschweig/Wiesbaden, 1994)).

[0028] The culture medium to be used must meet the requirements of the particular microorganisms in a suitable manner. Descriptions of culture media for various microorganisms are contained in the handbook "Manual of Methods for General Bacteriology" of the American Society for Bacteriology (Washington D.C., USA, 1981). Sugars and carbohydrates, such as e.g. glucose, sucrose, lactose, fructose, maltose, molasses, starch and cellulose, oils and fats, such as e.g. soya oil, sunflower oil, groundnut oil and coconut fat, fatty acids, such as e.g. palmitic acid, stearic acid and linoleic acid, alcohols, such as e.g. glycerol and ethanol, and organic acids, such as e.g. acetic acid, can be used as the source of carbon. These substances can be used individually or as a mixture. Organic nitrogen-containing compounds, such as peptones, yeast extract, meat extract, malt extract, corn steep liquor, soya bean flour and urea, or inorganic compounds, such as ammonium sulfate, ammonium chloride, ammonium phosphate, ammonium carbonate and ammonium nitrate, can be used as the source of nitrogen. The sources of nitrogen can be used individually or as a mixture. Potassium dihydrogen phosphate or dipotassium hydrogen phosphate or the corresponding sodium-containing salts can be used as the source of phosphorus. The culture medium must furthermore comprise salts of metals, such as e.g. magnesium sulfate or iron sulfate, which are necessary for growth. Finally, essential growth substances, such as amino acids and vitamins, can be employed in addition to the above-mentioned substances. Suitable precursors can moreover be added to the culture medium. The starting substances mentioned can be added to the culture in the form of a single batch, or can be fed in during the culture in a suitable manner.

[0029] Basic compounds, such as sodium hydroxide, potassium hydroxide, ammonia, or acid compounds, such as phosphoric acid or sulfuric acid, can be employed in a suitable manner to control the pH. Antifoams, such as e.g. fatty acid polyglycol esters, can be employed to control the development of foam. Suitable substances having a selective action, e.g. antibiotics, can be added to the medium to maintain the stability of plasmids. To maintain aerobic conditions, oxygen or oxygen-containing gas mixtures, such as e.g. air, are introduced into the culture. The temperature of the culture is usually 20°C to 45°C, and preferably 25°C to 40°C. Culturing is continued until a maximum of L-amino acid has formed. This target is usually reached within 10 hours to 160 hours.

[0030] The analysis of L-amino acids can be carried out by anion exchange chromatography with subsequent ninhydrin derivatization, as described by Spackman et al. (Analytical Chemistry, 30, (1958), 1190), or it can take place by reversed phase HPLC as described by Lindroth et al. (Analytical Chemistry (1979) 51:. 1167-1174).

[0031] The following microorganism has been deposited at the Deutsche Sammlung für Mikroorganismen und Zellkulturen (DSMZ = German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany) in accordance with the Budapest Treaty:

Escherichia coli K-12 DH5α/pEC-T18mob2 as DSM 13244

[0032] The following figures are attached:

• Figure 1: Map of the plasmid pEC-T18mob2
• Figure 2: Map of the plasmid pECgnd
• Figure 3: Map of the plasmid pBGNA
• Figure 4: Map of the plasmid pCR2.1poxBint

[0033] The base pair numbers stated are approx. values obtained in the context of reproducibility.

[0034] The abbreviations used have the following meaning:

Re Figure 1:

Tet:

Resistance gene for tetracycline

oriV:

Plasmid-coded replication origin of E. coli

RP4mob:

mob region for mobilizing the plasmid

rep:

Plasmid-coded replication origin from C. glutamicum plasmid pGA1

per:

Gene for controlling the number of copies from pGA1

lacZ-alpha:

lacZα gene fragment (N-terminus) of the β-Galactosidase gene

Re Figure 2:

Tet:

Resistance gene for tetracycline

rep:

Plasmid-coded replication origin from C. glutamicum plasmid pGA1

per:

Gene for controlling the number of copies from PGA1

lacZ

Cloning relict of the lacZα gene fragment from pEC-T18mob2

gnd:

6-Phosphogluconate dehydrogenase gene

Re Figure 3:

LacP:

Promoter of the E. coli lactose operon

CMV:

Promoter of cytomegalovirus

ColE1:

Replication origin of the plasmid ColE1

TkpolyA:

Polyadenylation site

Kan r:

Kanamycin resistance gene

SV40ori:

Replication origin of Simian virus 40

gnd:

6-Phosphogluconate dehydrogenase gene

Re Figure 4:

ColE1 ori:

Replication origin of the plasmid ColE1

lacZ:

Cloning relict of the lacZα gene fragment

fl ori:

Replication origin of phage f1

KmR:

Kanamycin resistance

ApR:

Ampicillin resistance

poxBint:

internal fragment of the poxB gene

[0035] Moreover, the following abbreviations have been used:

AccI:

Cleavage site of the restriction enzyme AccI

BamHI:

Cleavage site of the restriction enzyme BamHI

EcoRI:

Cleavage site of the restriction enzyme EcoRI

HindIII:

Cleavage site of the restriction enzyme HindIII

KpnI:

Cleavage site of the restriction enzyme KpnI

PstI:

Cleavage site of the restriction enzyme PstI

PvuI:

Cleavage site of the restriction enzyme PvuI

SalI:

Cleavage site of the restriction enzyme SalI

SacI:

Cleavage site of the restriction enzyme SacI

SmaI:

Cleavage site of the restriction enzyme SmaI

SphI

Cleavage site of the restriction enzyme SphI

XbaI:

Cleavage site of the restriction enzyme XbaI

XhoI:

Cleavage site of the restriction enzyme XhoI

Examples

[0036] The following examples will further illustrate this invention. The molecular biology techniques, e.g. plasmid DNA isolation, restriction enzyme treatment, ligations, standard transformations of Escherichia coli etc. used are, (unless stated otherwise), described by Sambrook et al., (Molecular Cloning. A Laboratory Manual (1989) Cold Spring Harbour Laboratories, USA).

