Method for obtaining low ethanol-producing yeast strains, yeast strains obtained therefrom and their use

Patent metadata

Field	Value
Publication number	US-2016348192-A1
Application number	US-201515115151-A
Country	US
Kind code	A1
Filing date	Jan 30, 2015
Priority date	Jan 31, 2014
Publication date	Dec 1, 2016
Grant date	—

Abstract

The present disclosure concerns a process for obtaining a variant yeast strain capable of producing less ethanol in an alcoholic fermentation process than its corresponding ancestral strain. The variant yeast strain is obtained by culturing the ancestral strain in the presence of increasing concentrations of a salt capable of causing an hyperosmotic stress to the ancestral yeast strain. The present disclosure also concerns variant yeast strain obtained from this process (for example the variant yeast strain deposited at Institut Pasteur, on Jan. 9, 2014, under accession number CNCM I-4832, the variant yeast strain deposited at Institut Pasteur, on Oct. 18, 2012 under accession number CNCM I-4684, the variant yeast strain deposited at Institut Pasteur, on Oct. 18, 2012 under accession number CNCM I-4685 and/or the variant yeast strain deposited at Institut Pasteur on Jan. 28, 2015 under accession number CNCM I-4952) as well as processes using the variant yeast strain (wine fermentation for example).

First claim

1 . A process for obtaining a variant yeast strain capable of producing, when compared to an ancestral yeast strain, more glycerol and less ethanol during an alcoholic fermentation process, said process comprising:
a) culturing the ancestral yeast strain in a first culture medium comprising a salt capable of causing hyperosmotic stress to the ancestral yeast strain, wherein the ancestral yeast strain is cultured in increasing salt concentrations and under conditions to achieve glucose depletion in the first culture medium so as to obtain a first cultured yeast strain; and b) culturing the first cultured yeast strain in a second culture medium comprising the salt that is capable of causing hyperosmotic stress to the ancestral yeast strain, wherein the first cultured yeast strain is cultured at a fixed salt concentration and under conditions to achieve glucose depletion in the second culture medium so as to obtain the variant yeast strain; wherein
the salt has a countercaftion which is different than a sodium cation; and
the concentration of the salt in the second culture medium is higher than the concentration of the salt in the first culture medium.

2 . The process of claim 1 , wherein either or both of (i) concentration of the salt in the first culture medium is between about 1.25 M and less than about 2.4 M and (ii) concentration of the salt in the second culture medium is at least about 2.4 M.

3 . The process of claim 1 , further comprising, at step a), increasing the salt concentration weekly or increasing the salt concentration monthly.

4 . The process of claim 1 , wherein the first culture medium comprises glucose and the process further comprises, at step a), culturing the ancestral yeast strain in the first culture medium in which glucose concentration is decreased weekly or in which glucose concentration is decreased monthly, wherein the glucose concentration in the first culture medium is between about 14.0% and about 8.0% (w/v) with respect to the-total volume of the first culture medium.

5 . The process of claim 1 , wherein the second culture medium comprises glucose and the process further comprises, at step b), culturing the first cultured yeast strain at a fixed glucose concentration wherein the fixed glucose concentration of the second culture medium is about 8.0% (w/v) with respect to total volume of the second culture medium.

6 . process of claim 1 , further comprising mating haploid spores of the variant yeast strain to obtain a variant hybrid strain.

7 . The process of claim 1 , wherein the salt has a potassium countercation.

8 . The process of claim 7 , wherein the salt is KCl.

9 . The process of claim 1 , wherein the variant yeast strain is obtained from a Saccharomyces species.

10 . A variant yeast strain capable of producing, when compared to an ancestral yeast strain, more glycerol and less ethanol in an alcoholic fermentation process, said variant yeast being obtained by the process of claim 1 .

11 . The variant yeast strain of claim 10 which is capable of making a fermented product when contacted with a fermentable source of nutrients, wherein the fermentable source of nutrients is a grape must and the fermented product is wine.

12 . A variant yeast strain deposited at Institut Pasteur, on Jan. 9, 2014, under accession number Collection Nationale des Cultures des Microorganismes (CNCM) I-4832.

13 . A variant yeast strain deposited at Institut Pasteur, on Oct. 18, 2012 under accession number Collection Nationale des Cultures des Microorganismes (CNCM) I-4684.

14 . A variant yeast strain deposited at Institut Pasteur, on Oct. 18, 2012 under accession number Collection Nationale des Cultures des Microorganismes (CNCM) I-4685.

15 . A variant yeast strain deposited at Institut Pasteur, on Jan. 28, 2015 under accession number Collection Nationale des Cultures des Microorganismes (CNCM) I-4952.

16 . A process for making a fermented product, said process comprising contacting the variant yeast strain of claim 10 with a fermentable source of nutrients.

17 . The process of claim 16 , wherein the fermented product is wine and the fermentable source of nutrients is a grape must.

18 . The process of claim 9 , wherein the Saccharomyces species is selected from the group consisting of Saccharomyces arboricolus, Saccharomyces eubayanus, Saccharomyces bayanus, Saccharomyces cerevisiae, Saccharomyces kudriadzevii, Saccharomyces mikatae, Saccharomyces paradoxus, Saccharomyces pastorianus, Saccharomyces carsbergensis, Saccharomyces uvarum and inter-species hybrids thereof.

19 . The variant yeast strain of claim 11 wherein the wine is red wine.

20 . The process of claim 17 wherein the wine is red wine.

Assignees

• Danstar Ferment Ag
• Inst Nat De La Rech Agromomique (Inra)

Inventors

• Tilloy Valentin
• Ortiz-Julien Anne
• Noble Jessica
• Dequin Sylvie

Classifications

• C12N1/36 Primary

  Adaptation or attenuation of cells · CPC title

• C12N1/185

  Saccharomyces isolates · CPC title

• C12N1/16

  Yeasts; Culture media therefor · CPC title

• C12G2200/05

  Use of particular microorganisms in the preparation of wine · CPC title

• C12P7/20

  Glycerol · CPC title