Bacterium

• US 9,060,524 B2
• Filed: 09/29/2014
• Issued: 06/23/2015
• Est. Priority Date: 01/28/2010
• Status: Active Grant

• Current Assignee: CHR Hansen Holding A/S
• Original Assignee: CHR Hansen Holding A/S
• Inventors: Janzen, Thomas, Christiansen, Ditte Ellegaard
• Primary Examiner(s): Monshipouri, Maryam
• Application Number:
  US14/500,134
• Publication Number:
  US 20150099273A1
• Time in Patent Office: 267 Days
• US Class Current: 1/1
• CPC Class Codes: A23C 2220/202 Genetic engineering of microorganisms used in dairy technology
• CPC Class Codes: A23C 9/1209 Proteolytic or milk coagulating enzymes, e.g. trypsine
• CPC Class Codes: A23C 9/123 using only microorganisms of the genus lactobacteriaceae; Yoghurt A23C9/13 takes precedence
• CPC Class Codes: A23C 9/1238 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 Class Codes: A23V 2400/11 Lactobacillus
• CPC Class Codes: A23V 2400/123 Bulgaricus
• CPC Class Codes: A23V 2400/143 Fermentum
• CPC Class Codes: A23V 2400/249 Thermophilus
• CPC Class Codes: C12N 1/20 Bacteria; Culture media therefor
• CPC Class Codes: C12N 1/205 Bacterial isolates
• CPC Class Codes: C12N 15/01 Preparation of mutants without inserting foreign genetic material therein; Screening processes therefor
• CPC Class Codes: C12N 15/746 for lactic acid bacteria (Streptococcus; Lactococcus; Lactobacillus; Pediococcus; Enterococcus; Leuconostoc; Propionibacterium; Bifidobacterium; Sporolactobacillus)
• CPC Class Codes: C12N 9/1205 Phosphotransferases with an alcohol group as acceptor (2.7.1), e.g. protein kinases
• CPC Class Codes: C12Q 1/14 Streptococcus; Staphylococcus
• CPC Class Codes: C12R 2001/225 Lactobacillus
• CPC Class Codes: C12R 2001/46 Streptococcus ; Enterococcus; Lactococcus
• CPC Class Codes: C12Y 207/01006 Galactokinase (2.7.1.6)

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.

Claims

1. A method for manufacturing a lactic acid bacterium that generates higher shear stress and/or gel stiffness than its mother strain when the bacterium is used for fermenting milk, comprising:

(a) providing a lactic acid bacterial strain as the mother strain;

(b) exposing the lactic acid bacterial strain to a bacteriophage which is able to lyse the mother strain;

(c) optionally, before during, or after step (b), introducing into the lactic acid bacterial strain a mutation in the galK gene or a galK regulatory sequence; and

(d) subsequently isolating the bacterial strain, wherein the isolated strain (i) is resistant against more phages than the mother strain and (ii) has a mutation in a galK gene or a galK regulatory sequence relative to the mother strain.

2. The method of claim 1, wherein the bacteriophage is selected from the group consisting of CHPC658 (DSM 23961), CHPC1057 (DSM 23962), CHPC1089 (DSM 24022) and CHPC1152 (DSM 23994).

3. The method of claim 1, wherein step (c) is carried out.

4. The method of claim 1, wherein the isolated bacterial strain has a mutation in the promoter region of the galK gene relative to the mother strain.

5. The method of claim 4, wherein the isolated bacterial strain has a mutation in the −

10 region (the Pribnow box) or in the region between the Pribnow box and the ribosome binding site of the galK gene relative to the mother strain.

6. The method of claim 5, wherein the isolated bacterial strain has a mutation that comprises one or more selected from the group consisting of:

the replacement of one or more nucleotides in the region between the Pribnow box and the ribosome binding site of the galK gene relative to the mother strain;

the replacement of one or both of C and G in the wildtype −

10 region (TACGAT, SEQ ID NO;

7) with a nucleotide independently selected from the group consisting of A and T;

the replacement of C in the wildtype −

10 region (TACGAT, SEQ ID NO;

7) with a nucleotide independently selected from the group consisting of A and T;

the replacement of C in the wildtype −

10 region (TACGAT, SEQ ID NO;

7) with T; and

a −

10 region which has the nucleotide sequence TATGAT (SEQ ID NO;

8), TATTAT (SEQ ID NO;

9) or TACTAT (SEQ ID NO;

10).

7. The method of claim 1, wherein the mutation in the isolated bacterial strain comprises the replacement of C in the sequence TTCAGT (SEQ ID NO:

6) downstream from the wildtype Pribnow box with a nucleotide selected from the group consisting of A, T and G.

8. The method of claim 1, further comprising one or more step(s) selected from the group consisting of:

(c1) screening for a mutant strain having increased phage resistance compared to the mother stain; and

(c2) screening for a mutant strain having increased galactose degrading activity compared to the mother stain.