Example 1

Construction of a gene library of Corynebacterium glutamicum strain AS019

[0037] A DNA library of Corynebacterium glutamicum strain ASO19 (Yoshihama et al., Journal of Bacteriology 162, 591-597 (1985)) was constructed using ë Zap Express™ system, (Short et al., (1988) Nucleic Acids Research 16: 7583-7600), as described by O'Donohue (O'Donohue, M. (1997). The Cloning and Molecular Analysis of Four Common Aromatic Amino Acid Biosynthetic Genes from Corynebacterium glutamicum. Ph.D. Thesis, National University of Ireland, Galway). ë Zap Express™ kit was purchased from Stratagene (Stratagene, 11011 North Torrey Pines Rd., La Jolla, California 92037) and used according to the manufacturers instructions. AS019-DNA was digested with restriction enzyme Sau3A and ligated to BamHI treated and dephosphorylated ë Zap Express™ arms.

Example 2

Cloning and sequencing of the gnd gene

1. Construction of a gnd probe

[0038] A radiolabelled oligonucleotide, internal to the gnd gene, was used to probe the AS019 ë Zap Express™ library described above. The oligonucleotide was produced using degenerate PCR primers internal to the gnd gene. The degenerate nucleotide primers designed for the PCR amplification of gnd DNA fragments were as follows:



with R=A+G; Y=C+T; K=T+G.

[0039] The estimated size of the resulting PCR product was 252 bp approximately.

[0040] Optimal PCR conditions were determined to be as follows:

35 cycles

94°C for 1 minute

55°C for 1 minute

72°C for 30 seconds

2.5 - 3.5 mM MgCl₂

100 - 150 ng AS019 genomic DNA

[0041] Sequence analysis of the resulting PCR product confirmed the product to be an internal portion of a gnd gene. Sequence analysis was carried out using the universal forward and reverse primers, and T7 sequencing kit from Pharmacia Biotech, (St. Albans, Herts, UK). The sequence of the PCR product is shown in SEQ ID No. 1.

2. Cloning

[0042] Screening of the AS019 ë Zap Express™ library was carried out according to the ë Zap Express™ system protocol, (Stratagene, 11011 North Torrey Pines Rd., La Jolla, California 92037). Southern Blot analysis was then carried out on isolated clones. Southern transfer of DNA was as described in the Schleicher and Schuell protocols manual employing Nytran™ as membrane ("Nytran, Modified Nylon-66 Membrane Filters" (March 1987), Schleicher and Schuell, Dassel, Germany). Double stranded DNA fragments, generated using the same primers and optimal PCR conditions as described above, were radiolabelled with α-³²P-dCTP using the Multiprime™ DNA labelling kit from Amersham Life Science (Amersham Pharmacia Biotech UK Limited, Little Chalfont, Buckinghamshire, UK) according to the manufacturers instructions. Prehybridisation, hybridization and washing conditions were as described in the Schleicher and Schuell protocols manual. Autoradiography was carried out according to the procedure outlined in the handbook of Sambrook et al. using AgFa Curix RPIL film. Thus several gnd clones were identified. Plasmid DNA was isolated from one of the clones, designated pBGNA (Figure 3) and chosen for further analysis.

3. Sequencing

[0043] The Sanger Dideoxy chain termination method of Sanger et al. (Proceedings of the National Academy of Sciences USA 74, 5463-5467 (1977)) was used to sequence the cloned insert of pBGNA. The method was applied using the T7 sequencing kit and α-³⁵S-dCTP from Pharmacia Biotech (St. Albans, Herts, UK). Samples were electrophoresed for 3-8 hours on 6% polyacrylamide/urea gels in TBE buffer at a constant current of 50 mA, according to the Pharmacia cloning and sequencing instructions manual ("^T7 Sequencing™ Kit",ref.XY-010-00-19, Pharmacia Biotech, 1994). Sequence analysis was carried out using internal primers designed from the sequence known of the internal gnd PCR product (SEQ ID NO 1) allowing the entire gnd gene sequence to be deduced.

[0044] The sequences of the internal primers were as follows:

[0045] Sequence obtained was then analyzed using the DNA Strider programme, (Marck (1988), Nucleic Acids Research 16: 1829-1836), version 1.0 on an Apple Macintosh computer. This program allowed for analyses such as restriction site usage, open reading frame analysis and codon usage determination. Searches between DNA sequence obtained and those in EMBL and Genbank databases were achieved using the BLAST programme (Altschul et al., (1997), Nucleic Acids Research 25: 3389-3402). DNA and protein sequences were aligned using the Clustal V and Clustal W programs (Higgins and Sharp, 1988 Gene 73: 237-244).

[0046] The sequence thus obtained is shown in SEQ ID NO 2. The analysis of the nucleotide sequence obtained revealed an open reading frame of 1377 base pairs which was designated as gnd gene. It codes for a protein of 459 amino acids shown in SEQ ID NO 3.

Example 3

Preparation of the shuttle vector pEC-T18mob2

[0047] The E. coli - C. glutamicum shuttle vector pEC-T18mob2 was constructed according to the prior art.

[0048] The vector contains the replication region rep of the plasmid pGA1 including the replication effector per (US-A-5,175,108; Nesvera et al., Journal of Bacteriology 179, 1525-1532 (1997)), the tetracycline resistance-imparting tetA(Z) gene of the plasmid pAG1 (US-A- 5,158,891; gene library entry at the National Center for Biotechnology Information (NCBI, Bethesda, MD, USA) with accession number AF121000), the replication region oriV of the plasmid pMB1 (Sutcliffe, Cold Spring Harbor Symposium on Quantitative Biology 43, 77-90 (1979)), the lacZ gene fragment including the lac promoter and a multiple cloning site (mcs) (Norrander et al. Gene 26, 101-106 (1983)) and the mob region of the plasmid RP4 (Simon et al., (1983) Bio/Technology 1:784-791).

[0049] The vector constructed was transformed in the E. coli strain DH5α (Hanahan, In: DNA cloning. A practical approach. Vol. I. IRL-Press, Oxford, Washington DC, USA, 1985). Selection for plasmid-carrying cells was made by plating out the transformation batch on LB agar (Sambrook et al., Molecular cloning: a laboratory manual. 2^nd Ed. Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., USA, 1989), which had been supplemented with 5 mg/l tetracycline. Plasmid DNA was isolated from a transformant with the aid of the QIAprep Spin Miniprep Kit from Qiagen and checked by restriction with the restriction enzyme EcoRI and HindIII subsequent agarose gel electrophoresis (0.8%).

[0050] The plasmid was called pEC-T18mob2 and is shown in Figure 1. It is deposited in the form of the strain Escherichia coli K-12 strain DH5α/pEC-T18mob2 at the Deutsche Sammlung für Mikroorganismen und Zellkulturen (DSMZ = German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany) as DSM 13244.

Example 4

Cloning of the gnd gene into the E. coli - C. glutamicum shuttle vector pEC-T18mob2

[0051] PCR was used to amplify DNA fragments containing the entire gnd gene of C. glutamicum and flanking upstream and downstream regions using pBGNA as template. PCR reactions were carried out using oligonucleotide primers designed from SEQ ID NO 2. The primers used were:

[0052] PCR parameters were as follows:

35 cycles

95°C for 6 minutes

94°C for 1 minute

50°C for 1 minute

72°C for 45 seconds

1 mM MgCl₂

approx. 150-200ng pBGNA-DNA as template.

[0053] The PCR product obtained was cloned into the commercially available pGEM-T vector purchased from Promega Corp. (pGEM-T Easy Vector System 1, cat. no. A1360, Promega UK, Southampton) using E. coli strain JM109 (Yanisch-Perron et al. Gene, 33: 103-119 (1985)) as a host. The entire gnd gene was subsequently isolated from the pGEM T-vector on an EcoRI fragment and cloned into the lacZ EcoRI site of the E. coli - C. glutamicum shuttle vector pEC-T18mob2 (Figure 1), and designated pECgnd (Figure 2). Restriction enzyme analysis with AccI (Boehringer Mannheim GmbH, Germany) revealed the correct orientation (i. e. downstream the lac-Promotor) of the gnd gene in the lacZα gene of pEC-T18mob2.

Example 5

Preparation of amino acid producers with amplified 6-phosphogluconate dehydrogenase

[0054] Plasmid pECgnd from Example 3 was electroporated by the electroporation method of Tauch et al. (FEMS Microbiological Letters, 123:343-347 (1994)) in the strains Corynebacterium glutamicum DSM 5399 and DSM 5714. The strain DSM 5399 is a threonine producer described in EP-B-0358940. The strain DSM 5714 is a lysine producer described in EP-B-0435132. Selection of transformants was carried out by plating out the electroporation batch on LB agar (Sambrook et al., Molecular cloning: a laboratory manual. 2^nd Ed. Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., 1989), which had been supplemented with 25 mg/l kanamycin. The strains DSM5399/pECgnd and DSM5714/pECgnd were formed in this manner.

Example 6

Preparation of threonine

[0055] The C. glutamicum strain DSM5399/pECgnd obtained in Example 5 was cultured in a nutrient medium suitable for the production of threonine and the threonine content in the culture supernatant was determined.

[0056] For this, the strain was first incubated on an agar plate with the corresponding antibiotic (brain-heart agar with tetracycline (5 mg/l)) for 24 hours at 33°C. Starting from this agar plate culture, a preculture was seeded (10 ml medium in a 100 ml conical flask). Brain-heart broth (Merck, Darmstadt, Germany) was used as the medium for the preculture. Tetracycline (5 mg/l) was added to this medium. The preculture was incubated for 24 hours at 33°C at 240 rpm on a shaking machine. A main culture was seeded from this preculture such that the initial OD (660nm) of the main culture was 0.1. The medium MM-threonine was used for the main culture.

Medium MM-threonine:
CSL	5 g/l
MOPS	20 g/l
Glucose(autoclaved separately)	50g/l

Salts:
(NH4)2SO4	25 g/l
KH2PO4	0.1 g/l
MgSO4 * 7 H2O	1.0 g/l
CaCl2 * 2 H2O	10 mg/l
FeSO4 * 7 H2O	10 mg/l
MnSO4 * H2O	5.0mg/l
Biotin (sterile-filtered)	0.3 mg/l
Thiamine * HCl (sterile-filtered)	0.2 mg/l
CaCO3	25 g/l

[0057] The CSL (corn steep liquor), MOPS (morpholinopropanesulfonic acid) and the salt solution were brought to pH 7 with aqueous ammonia and autoclaved. The sterile substrate and vitamin solutions were then added, as well as the CaCO₃ autoclaved in the dry state.

