RU2590716C1 - Strain of bacteria streptococcus thermophilus strain used for preparation of cultured milk product - Google Patents

Abstract

FIELD: food industry.

SUBSTANCE: invention relates to microbiological and food industry and concerns a lactic acid bacteria Streptococcus thermophilus. Said bacteria are used as starter when producing fermented milk products usually combined with cultures of Lactobacillus bulgaricus. Streptococcus thermophilus strain No. 7c-UV is deposited in Departmental collection of microorganisms GNU ARRIAM for agricultural purposes, No. RCAM 02910 has optimal biotechnological properties: high growth rate, high level of accumulation of biomass in period of logarithmic stage and during limitation of cell population growth.

EFFECT: pure culture of lactic acid bacteria strain Streptococcus thermophilus with a number of useful properties can be used as a producer preparations-eubiotics and cultured milk medical and preventive food products.

1 cl, 3 tbl, 2 ex

Description

The invention relates to the microbiological and food industries, and relates to lactic acid bacteria (ICD), in particular Streptococcus thermophilus, which are used as starter culture to produce fermented milk products, including yoghurts, usually in combination with Bulgarian stick cultures. The maximum growth rate of S. thermophilus cells in milk, tested by the rate of fermentation, the ability to form viscous clots, low acidity is often decisive when choosing strains for starter culture [1]. The level of biomass accumulation is determined by the number of cells formed during the logarithmic stage. At the end of the logarithmic stage, a period of limitation of the growth of the cell population begins in connection with the increasing density of the cell mass and an increase in the acidity of the medium.

Closest to the invention in technical essence and the achieved positive effect is a production strain of S. thermophilus ST 18 [3]. It has two phases of the logarithmic growth stage in milk, including the stage of growth limitation, is close to 10 ⁹ cells / ml and does not exceed this value during further incubation.

In contrast to the prototype, the bacterial strain S. thermophilus 7c-UV has increased viability in conditions of deficiency of nutrient components of the medium, a high level of biomass accumulation (more than 10 ⁹ cells / ml) after 24 hours of incubation in milk and resistance to acidification to pH 5, 0 at the stage of logarithmic growth.

The strain was isolated from collection samples by direct seeding on liquid nutrient media, followed by seeding on agarized media and deposited in the Departmental collection of beneficial microorganisms for agricultural purposes (VKSM) GNU VNIISKHM under the number RCAM 02910.

The strain S. thermophilus 7c-UV has the following characteristics:

Morphology. Gram-positive bacteria, indisputable, motionless, oval-shaped cells that form pairs or chains of up to five cocci. On the surface of agarized media forms a white, convex, smooth with smooth edges, milky colonies with a diameter of up to 2 mm.

Cultural signs. In meat and peptone broth with 2.5% sodium chloride, growth is observed, and with 4% and 6.5% sodium chloride, there is no growth; on enterococcal agar, the strain grows in the form of pale pink colonies; there is no growth on agar with 0.04% potassium tellurite, it grows in the milk hydrolyzate with a pH of 9.2, and there is no growth at a pH of 9.6 (Table 1).

In order to study the affiliation of the selected strain to serological groups according to Lansfield, a latex agglutination reaction was carried out with specific sera of groups B, C, F, G, D. Streptococcus thermophilus 7c-UV was agglutinated with all antigens.

Physiological and biochemical properties. The acid is formed by a strain of fructose, glucose, mannose and lactose. Arabinose, rhamnose, xylose, dextran, inulin, salicin, starch are not fermented.

Milk coagulates within 18 hours. Optional anaerobic, type of fermentation - homoenzymatic. The optimum growth temperature is 37 ° C. Acidity 76 ° T. The number of colony forming units per gram of test material (CFU / g) is greater than 1 · 10 ⁹ CFU / g.

Maintaining the strain.

Storage methods: the culture is stored in a lyophilized state in ampoules at a temperature of - 4 ± 2 ° C, in a liquid or agarized nutrient medium at 5-6 ° C.

Storage media: MPA, MRS under mineral oil; the culture remains viable up to 3 years at low positive temperatures and up to 6 months at room temperature

Cultivation medium: cow's milk, whole, normalized or skimmed.

Incubation time: 5-7 hours, depending on the incubation temperature, the amount of yeast introduced into milk 1.5-2%, the frequency of reseeding 1 time per month (table. 2).

Example 1. Growth characteristics of the claimed strain

50 μl seed, representing a bacterial culture grown at 37 ° C in 3 ml of 0.5% milk, was seeded in tubes containing 3 ml of the same milk to a final concentration of 10 ⁶ cells / ml and incubated at 37 ° C. Accounting for the titer of cells was done after 3.5 and 4.5 hours of incubation (table. 3). The cell titer was determined by counting the number of colonies grown 24 hours after plating the bacterial suspension on Petri dishes with MPA medium. The level of biomass accumulation by Streptococcus thermophilus 7c-UV strain after 24 hours of incubation in milk under the same conditions is 1.9 × 10 ⁹ cells / ml, which exceeds the value of this parameter for the closest analogues - production strains of S. thermophilus VKPM 9589 [4] and S. thermophilus strain VKPM 9588 [5]. The level of biomass accumulation by VKPM 9588 strain under the same conditions is 9.4 × 10 ⁸ , and VKPM 9589 is 1.0 × 10 ⁹

Example 2. The study of the influence of liquid culture of strain Streptococcus thermophilus No. 7c-UV on intestinal biocenosis

The quantitative and qualitative composition of the intestinal microflora of the Smena cross chickens (according to V. Znamensky, 1986), the microflora stability index was determined on the 0, 15, 30, and 45 days of the experiment. Prior to the use of Streptococcus thermophilus strain No. 7c-UV, 42% of E. coli, 35% of bifidobacteria and 23% of lactobacilli were isolated from the feces of cross-country chickens. The number of lactobacilli statistically significantly increased in the chickens of the experimental group of the Cross at 15 days age relative to the control, by 15.9%, the number of E. coli decreased by 11.3%, the number of bifidobacteria did not differ from that in the chickens of the control group. At the age of 30 days in the chickens of the experimental group, the number of lactobacilli was 14.5% higher than the analogues from the control, the number of E. coli was lower by 4.2% (P <0.05). At the age of 45 days, in the chickens of the experimental group, the number of lactobacilli was higher by 12.1 (P <0.1), E. coli was lower by 12.4% (P <0.05). The microflora stability index was higher in chickens of the experimental group by 13.8%. Therefore, the strain Streptococcus thermophilus No. 7c-UV accelerates the process of colonization of the intestine with beneficial microflora and qualitative changes in the microbial landscape in the intestine. Preservation of a normal intestinal biocenosis is observed even after the termination of the use of leaven.

Information sources

1. Stepanenko P.P. Microbiology of milk and dairy products. 1999 .-- 415 p.

2. The determinant of bacteria Bergey: Ref. Publishing House: Per. from English: in 2 vol. T. 2 / Ed. J. Hoult et al. - 9th ed. - M.: Mir, 1997 .-- S. 565

3. Letort. C. Casein utilization by Streptoccocus thermophilus results in diauxic growth in milk // J. Appl. Environ. Microbiol., 2002 Jun. - V. 68. - P. 3162-3165.

4. RF patent No. 2218793. Method for the production of yogurt / Artyukhov S.I., Zaika N.A. RF // Decl. 07/31/2001; publ. 12/20/2003. Bull. