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

Patent metadata

Field	Value
Publication number	US-11044920-B2
Application number	US-201314396249-A
Country	US
Kind code	B2
Filing date	Apr 25, 2013
Priority date	Apr 25, 2012
Publication date	Jun 29, 2021
Grant date	Jun 29, 2021

Abstract

The dairy industry today faces a problem of providing an alternative to adding sweeteners to fermented milk products in order to achieve the desired sweet taste without the added calories. Furthermore, it would be highly advantageous to establish a method for reducing lactose in fermented milk products to a level which is acceptable for lactose-intolerant consumers. The above problems have been solved by providing mutant Streptococcus thermophilus strains and mutant Lactobacillus delbrueckii subsp. bulgaricus strains that excrete glucose to the milk when the milk is inoculated and fermented with such Streptococcus thermophilus strains and Lactobacillus delbrueckii subsp, bulgaricus strains. Thus, the present invention relates to strains of Streptococcus thermophilus and Lactobacillus delbrueckii subsp, bulgaricus which secrete glucose to the milk substrate during fermentation, as well as to mixed cultures comprising the Streptococcus thermophilus strains and the Lactobacillus delbrueckii subsp, bulgaricus strains, starter cultures comprising the strains and dairy products manufactured with the cultures. The present method also relates to use of the strains 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 producing a fermented milk product, comprising inoculating and fermenting a milk substrate with at least one mutant galactose-fermenting Streptococcus thermophilus strain obtained by a process 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 from the pool of 2-deoxyglucose resistant Streptococcus thermophilus strains as the mutant Streptococcus thermophilus strain, a strain that is able to grow to a colony when streaked on a plate with (i) M17 medium+2% lactose or M17 medium+2% galactose and (ii) 20 mM 2-deoxyglucose, and incubated at 40° C. for 20 hours,
wherein the mutant strain 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 as compared to the mother strain, and wherein the mutant strain (i) is resistant to 2-deoxyglucose, (ii) ferments lactose and/or excretes glucose when grown on a milk substrate, and (iii) is capable of acidifying milk to pH 5.

2. The method of claim 1 , wherein the mutant Streptococcus thermophilus strain carries a mutation in a gene encoding a component of a glucose/mannose phosphotransferase system, wherein the mutation inactivates the glucose/mannose phosphotransferase system or has a negative effect on expression of the gene.

3. The method of claim 2 , wherein the mutant Streptococcus thermophilus strain carries a mutation in the DNA sequence of the manM gene encoding the IIC Man protein of the glucose/mannose phosphotransferase system, wherein the mutation inactivates the IIC Man protein or has a negative effect on expression of the gene.

4. The method of claim 1 , wherein the mutant Streptococcus thermophilus strain is selected from the group consisting of the Streptococcus thermophilus strain CHCC15757 that was deposited at Deutsche Sammlung von Mikroorganismcn und Zellkulturen under accession No. DSM 25850, the Streptococcus thermophilus strain CHCC15887 that was deposited at Deutsche Sammlung von Mikroorganismen und Zellkulturen under accession No. DSM 25851, the Streptococcus thermophilus strain CHCC16404 that was deposited at Deutsche Sammlung von Mikroorganismen und Zellkulturen under accession No. DSM 26722, and a further mutant strain derived from any the deposited strains, wherein further the mutant strain is obtained by using one of the deposited strains as starting material, and wherein the further mutant strain retains the lactose fermenting property and/or the glucose secreting property of said deposited strain.

5. The method of claim 1 , further comprising using a Lactobacillus delbrueckii subsp. bulgaricus strain that is resistant to 2-deoxyglucose and that 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 at least 20 hours, to produce the fermented milk product.

6. The method of claim 1 , wherein the mutant Streptococcus thermophlius strain is selected from the Streptococcus thermophilus strain CHCC15757 that was deposited at Deutsche Sammlung von Mikroorganismen and Zellkulturen under accession No. DSM 25850, the Streptococcus therrnophilus strain CHCC15887 that was deposited at Deutsche Sanimlung von Mikroorganismen und Zellkulturen under accession No. DSM 25851, and the Streptococcus therinophilus strain CHCC16404 that was deposited at Deutsche Sammlung von Mikroorganismen und Zellkulturen under accession No. DSM 26722.

7. The method of claim 1 , wherein the mutant strain exhibits a higher growth rate in M17 medium+2% galactose than in M17 medium+2% glucose.

8. The method of claim 1 , Wherein the mutant strain has not been modified by recombinant DNA technology, and does not carry a mutation induced by any of chemical mutagens, UV-radiation and gamma radiation of the mother strain.

Assignees

• Chr Hansen As

Inventors

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

Classifications

• C12N15/01

  Preparation of mutants without inserting foreign genetic material therein; Screening processes therefor · CPC title

• C12N9/1205

  Phosphotransferases with an alcohol group as acceptor (2.7.1), e.g. protein kinases · 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

• C12N1/20 Primary

  Bacteria; Culture media therefor · 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