L-Glutamic Acid-Producing Microorganism and a Method for Producing L-Glutamic Acid

Abstract

A coryneform bacterium which has an L-glutamic acid-producing ability and grows at least at the same growth rate as a non-mutated strain or a wild-type strain and has intracellular α-ketoglutarate dehydrogenase activity which is less than half that of the non-mutated or wild-type strain, and is obtained by introducing a mutation into a coding region or an expression control region of the chromosomal odhA gene encoding the E1o subunit of the α-ketoglutarate dehydrogenase complex.

1 . A method for producing L-glutamic acid comprising: 
 a) culturing an L-glutamic acid-producing coryneform bacterium in a culture medium, and    b) collecting L-glutamic acid from the culture medium and/or the bacterium, wherein said bacterium comprises 
 a) intracellular α-ketoglutarate dehydrogenase activity which is less than half that of a non-mutated or wild-type strain, and  
 b) a mutation in a coding region or an expression control region of a chromosomal odhA gene encoding the E1o subunit of the α-ketoglutarate dehydrogenase complex,  
 and wherein said bacterium grows at a rate which is at least 80% as compared to the growth rate of a non-mutated or wild-type strain.  
   
     
     
         2 . The method according to  claim 1 , wherein said odhA gene encodes a protein selected from the group consisting of: 
 (A) a protein comprising an amino acid sequence of SEQ ID NO: 10,    (B) a protein comprising an amino acid sequence of SEQ ID NO: 10,    wherein 1 to 20 amino acids in said protein are substituted, deleted, inserted, or added, and wherein said protein has an activity of the E1o subunit of the α-ketoglutarate dehydrogenase complex,    (C) a protein comprising amino acids 37 to 1257 of SEQ ID NO: 10, and    (D) a protein comprising amino acids 37 to 1257 of SEQ ID NO: 10,    wherein 1 to 20 amino acids in said protein are substituted, deleted, inserted, or added, and wherein said protein has an activity of the E1o subunit of the α-ketoglutarate dehydrogenase complex.    
     
     
         3 . The method according to  claim 1 , wherein said odhA gene is selected from the group consisting of: 
 (a) a gene comprising nucleotides 443 to 4213 of SEQ ID NO: 9,    (b) a gene that is able to hybridize under stringent conditions to a polynucleotide comprising nucleotides 443 to 4213 of SEQ ID NO: 9, and wherein said gene encodes a protein which has the activity of the E1o subunit of the α-ketoglutarate dehydrogenase complex,    (c) a gene comprising nucleotides 551 to 4213 of SEQ ID NO: 9, and    (d) a gene that is able to hybridize under stringent conditions to a polynucleotide comprising nucleotides 551 to 4213 of SEQ ID NO: 9, and wherein said gene encodes a protein which has the activity of the E1o subunit of the α-ketoglutarate dehydrogenase complex    and wherein said stringent conditions comprise washing in 1×SSC and 0.1% SDS at 60° C.    
     
     
         4 . The method according to  claim 1 , wherein said mutation is introduced into a region which encodes a thiamine pyrophosphate binding region.  
     
     
         5 . The method according to  claim 1 , wherein said mutation is introduced into the region comprising nucleotides 2534 to 2548 of SEQ ID NO: 9.  
     
     
         6 . The method according to  claim 1 , wherein said mutation comprises deletion of one or more amino acids in the region comprising amino acids 698 to 702 of SEQ ID NO: 10.  
     
     
         7 . The method according to  claim 1 , wherein said mutation comprises replacement of an amino acid selected from the group consisting of Lys at position 698, Leu at position 699, Arg at position 700, Tyr at position 702, and combinations thereof in the amino acid sequence shown in SEQ ID NO: 10.  
     
     
         8 . The method according to  claim 1 , wherein said mutation is introduced into the region comprising nucleotides 1094 to 1114 of SEQ ID NO: 9.