Yeast, yeast extract containing gamma-glu-abu, and a method for producing the same

Abstract

A yeast extract containing 0.2% or more of γ-Glu-Abu based on dry weight of the yeast extract is produced by culturing a yeast, such as Saccharomyces cervisiae or Candida utilis , in a medium containing a compound selected from Abu (L-2-aminobutyric acid) and γ-Glu-Abu (L-γ-glutamyl-L-2-aminobutyric acid), and preparing a yeast extract from the obtained cells.

1 . A yeast extract containing 0.2% or more of γ-Glu-Abu based on dry weight of the yeast extract. 
     
     
         2 . A yeast extract according to  claim 1 , which contains 0.5% or more of γ-Glu-Abu based on dry weight of the yeast extract. 
     
     
         3 . A yeast extract according to  claim 1 , which contains 1.0% or more of γ-Glu-Abu based on dry weight of the yeast extract. 
     
     
         4 . The yeast extract according to  claim 1 , wherein the yeast belongs to the genus  Saccharomyces  or  Candida.    
     
     
         5 . The yeast extract according to  claim 2 , wherein the yeast belongs to the genus  Saccharomyces  or  Candida.    
     
     
         6 . The yeast extract according to  claim 3 , wherein the yeast belongs to the genus  Saccharomyces  or  Candida.    
     
     
         7 . The yeast extract according to  claim 4 , which is obtained from  Saccharomyces cervisiae  or  Candida utilis.    
     
     
         8 . The yeast extract according to  claim 5 , which is obtained from  Saccharomyces cervisiae  or  Candida utilis.    
     
     
         9 . The yeast extract according to  claim 6 , which is obtained from  Saccharomyces cervisiae  or  Candida utilis.    
     
     
         10 . A method for producing a yeast extract containing γ-Glu-Abu, which comprises culturing a yeast in a medium to which a compound selected from Abu and γ-Glu-Abu is added, and preparing a yeast extract from the obtained cells. 
     
     
         11 . The method according to  claim 10 , wherein the compound is added to the medium in an amount of 10 ppm or more in the case of Abu, or 1 ppm or more in the case of γ-Glu-Abu, and the yeast extract contains 0.2% or more of γ-Glu-Abu based on dry weight of the yeast extract. 
     
     
         12 . The method according to  claim 10 , wherein the yeast belongs to the genus  Saccharomyces  or  Candida.    
     
     
         13 . The method according to  claim 11 , wherein the yeast belongs to the genus  Saccharomyces  or  Candida.    
     
     
         14 . The method according to  claim 12 , wherein the yeast is  Saccharomyces cervisiae  or  Candida utilis.    
     
     
         15 . The method according to  claim 13 , wherein the yeast is  Saccharomyces cervisiae  or  Candida utilis.    
     
     
         16 . The method according to  claim 10 , wherein the yeast has one or both of the following characteristics:
 (a) γ-glutamylcysteine synthetase activity is enhanced,   (b) glutathione synthetase activity is attenuated.   
     
     
         17 . A yeast having an increased γ-Glu-Abu content, which has been modified so that
 activity of aminotransferase or/and activity of α-ketobutyric acid synthetase are enhanced, and, 
 activity of γ-glutamylcysteine synthetase is enhanced, or/and activity of glutathione synthetase is attenuated. 
 
     
     
         18 . The yeast according to  claim 17 , wherein the aminotransferase is an enzyme encoded by the BAT1 gene. 
     
     
         19 . The yeast according to  claim 17 , wherein the aminotransferase is an enzyme encoded by the UGA1 gene. 
     
     
         20 . The yeast according to  claim 17 , wherein the α-ketobutyric acid synthetase is an enzyme encoded by the CHA1 gene. 
     
     
         21 . The yeast according to  claim 17 , wherein a peptidase activity is further attenuated. 
     
     
         22 . A yeast extract produced from the yeast according to  claim 18 . 
     
     
         23 . A method for producing a yeast extract containing γ-Glu-Abu, which comprises allowing a γ-glutamyltransferase to act on a yeast extract raw material to which Abu has been added. 
     
     
         24 . The method according to  claim 23 , wherein Abu is added in an amount of 0.1% or more based on dry weight of the yeast extract raw material, and the yeast extract contains 0.2% or more of Abu based on dry weight of the yeast extract.