[0058] Culturing is carried out in a 10 ml volume in a 100 ml conical flask with baffles. Tetracycline (5 mg/l) was added. Culturing was carried out at 33°C and 80% atmospheric humidity.

[0059] After 48 hours, the OD was determined at a measurement wavelength of 660 nm with a Biomek 1000 (Beckmann Instruments GmbH, Munich). The concentration of threonine formed was determined with an amino acid analyzer from Eppendorf-BioTronik (Hamburg, Germany) by ion exchange chromatography and post-column derivatization with ninhydrin detection.

[0060] The result of the experiment is shown in Table 1.

Table 1

Strain	OD(660)	L-Threonin g/l
DSM5399/pECgnd	11.9	1.29
DSM5399	11.8	0.33

Example 7

Preparation of lysine

[0061] The C. glutamicum strain DSM5714/pECgnd obtained in Example 5 was cultured in a nutrient medium suitable for the production of lysine and the lysine content in the culture supernatant was determined.

[0062] For this, the strain was first incubated on an agar plate with the corresponding antibiotic (brain-heart agar with tetracycline (5 mg/l)) for 24 hours at 33°C. Starting from this agar plate culture, a preculture was seeded (10 ml medium in a 100 ml conical flask). The complete medium CgIII was used as the medium for the preculture.

Medium Cg III
NaCl	2.5 g/l
Bacto-Peptone	10 g/l
Bacto-Yeast extract	10 g/l
Glucose (autoclaved separately)	2% (w/v)

[0063] The pH was brought to pH 7.4

[0064] Tetracycline (5 mg/l) was added to this medium. The preculture was incubated for 24 hours at 33°C at 240 rpm on a shaking machine. A main culture was seeded from this preculture such that the initial OD (660nm) of the main culture was 0.05. Medium MM was used for the main culture.

Medium MM
CSL (corn steep liquor)	5 g/l
MOPS (morpholinopropanesulfonic acid)	20 g/l
Glucose (autoclaved separately)	50g/l
(NH4)2SO4
KH2PO4	25 g/l
MgSO4 * 7 H2O	0.1 g/l
CaCl2 * 2 H2O	1.0 g/l
FeSO4 * 7 H2O	10 mg/l
MnSO4 * H2O	10 mg/l
Biotin (sterile-filtered)	0.3 mg/l
Thiamine * HCl (sterile-filtered)	0.2 mg/l
L-Leucine (sterile-filtered)	0.1 g/l
CaCO3	25 g/l

[0065] The CSL, MOPS and the salt solution were brought to pH 7 with aqueous ammonia and autoclaved. The sterile substrate and vitamin solutions were then added, as well as the CaCO₃ autoclaved in the dry state.

[0066] Culturing is carried out in a 10 ml volume in a 100 ml conical flask with baffles. Tetracycline (5 mg/l) was added. Culturing was carried out at 33°C and 80% atmospheric humidity.

[0067] After 48 hours, the OD was determined at a measurement wavelength of 660 nm with a Biomek 1000 (Beckmann Instruments GmbH, München). The amount of lysine formed was determined with an amino acid analyzer from Eppendorf-BioTronik (Hamburg, Germany) by ion exchange chromatography and post-column derivatization with ninhydrin detection.

[0068] The result of the experiment is shown in Table 2.

Table 2

Strain	OD(660)	Lysine HCl g/l
DSM5715/pECgnd	7.7	14.7
DSM5715	7.1	13.7

Example 8

Preparation of a genomic cosmid gene library from Corynebacterium glutamicum ATCC 13032.

[0069] Chromosomal DNA from Corynebacterium glutamicum ATCC 13032 was isolated as described by Tauch et al., (1995, Plasmid 33:168-179), and partly cleaved with the restriction enzyme Sau3AI (Amersham Pharmacia, Freiburg, Germany, Product Description Sau3AI, Code no. 27-0913-02). The DNA fragments were dephosphorylated with shrimp alkaline phosphatase (Roche Molecular Biochemicals, Mannheim, Germany, Product Description SAP, Code no. 1758250). The DNA of the cosmid vector SuperCos1 (Wahl et al. (1987) Proceedings of the National Academy of Sciences USA 84:2160-2164), obtained from Stratagene (La Jolla, USA, Product Description SuperCos1 Cosmid Vektor Kit, Code no. 251301) was cleaved with the restriction enzyme XbaI (Amersham Pharmacia, Freiburg, Germany, Product Description XbaI, Code no. 27-0948-02) and likewise dephosphorylated with shrimp alkaline phosphatase. The cosmid DNA was then cleaved with the restriction enzyme BamHI (Amersham Pharmacia, Freiburg, Germany, Product Description BamHI, Code no. 27-0868-04). The cosmid DNA treated in this manner was mixed with the treated ATCC13032 DNA and the batch was treated with T4 DNA ligase (Amersham Pharmacia, Freiburg, Germany, Product Description T4-DNA-Ligase, Code no. 27-0870-04). The ligation mixture was then packed in phages with the aid of Gigapack II XL Packing Extracts (Stratagene, La Jolla, USA, Product Description Gigapack II XL Packing Extract, Code no. 200217). For infection of the E. coli strain NM554 (Raleigh et al. 1988, Nucleic Acid Research 16:1563-1575) the cells were taken up in 10 mM MgSO₄ and mixed with an aliquot of the phage suspension. The infection and titering of the cosmid library were carried out as described by Sambrook et al. (1989, Molecular Cloning: A laboratory Manual, Cold Spring Harbor), the cells being plated out on LB agar (Lennox, 1955, Virology 1:190) + 100 µg/ml ampicillin. After incubation overnight at 37°C, recombinant individual clones were selected.

