Microorganism Producing L-Methionine Precursor and Method of Producing L-Methionine and Organic Acid from the L-Methionine Precursor

Abstract

The present invention relates to a method for producing L-methionine, comprising: i) culturing an L-methionine precursor-producing microorganism strain in a fermentation solution, so that the L-methionine precursor accumulates in the solution; and ii) mixing a converting enzyme and methylmercaptan or its salts with at least a portion of the solution to convert the accumulated L-methionine precursor into L-methionine, as well as to microorganism strains used in each step.

What is claimed is: 
     
         1 . A method for producing L-methionine, comprising:
 i) culturing an L-methionine precursor-producing microorganism strain in a fermentation solution, so that the L-methionine precursor accumulates in the fermentation solution; and   ii) mixing a converting enzyme and methylmercaptan or its salts with at least a portion of the fermentation solution to convert the accumulated L-methionine precursor into L-methionine.   
     
     
         2 . The method of  claim 1 , wherein said the L-methionine precursor is an O-acylhomoserine. 
     
     
         3 . The method of  claim 1 , wherein the L-methionine precursor-producing microorganism strain of step i) is selected from the group consisting of  Escherichia  sp.,  Erwinia  sp.,  Serratia  sp.,  Corynebacterium  sp.,  Pseudomonas  sp.,  Salmonellar  sp.,  Brevibacterium  sp., and yeasts. 
     
     
         4 . The method of  claim 3 , wherein the L-methionine precursor-producing microorganism strain is selected from  Escherichia  sp. and  Corynebacterium  sp. 
     
     
         5 . The method of  claim 4 , wherein the L-methionine precursor-producing microorganism strain is  Escherichia coli.    
     
     
         6 . The method of  claim 4 , wherein the L-methionine precursor-producing microorganism strain is  Corynebacterium glutamicum.    
     
     
         7 . The method of  claim 1 , wherein said at least a portion of the fermentation solution is a substantially cell-free solution. 
     
     
         8 . The method according to  claim 1 , wherein the converting enzyme is provided as a cell-free extract of a microbial culture. 
     
     
         9 . The method according to  claim 1 , wherein the converting enzyme is a recombinant enzyme. 
     
     
         10 . A method for producing L-methionine and organic acid, which comprises the following steps:
 i) producing L-methionine precursor in a fermentation medium by the fermentation of an L-methionine precursor-producing microbial strain, wherein the L-methionine precursor-producing microbial strain is prepared by deleting the activity of cystathionine gamma synthase or O-succinylhomoserine sulfhydrylase or O-acetylhomoserine sulfhydrylase involved in the degradation of L-methionine precursor and by enhancing the activity of homoserine O-succinyl transferase or homoserine O-acetyl transferase involved in L-methionine precursor synthesis from homoserine; and   ii) producing L-methionine and organic acid outside of the L-methionine precursor-producing microbial strain by the enzyme reaction using the L-methionine precursor and methylmercaptan or its salts as substrates, wherein the enzyme reaction is performed by an enzyme not present in said precursor-producing strain.   
     
     
         11 . The method of  claim 10 , wherein the L-methionine precursor-producing microbial strain is selected from the group consisting of  Escherichia  sp. and  Corynebacterium  sp. 
     
     
         12 . The method of  claim 10 , wherein the cystathionine gamma synthase or O-succinylhomoserine sulfhydrylase or O-acetylhomoserine sulfhydrylase of step i) is encoded, respectively, by metB, metZ, and metY, or functional mutants thereof. 
     
     
         13 . The method of  claim 10 , wherein the L-methionine precursor-producing microbial strain is a strain whose threonine, isoleucine or lysine biosynthesis pathway is weakened or deleted. 
     
     
         14 . The method of  claim 10 , wherein the enzyme of step ii) is from a strain selected from the group consisting of  Escherichia  sp.,  Erwinia  sp.,  Serratia  sp.,  Providencia sp.,  Corynebacterium  sp.,  Pseudomonas  sp.,  Leptospira  sp.,  Salmonellar  sp.,  Brevibacterium  sp.,  Hyphomonas  sp.,  Chromobacterium  sp.,  Nocardia  sp., and yeasts. 
     
     
         15 . The method of  claim 10 , wherein the enzyme of step ii) is from a strain selected from the group consisting of:  Escherichia Coli, Pseudomonas aurogenosa, Pseudomonas putida, Corynebacteria glutamicum, Leptospira meyeri, Saccharomyces cerevisiae, Chromobacterium Violaceum, Nocardia Farcinica, Bradyrhizobium Japonicum, Hyphomonas Neptunium, Methylococcus Capsulatus, Methylobacillus Flagellatus, Nitrosomonas Europaea, Klebsiella Pneumoniae, Bacillus Subtilis, Shigella flexneri, Colwellia Psychrerythraea,  and  Salmonella enterica  serovar Paratyphi A. 
     
     
         17 . A method for producing L-methionine, comprising:
 i) separating fermentation solution from a culture of an L-methionine precursor-producing microorganism strain to produce a supernatant; and   ii) contacting a cell-free extract from a second culture with at least a portion of said supernatant in the presence of methylmercaptan or its salts to convert L-methionine precursor in said supernatant into L-methionine   
     
     
         18 . The method of  claim 17 , wherein the supernatant contains O-acylhomoserine. 
     
     
         19 . The method according to  claim 17 , wherein the second culture is selected from the group consisting of  Escherichia  sp.,  Erwinia  sp.,  Serratia  sp.,  Providencia  sp.,  Corynebacterium  sp.,  Pseudomonas  sp.,  Leptospira  sp.,  Salmonellar  sp.,  Brevibacterium  sp.,  Hyphomonas  sp.,  Chromobacterium  sp. and  Nocardia  sp., and yeasts. 
     
     
         20 . The method of  claim 17 , wherein the second culture is selected from the group consisting of  Escherichia Coli, Pseudomonas aurogenosa, Pseudomonas putida, Corynebacteria glutamicum, Leptospira meyeri, Saccharomyces cerevisiae, Chromobacterium Violaceum, Nocardia Farcinica, Bradyrhizobium Japonicum, Hyphomonas Neptunium, Methylococcus Capsulatus, Methylobacillus Flagellatus, Nitrosomonas Europaea, Klebsiella Pneumoniae, Bacillus Subtilis,  and  Shigella flexneri.