Method for producing l-glutamic acid by fermentation accompanied by precipitation

Abstract

A microorganism which can metabolize a carbon source at a specific pH in a liquid medium containing L-glutamic acid at a saturation concentration and the carbon source, and has ability to accumulate L-glutamic acid in an amount exceeding the amount corresponding to the saturation concentration in the liquid medium at the pH; and a method for producing L-glutamic acid by fermentation, which comprises culturing the microorganism in a liquid medium of which pH is adjusted to a pH at which L-glutamic acid is precipitated, to produce and accumulate L-glutamic acid and precipitate L-glutamic acid in the medium.

1 . A method for producing L-glutamic acid by fermentation, which comprises culturing an isolated microorganism in a liquid medium of which pH is adjusted to the pH at which L-glutamic acid is precipitated, to produce and accumulate L-glutamic acid and precipitate L-glutamic acid in the medium, 
 wherein said microorganism can metabolize a carbon source at a specific pH in a liquid medium containing the carbon source and L-glutamic acid at a saturation concentration, and has the ability to accumulate L-glutamic acid in an amount exceeding the amount corresponding to the saturation concentration in the liquid medium at the pH,    wherein the microorganism belongs to the genus  Enterobacter , the genus  Klebsiella , the genus  Pantoea , or the genus  Erwinia , and    wherein said microorganism has at least one of the following characteristics: (a) the microorganism has increased activity, as compared to a corresponding wild-type microorganism, of an enzyme that catalyzes a reaction for biosynthesis of L-glutamic acid; and (b) the microorganism has decreased activity, as compared to a corresponding wild-type microorganism, or deficient activity of an enzyme that catalyzes a reaction of a pathway branching from a biosynthetic pathway of L-glutamic acid and producing a compound other than L-glutamic acid.    
     
     
         2 . The method according to  claim 1 , wherein said microorganism can grow in the liquid medium.  
     
     
         3 . The method according to  claim 1 , wherein the pH is not more than 5.0.  
     
     
         4 . The method according to  claim 1 , wherein in said microorganism an activity of at least one enzyme selected from the group consisting of citrate synthase, phosphoenolpyruvate carboxylase and glutamate dehydrogenase, is increased.  
     
     
         5 . The method according to  claim 1 , wherein in said microorganism the enzyme that catalyzes the reaction of the pathway branching from the biosynthetic pathway of L-glutamic acid and producing the compound other than L-glutamic acid is α-ketoglutarate dehydrogenase.  
     
     
         6 . The method according to  claim 1 , wherein said microorganism belongs to the genus  Enterobacter.    
     
     
         7 . The method according to  claim 6 , wherein said microorganism has a mutation that causes less extracellular secretion of a viscous material compared with a wild strain when cultured in a medium containing a saccharide.