Example 9

Isolation and sequencing of the poxB gene

[0070] The cosmid DNA of an individual colony (Example 8) was isolated with the Qiaprep Spin Miniprep Kit (Product No. 27106, Qiagen, Hilden, Germany) in accordance with the manufacturer's instructions and partly cleaved with the restriction enzyme Sau3AI (Amersham Pharmacia, Freiburg, Germany, Product Description Sau3AI, Product No. 27-0913-02). The DNA fragments were dephosphorylated with shrimp alkaline phosphatase (Roche Molecular Biochemicals, Mannheim, Germany, Product Description SAP, Product No. 1758250). After separation by gel electrophoresis, the cosmid fragments in the size range of 1500 to 2000 bp were isolated with the QiaExII Gel Extraction Kit (Product No. 20021, Qiagen, Hilden, Germany). The DNA of the sequencing vector pZero-1, obtained from Invitrogen (Groningen, Holland, Product Description Zero Background Cloning Kit, Product No. K2500-01) was cleaved with the restriction enzyme BamHI (Amersham Pharmacia, Freiburg, Germany, Product Description BamHI, Product No. 27-0868-04). The ligation of the cosmid fragments in the sequencing vector pZero-1 was carried out as described by Sambrook et al. (1989, Molecular Cloning: A laboratory Manual, Cold Spring Harbor), the DNA mixture being incubated overnight with T4 ligase (Pharmacia Biotech, Freiburg, Germany). This ligation mixture was then electroporated (Tauch et al. 1994, FEMS Microbiol Letters, 123:343-7) into the E. coli strain DH5αMCR (Grant, 1990, Proceedings of the National Academy of Sciences U.S.A., 87:4645-4649) and plated out on LB agar (Lennox, 1955, Virology, 1:190) with 50 µg/ml zeocin. The plasmid preparation of the recombinant clones was carried out with Biorobot 9600 (Product No. 900200, Qiagen, Hilden, Germany). The sequencing was carried out by the dideoxy chain-stopping method of Sanger et al. (1977, Proceedings of the National Academies of Sciences U.S.A., 74:5463-5467) with modifications according to Zimmermann et al. (1990, Nucleic Acids Research, 18:1067). The "RR dRhodamin Terminator Cycle Sequencing Kit" from PE Applied Biosystems(Product No. 403044, Weiterstadt, Germany) was used. The separation by gel electrophoresis and analysis of the sequencing reaction were carried out in a "Rotiphoresis NF Acrylamide/Bisacrylamide" Gel (29:1) (Product No. A124.1, Roth, Karlsruhe, Germany) with the "ABI Prism 377" sequencer from PE Applied Biosystems (Weiterstadt, Germany).

[0071] The raw sequence data obtained were then processed using the Staden program package (1986, Nucleic Acids Research, 14:217-231) version 97-0. The individual sequences of the pZerol derivatives were assembled to a continuous contig. The computer-assisted coding region analysis were prepared with the XNIP program (Staden, 1986, Nucleic Acids Research 14:217-231). Further analyses were carried out with the "BLAST search program" (Altschul et al., 1997, Nucleic Acids Research 25:3389-3402), against the non-redundant databank of the "National Center for Biotechnology Information" (NCBI, Bethesda, MD, USA).

[0072] The resulting nucleotide sequence is shown in SEQ ID No. 4. Analysis of the nucleotide sequence showed an open reading frame of 1737 base pairs, which was called the poxB gene. The poxB gene codes for a polypeptide of 579 amino acids (SEQ ID NO. 5).

Example 10

Preparation of an integration vector for integration mutagenesis of the poxB gene

[0073] From the strain ATCC 13032, chromosomal DNA was isolated by the method of Eikmanns et al. (Microbiology 140: 1817 - 1828 (1994)). On the basis of the sequence of the poxB gene known for C. glutamicum from Example 9, the following oligonucleotides were chosen for the polymerase chain reaction:

[0074] The primers shown were synthesized by MWG Biotech (Ebersberg, Germany) and the PCR reaction was carried out by the standard PCR method of Innis et al. (PCR protocols. A guide to methods and applications, 1990, Academic Press) with Pwo-Polymerase from Boehringer. With the aid of the polymerase chain reaction, a DNA fragment approx. 0.9 kb in size was isolated, this carrying an internal fragment of the poxB gene and being shown in SEQ ID No. 6.

[0075] The amplified DNA fragment was ligated with the TOPO TA Cloning Kit from Invitrogen Corporation (Carlsbad, CA, USA; Catalogue Number K4500-01) in the vector pCR2.1-TOPO (Mead at al. (1991) Bio/Technology 9:657-663). The E. coli Stamm DH5α was then electroporated with the ligation batch (Hanahan, In: DNA cloning. A practical approach. Vol.I. IRL-Press, Oxford, Washington DC, USA, 1985). Selection for plasmid-carrying cells was made by plating out the transformation batch on LB agar (Sambrook et al., Molecular cloning: a laboratory manual. 2^nd Ed. Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., 1989), which had been supplemented with 25 mg/l kanamycin. Plasmid DNA was isolated from a transformant with the aid of the QIAprep Spin Miniprep Kit from Qiagen and checked by restriction with the restriction enzyme EcoRI and subsequent agarose gel electrophoresis (0.8%). The plasmid was called pCR2.1poxBint (Figure 4).

