Lactic bacterium for texturizing food products selected on the basis of phage resistance

Abstract

The present invention relates to a bacterial cell with texturizing property, starter cultures comprising the cell, and dairy products fermented with the starter culture.

1 .- 48 . (canceled) 
     
     
         49 . A method for manufacturing a lactic acid bacterium (LAB) having a mutation in the −10 region of a galactokinase (GalK) gene, comprising:
 producing, from a mother LAB strain, a mutant LAB strain having a mutation in the −10 region of the GalK gene, and then 
 selecting the mutant LAB strain, 
 wherein the mutant LAB strain (i) exhibits enhanced galactose-degrading activity during milk fermentation as compared the mother LAB strain and (ii) produces milk that has a higher viscosity than milk produced with the mother LAB strain under comparable conditions. 
 
     
     
         50 . The method of  claim 49 , wherein the mother LAB strain has a GalK gene with the nucleotide sequence TACGAT (SEQ ID NO: 7) in the −10 region. 
     
     
         51 . The method of  claim 50 , wherein the method results in the replacement of one or both of C and G in the TACGAT sequence of the mother LAB strain with a nucleotide independently selected from A and T. 
     
     
         52 . The method of  claim 49 , wherein the mutant LAB strain has a GalK gene with a nucleotide sequence selected from TATGAT (SEQ ID NO:8), TATTAT (SEQ ID NO:9), and TACTAT (SEQ ID NO:10) in the −10 region. 
     
     
         53 . The method of  claim 49 , wherein the mutant LAB strain is a  Streptococcus thermophilus  strain. 
     
     
         54 . The method of  claim 49 , wherein the mutant LAB strain is produced by a method comprising one or more of genetic engineering, radiation treatment, and chemical treatment. 
     
     
         55 . A LAB which is obtained by the method of  claim 49 . 
     
     
         56 . A mutated lactic acid bacterium (LAB) having a galactokinase (GalK) gene with a nucleotide sequence selected from TATGAT (SEQ ID NO:8), TATTAT (SEQ ID NO:9), and TACTAT (SEQ ID NO:10) in the −10 region. 
     
     
         57 . The mutated LAB of  claim 56 , wherein the LAB is a  Streptococcus thermophilus  bacterium. 
     
     
         58 . The mutated LAB of  claim 57 , wherein the  Streptococcus thermophilus  bacterium is selected from CHCC11379 (DSM 22884), CHCC11342 (DSM 22932), CHCC11976 (DSM22934), and functionally equivalent mutants of any of these. 
     
     
         59 . A composition comprising the LAB of  claim 56 . 
     
     
         60 . The composition of  claim 59 , wherein the composition further comprises one or more additional LAB strains selected from Lactobacillus bulgaricus strains,  Lactobacillus johnsonii  strains, and  Lactobacillus fermentum  strains. 
     
     
         61 . The composition of  claim 60 , wherein the additional LAB strain produces a polysaccharide and/or a fructosyl transferase enzyme. 
     
     
         62 . The composition of  claim 60 , wherein the composition comprises at least 10 10  cell forming units (CFU) of the additional LAB strain and at least 10 10  CFU of the mutated LAB. 
     
     
         63 . A dairy product produced by a method comprising:
 adding the mutated LAB strain of  claim 56  to a milk substrate, and then   fermenting the milk substrate.   
     
     
         64 . A dairy product comprising the mutated LAB of  claim 56 . 
     
     
         65 . The dairy product of  claim 64 , wherein the dairy product is selected from yoghurt, milk, and cheese. 
     
     
         66 . The dairy product of  claim 64 , wherein the dairy product is selected from a stirred-type product, a set-type product, and a drinkable product. 
     
     
         67 . The dairy product of  claim 64 , wherein the dairy product further comprises one or more ingredients selected from a fruit concentrate, a syrup, a probiotic bacterial culture, a coloring agent, a thickening agent, a flavoring agent, and a preserving agent. 
     
     
         68 . The dairy product of  claim 64 , wherein the dairy product has a viscosity of more than 100 Pa, measured as shear stress at 300 s −1 . 
     
     
         69 . A dairy product produced by a method that comprises:
 fermenting a milk or dairy substrate with (i) a  Streptococcus thermophilus  bacterium comprising a galactokinase (GalK) gene having a −10 region having a nucleotide sequence selected from the group consisting of TATGAT (SEQ ID NO:8), TATTAT (SEQ ID NO:9) and TACTAT (SEQ ID NO:10) and (ii) a  Lactobacillus delbrueckii  ssp.  bulgaricus  bacterium.