Use of lactic acid bacteria for preparing fermented food products with increased natural sweetness

Patent metadata

Field	Value
Publication number	US-11076609-B2
Application number	US-201916655806-A
Country	US
Kind code	B2
Filing date	Oct 17, 2019
Priority date	Apr 25, 2012
Publication date	Aug 3, 2021
Grant date	Aug 3, 2021

Abstract

Described are mutant Streptococcus thermophilus strains and mutant Lactobacillus delbrueckii subsp. bulgaricus strains that excrete glucose into milk when the milk is inoculated and fermented with such strains. Methods for obtaining such strains without genetic modification are described, including methods for obtaining such Streptococcus thermophilus strains by selecting and isolating from a pool of Streptococcus thermophilus strains derived from a galactose-fermenting Streptococcus thermophilus mother strain a pool of Streptococcus thermophilus strains which are resistant to 2-deoxyglucose, and selecting and isolating from the pool of Streptococcus thermophilus strains which are resistant to 2-deoxyglucose a Streptococcus thermophilus strain which exhibits a growth rate in M17 medium+2% galactose higher than its growth rate in M17 medium+2% glucose. The strains are useful for decreasing the lactose content of a fermented food product and for boosting growth of the probiotic BB-12®.

First claim

The invention claimed is:

1. A method for obtaining a non-genetically modified Streptococcus thermophilus strain that carries a mutation in the DNA sequence of the glcK gene encoding a glucokinase protein, wherein the mutation inactivates the glucokinase protein or has a negative effect on expression of the gene, comprising:
(a) selecting and isolating from a pool of Streptococcus thermophilus strains derived from a galactose-fermenting Streptococcus thermophilus mother strain a pool of Streptococcus thermophilus strains which are resistant to 2-deoxyglucose; and
(b) selecting and isolating from the pool of Streptococcus thermophilus strains which are resistant to 2-deoxyglucose a Streptococcus thermophilus strain which exhibits a growth rate in M17 medium+2% galactose higher than its growth rate in M17 medium+2% glucose.

2. A method according to claim 1 , further comprising:
(c) selecting and isolating from a pool of 2-deoxyglucose resistant Streptococcus thermophilus strains derived from the Streptococcus thermophilus strain selected in step (b) a Streptococcus thermophilus strain that grows in M17 medium+2% sucrose but that has a growth rate in M17 medium+2% glucose of zero or at least 0-50% reduced compared to the growth rate of the mother strain in M17 medium+2% glucose.

3. The method according to claim 1 , wherein the galactose-fermenting mother strain is selected from the group consisting of the Streptococcus thermophilus CHCC14994 strain that was deposited at Deutsche Sammlung von Mikroorganismen and Zellkulturen under accession no. DSM 25838, the Streptococcus thermophilus CHCC11976 strain that was deposited at Deutsche Sammlung von Mikroorganismen and Zellkulturen under accession no. DSM 22934, and strains derived therefrom.

4. A method according to claim 1 , wherein the obtained Streptococcus thermophilus strain increases the amount of glucose in 9.5% B-milk to at least 5 mg/ml when inoculated into the 9.5% B-milk at a concentration of 10 6 -10 7 CFU/ml and grown at 40° C. for 20 hours.

5. A method according to claim 1 , wherein the obtained Streptococcus thermophilus strain increases the amount of glucose in 9.5% B-milk with 0.05% sucrose to at least 5 mg/ml when inoculated into the 9.5% B-milk with 0.05% sucrose at a concentration of 10 6 -10 7 CFU/ml and grown at 40° C. for 20 hours.

Assignees

• Chr Hansen As

Inventors

• Johansen Eric
• Soerensen Kim Ib
• Curic-Bawden Mirjana
• Junge Mette Pia

Classifications

• C12N9/12

  transferring phosphorus containing groups, e.g. kinases (2.7) · CPC title

• C12N15/746

  for lactic acid bacteria (Streptococcus; Lactococcus; Lactobacillus; Pediococcus; Enterococcus; Leuconostoc; Propionibacterium; Bifidobacterium; Sporolactobacillus) · CPC title

• A23C19/0323

  using only lactic acid bacteria, e.g. Pediococcus and Leuconostoc species; Bifidobacteria; Microbial starters in general (using moulds A23C19/0682) · CPC title

• C12N15/1034

  Isolating an individual clone by screening libraries · CPC title

• A23C9/1238 Primary

  using specific L. bulgaricus or S. thermophilus microorganisms; using entrapped or encapsulated yoghurt bacteria; Physical or chemical treatment of L. bulgaricus or S. thermophilus cultures; Fermentation only with L. bulgaricus or only with S. thermophilus · CPC title