[0076] Plasmid pCR2.1poxBint has been deposited in the form of the strain Escherichia coli DH5α/pCR2.1poxBint as DSM 13114 at the Deutsche Sammlung für Mikroorganismen und Zellkulturen (DSMZ = German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany) in accordance with the Budapest Treaty.

Example 11

Integration mutagenesis of the poxB gene in the lysine producer DSM 5715

[0077] The vector pCR2.1poxBint mentioned in Example 10 was electroporated by the electroporation method of Tauch et al.(FEMS Microbiological Letters, 123:343-347 (1994)) in Corynebacterium glutamicum DSM 5715. Strain DSM 5715 is an AEC-resistant lysine producer. The vector pCR2.1poxBint cannot replicate independently in DSM5715 and is retained in the cell only if it has integrated into the chromosome of DSM 5715. Selection of clones with pCR2.1poxBint integrated into the chromosome was carried out by plating out the electroporation batch on LB agar (Sambrook et al., Molecular cloning: a laboratory manual. 2^nd Ed. Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.), which had been supplemented with 15 mg/l kanamycin. For detection of the integration, the poxBint fragment was labelled with the Dig hybridization kit from Boehringer by the method of "The DIG System Users Guide for Filter Hybridization" of Boehringer Mannheim GmbH (Mannheim, Germany, 1993). Chromosomal DNA of a potential integrant was isolated by the method of Eikmanns et al. (Microbiology 140: 1817 - 1828 (1994)) and in each case cleaved with the restriction enzymes SalI, SacI and HindIII. The fragments formed were separated by agarose gel electrophoresis and hybridized at 68°C with the Dig hybrization kit from Boehringer. The plasmid pCR2.1poxBint mentioned in Example 9 had been inserted into the chromosome of DSM5715 within the chromosomal poXB gene. The strain was called DSM5715::pCR2.1poxBint.

Example 12

Effect of over-expression of the gnd gene with simultaneous elimination of the poxB gene on the preparation of lysine

12.1 Preparation of the strain

[0078] DSM5715::pCR2.1poxBint/pECgnd

[0079] The strain DSM5715::pCR2.1poxBint was transformed with the plasmid pECgnd using the electroporation method described by Liebl et al., (FEMS Microbiology Letters, 53:299-303 (1989)). Selection of the transformants took place on LBHIS agar comprising 18.5 g/l brain-heart infusion broth, 0.5 M sorbitol, 5 g/l Bacto-tryptone, 2.5 g/l Bacto-yeast extract, 5 g/l NaCl and 18 g/l Bacto-agar, which had been supplemented with 5 mg/l tetracycline and 25 mg/l kanamycin. Incubation was carried out for 2 days at 33°C.

[0080] Plasmid DNA was isolated in each case from a transformant by conventional methods (Peters-Wendisch et al., 1998, Microbiology 144, 915 -927), cleaved with the restriction endonuclease AccI, and the plasmid was checked by subsequent agarose gel electrophoresis. The strain obtained in this way was called DSM5715:pCR2.1poxBint/pECgnd.

12.2 Preparation of L-lysine

[0081] The C. glutamicum strain DSM5715::pCR2.1poxBint/pECgnd obtained in Example 12.1 was cultured in a nutrient medium suitable for the production of lysine and the lysine content in the culture supernatant was determined.

[0082] For this, the strain was first incubated on an agar plate with the corresponding antibiotic (brain-heart agar with tetracycline (5 mg/l) and kanamycin (25 mg/l)) for 24 hours at 33°C. The cultures of the comparison strains were supplemented according to their resistance to antibiotics. Starting from this agar plate culture, a preculture was seeded (10 ml medium in a 100 ml conical flask). The complete medium CgIII was used as the medium for the preculture.

Medium Cg III
NaCl	2.5 g/l
Bacto-Peptone	10 g/l
Bacto-Yeast extract	10 g/l
Glucose (autoclaved separately)	2% (w/v)

[0083] The pH was brought to pH 7.4

[0084] Tetracycline (5 mg/l) and kanamycin (25 mg/l) were added to this. The preculture was incubated for 16 hours at 33°C at 240 rpm on a shaking machine. A main culture was seeded from this preculture such that the initial OD (660nm) of the main culture was 0.1. Medium MM was used for the main culture.

Medium MM
CSL (corn steep liquor)	5 g/l
MOPS (morpholinopropanesulfonic acid)	20 g/l
Glucose (autoclaved separately)	58 g/l

(NH4)2SO4	25 g/l
KH2PO4	0.1 g/l
MgSO4 * 7 H2O	1.0 g/l
CaCl2 * 2 H2O	10 mg/l
FeSO4 * 7 H2O	10 mg/l
MnSO4 * H2O	5.0mg/l
Biotin (sterile-filtered)	0.3 mg/l
Thiamine * HCl (sterile-filtered)	0.2 mg/l
L-Leucine (sterile-filtered)	0.1 g/l
CaCO3	25 g/l

[0085] The CSL, MOPS and the salt solution were brought to pH 7 with aqueous ammonia and autoclaved. The sterile substrate and vitamin solutions were then added, as well as the CaCO₃ autoclaved in the dry state.

[0086] Culturing is carried out in a 10 ml volume in a 100 ml conical flask with baffles. Tetracycline (5 mg/l) and kanamycin (25 mg/l) were added. Culturing was carried out at 33°C and 80% atmospheric humidity.

