L-cysteine-producing microorganism and a method for producing L-cysteine

Abstract

L-cysteine is produced by culturing an Escherichia bacterium having L-cysteine producing ability and containing a gene encoding an O-acetylserine sulphydrylase B or MalY regulatory protein that is modified so that cysteine desulfhydrase activity is reduced or eliminated. The bacterium is cultured in a medium to produce and cause accumulation of L-cysteine in the medium, and collecting L-cysteine from the medium.

1 . An  Escherichia  bacterium having L-cysteine-producing ability, wherein said bacterium contains a gene encoding O-acetylserine sulphydrylase B, and wherein said gene is modified so that cysteine desulfhydrase activity is reduced or eliminated. 
     
     
         2 . An  Escherichia  bacterium having L-cysteine producing ability, wherein said bacterium contains a gene encoding MalY regulatory protein, and wherein said gene is modified so that cysteine desulfhydrase activity is reduced or eliminated. 
     
     
         3 . The  Escherichia  bacterium according to  claim 1 , wherein said gene encoding O-acetylserine sulphydrylase B is disrupted. 
     
     
         4 . The  Escherichia  bacterium according to  claim 2 , wherein said gene encoding MalY regulatory protein is disrupted. 
     
     
         5 . The  Escherichia  bacterium according to  claim 1 , wherein activity of an L-cysteine biosynthetic enzyme is enhanced. 
     
     
         6 . The  Escherichia  bacterium according to  claim 5 , wherein said L-cysteine biosynthetic enzyme is serine acetyltransferase. 
     
     
         7 . The  Escherichia  bacterium according to  claim 6 , wherein said serine acetyltransferase is resistant to feedback inhibition by L-cysteine. 
     
     
         8 . The  Escherichia  bacterium according to  claim 1 , wherein said  Escherichia  bacterium is  Escherichia coli.    
     
     
         9 . A method of producing L-cysteine comprising culturing the  Escherichia  bacterium according to  claim 1  in a medium, and collecting L-cysteine from the medium. 
     
     
         10 . The  Escherichia  bacterium according to  claim 2 , wherein activity of an L-cysteine biosynthetic enzyme is enhanced. 
     
     
         11 . The  Escherichia  bacterium according to  claim 2 , wherein said  Escherichia  bacterium is  Escherichia coli.    
     
     
         12 . A method of producing L-cysteine comprising culturing the  Escherichia  bacterium according to  claim 2  in a medium, and collecting L-cysteine from the medium.