YEAST MUTANT AND YEAST EXTRACT
A natural yeast extract which is rich in glutamic acid and therefore has an impact at first taste. Further, provided is a yeast extract which is also rich in 5′-guanylic acid or 5′-inosinic acid and therefore has strong umami. Further, provided is a yeast mutant capable of accumulating a large amount of glutamic acid, glutamine and ribonucleic acid for obtaining such a yeast extract. A yeast mutant to which resistance to organic acids and analogues thereof has been imparted by inducing spontaneous mutation, accumulates a significant amount, i.e., 10% by weight or more of the total of free glutamic acid and glutamine in the cell, and further accumulates 5% by weight or more of a ribonucleic acid. The yeast extract produced by using this strain contains 20% by weight or more of L-glutamic acid, and further contains 3% by weight or more of 5′-IG.
1 . A yeast mutant, wherein free glutamic acid and glutamine are accumulated in a total amount of 10% or more, based on a weight of a dry cell.
2 . The yeast mutant according to claim 1 , wherein ribonucleic acid (RNA) is further accumulated in an amount of 5% or more, based on a weight of a dry cell.
3 . The yeast mutant according to claim 1 , wherein the yeast mutant is tolerant to ethyl bromopyruvate.
4 . The yeast mutant according to claim 1 , wherein the yeast mutant is tolerant to ethyl bromopyruvate and 2-oxoglutaric acid.
5 . The yeast mutant according to claim 1 , wherein the yeast mutant is Candida utilis 36D61 (accession number: FERM BP-11103).
6 . A yeast extract produced from the yeast mutant as claimed in claim 1 , wherein the yeast extract contains L-glutamic acid in an amount of 20% by weight or more converted into an amount of a sodium salt thereof.
7 . The yeast extract according to claim 6 , wherein the yeast extract further contains 5′-guanylic acid and 5′-inosinic acid or 5′-adenylic acid in a total amount of 3% by weight or more.