[0087] After 72 hours, the OD was determined at a measurement wavelength of 660 nm with a Biomek 1000 (Beckmann Instruments GmbH, München). The amount of lysine formed was determined with an amino acid analyzer from Eppendorf-BioTronik (Hamburg, Germany) by ion exchange chromatography and post-column derivatization with ninhydrin detection.

[0088] The result of the experiment is shown in Table 3.

Table 3

Strain	OD	L-Lysine HCl g/l
DSM5715	10.8	16.0
DSM5715/pECgnd	7.6	16.5
DSM5715::pCR2.1poxBint	7.1	16.7
DSM5715::pCR2.1poxBint/ pECgnd	7.2	17.1

SEQUENCE PROTOCOL

[0089] 

<110> National University of Ireland, Galway Degussa-Hüls AG

<120> Process for the fermentative preparation of L-amino acids using coryneform bacteria.

<130> 990229 BT

<140>
<141>

<160> 6

<170> PatentIn Ver. 2.1

<210> 1
<211> 252
<212> DNA
<213> Corynebacterium glutamicum

<400> 1

<210> 2
<211> 2335
<212> DNA
<213> Corynebacterium glutamicum

<220>
<221> CDS
<222> (474)..(1850)
<223> gnd

<400> 2

<210> 3
<211> 459
<212> PRT
<213> Corynebacterium glutamicum

<400> 3

<210> 4
<211> 2160
<212> DNA
<213> Corynebacterium glutamicum

<220>
<221> CDS
<222> (327)..(2063)
<223> poxB

<400> 4

<210> 5
<211> 579
<212> PRT
<213> Corynebacterium glutamicum

<400> 5

<210> 6
<211> 875
<212> DNA
<213> Corynebacterium glutamicum

<400> 6

Claims

1. A process for the preparation of L-amino acids by fermentation of coryneform bacteria which comprises carrying out the following steps:

a) fermentation of the desired L-amino acid-producing bacteria in which at least the gnd gene is amplified and at least the poxB gene is attenuated,

b) concentration of the L-amino acid in the medium or in the cells of the bacteria and

c) isolation of the L-amino acid produced.

2. The process as claimed in claim 1, wherein bacteria in which further genes of the biosynthesis pathway of the desired L-amino acid are additionally amplified, in particular over-expressed, are employed.

3. The process as claimed in claim 1, wherein coryneform bacteria which prepare L-threonine, L-lysine, L-isoleucine or L-tryptophan are used.

4. The process as claimed in claim 3, wherein coryneform bacteria which prepare L-lysine are used.

5. The process as claimed in claim 3, wherein coryneform bacteria which prepare L-threonine are used.

6. A process for the fermentative preparation of L-lysine as claimed in claim 2, wherein in the coryneform microorganisms which in particular already produce L-lysine, one or more genes chosen from the group consisting of

6.1 the dapA gene which codes for dihydrodipicolinate synthase,

6.2 the lysC gene which codes for a feed back resistant aspartate kinase,

6.3 the gap gene which codes for glyceraldehyde 3-phosphate dehydrogenase,

6.4 the pyc gene which codes for pyruvate carboxylase,

6.5 the tkt gene which codes for transketolase,

6.6 the zwf gene which codes for glucose 6-phosphate dehydrogenase, and

6.7 the lysE gene which codes for lysine export,

is or are amplified, in particular over-expressed, at the same time.

7. A process for the fermentative preparation of L-threonine as claimed in claim 2, wherein in the coryneform microorganisms which in particular already produce L-threonine, one or more genes chosen from the group consisting of

7.1 the hom gene which codes for homoserine dehydrogenase or the hom^dr allele which codes for a "feed back resistant" homoserine dehydrogenase,

7.2 the gap gene which codes for glyceraldehyde 3-phosphate dehydrogenase,

7.3 the pyc gene which codes for pyruvate carboxylase,

7.4 the mqo gene which codes for malate:quinone oxidoreductase,

7.5 the tkt gene which codes for transketolase,

7.6 the zwf gene which codes for glucose 6-phosphate dehydrogenase, and

7.7 the thrE gene which codes for threonine export,

is or are amplified, in particular over-expressed, at the same time.

8. The process as claimed in claims 2 to 7, wherein to achieve the amplification, the number of copies of the genes or nucleotide sequences is increased by transformation of the microorganisms with plasmid vectors which carry these genes or nucleotide sequences.

Ansprüche

1. Verfahren zur Herstellung von L-Aminosäuren durch Fermentation von Coryneform-Bakterium, umfassend die Ausführung der folgenden Schritte:

a) Fermentieren der gewünschten L-Aminosäureproduzierenden Bakterien, in denen wenigstens das gnd-Gen amplifiziert und wenigstens das poxB-Gen attenuiert wird,

b) Konzentrieren der L-Aminosäure im Medium oder in den Zellen der Bakterien und

c) Isolieren der produzierten L-Aminosäure.

2. Verfahren nach Anspruch 1, bei dem Bakterien, in denen weitere Gene des Biosyntheseweges der gewünschten L-Aminosäure zusätzlich amplifiziert, insbesondere überexprimiert werden, verwendet werden.

3. Verfahren nach Anspruch 1, bei dem Coryneform-Bakterien, die L-Threonin, L-Lysin, L-Isoleucin oder L-Tryptophan herstellen, verwendet werden.

4. Verfahren nach Anspruch 3, bei dem Coryneform-Bakterien, die L-Lysin herstellen, verwendet werden.

5. Verfahren nach Anspruch 3, bei dem Coryneform-Bakterien, die L-Threonin herstellen, verwendet werden.

6. Verfahren zur fermentativen Herstellung von L-Lysin nach Anspruch 2, wobei in den Coryneform-Mikroorganismen, die insbesondere bereits L-Lysin produzieren, ein oder mehrere Gene ausgewählt aus der Gruppe bestehend aus:

6.1 dem dapA-Gen, das Dihydrodipicolinatsynthase codiert,

6.2 dem lysC-Gen, das feedbackresistente Aspartatkinase codiert,

6.3 dem gap-Gen, das Glyceraldehyd-3-phosphatdehydrogenase codiert,

6.4 dem pyc-Gen, das Pyruvatcarboxylase codiert,

6.5 dem tkt-Gen, das Transketolase codiert,

6.6 dem zwf-Gen, das Glucose-6-phosphatdehydrogenase codiert, und

6.7 dem lysE-Gen, das Lysinexport codiert,

gleichzeitig amplifiziert, insbesondere überexprimiert, wird oder werden.

7. Verfahren zur fermentativen Herstellung von L-Threonin nach Anspruch 2, wobei in den Coryneform-Mikroorganismen, die insbesondere bereits L-Threonin produzieren, ein oder mehrere Gene ausgewählt aus der Gruppe bestehend aus:

7.1 dem hom-Gen, das Homoserindehydrogenase codiert, oder dem hom^dr-Allel, das eine "feedbackresistente" Homoserindehydrogenase codiert,

7.2 dem gap-Gen, das Glyeraldehyd-3-phosphatdehydrogenase codiert,

7.3 dem pyc-Gen, das Pyruvatcarboxylase codiert,

7.4 dem mqo-Gen, das Malat:Chinon-Oxidoreductase codiert,

7.5 dem tkt-Gen, das Transketolase codiert,

7.6 dem zwf-Gen, das Glucose-6-phospatdehydrogenase codiert, und

7.7 dem thrE-Gen, das Threoninexport codiert,

gleichzeitig amplifiziert, insbesondere überexprimiert, wird oder werden.

8. Verfahren nach einem der Ansprüche 2 bis 7, wobei zum Erzielen der Amplifizierung die Anzahl von Kopien der Gene oder Nucleotidsequenzen durch Transformation der Mikroorganismen mit Plasmidvektoren erhöht wird, die diese Gene oder Nucleotidsequenzen tragen.

Revendications

1. Procédé pour la préparation d'acides aminés L par une fermentation de bactéries de type coryneforme qui comprend la réalisation des étapes suivantes :

a) fermentation des bactéries produisant l'acide aminé L souhaité dans lesquelles au moins le gène gnd est amplifié et au moins le gène poxB est atténué,

b) concentration de l'acide aminé L dans le milieu ou dans les cellules des bactéries et

c) isolation de l'acide aminé-L produit.

2. Procédé selon la revendication 1, dans lequel on utilise des bactéries dans lesquelles d'autres gènes de la voie de biosynthèse de l'acide aminé-L souhaité sont additionnellement amplifiés, en particulier surexprimés.

3. Procédé selon la revendication 1, dans lequel on utilise des bactéries de type coryneforme qui préparent de la L-thréonine, de la L-lysine, de la L-isoleucine ou du L-tryptophane.

4. Procédé selon la revendication 3, dans lequel on utilise des bactéries de type coryneforme qui préparent de la L-lysine.

5. Procédé selon la revendication 3, dans lequel on utilise des bactéries de type coryneforme qui préparent de la L-thréonine.

6. Procédé pour la préparation par fermentation de la L-lysine selon la revendication 2, dans lequel, dans les microorganismes de type coryneforme qui en particulier produisent déjà de la L-lysine, un ou plusieurs gènes choisis dans le groupe constitué :

6.1 du gène dapA qui code pour une dihydrodipicolinate synthétase,

6.2 du gène lysC qui code pour une aspartate kinase résistante à l'inhibition rétroactive,

6.3 du gène gap qui code pour une glycéraldéhyde 3-phosphate déshydrogénase,

6.4 du gène pyc qui code pour une pyruvate carboxylase,

6.5 du gène tkt qui code pour une transcétolase

6.6 du gène zwf qui code pour une glucose 6-phosphate déshydrogénase, et

6.7 du gène lyse qui code pour une exportation de la lysine,

est ou sont simultanément ampliflé(s), en particulier surexprimé(s).

7. Procédé pour la préparation par fermentation de la L-thréonine selon la revendication 2, dans lequel, dans les microorganismes de type coryneforme qui en particulier produisent déjà de la L-thréonine, un ou plusieurs gènes choisis dans le groupe constitué :

7.1 du gène hom qui code pour une homosérine déshydrogénase ou de l'allèle hom^dr qui code pour une homosérine déshydrogénase «résistante à l'inhibition rétroactive»,

7.2 du gène gap qui code pour la glycéraldéhyde 3-phosphate déshydrogénase,

7.3 du gène pyc qui code pour une pyruvate carboxylase,

7.4 du gène mqo qui code pour une malate/quinone oxydoréductase,

7.5 du gène tkt qui code pour une transcétolase,

7.6 du gène zwf qui code pour une glucose 6-phosphate déshydrogénase, et

7,7 du gène thrE qui code pour une exportation de la thréonine,

est ou sont simultanément amplifié(s), en particulier surexprimé(s).

8. Procédé selon les revendications 2 à 7, dans lequel, pour réaliser l'amplification, on augmente le nombre de copies des gènes ou des séquences nucléotidiques par une transformation des microorganismes avec des vecteurs plasmidiques qui portent ces gènes ou séquences nucléotidiques.

Drawing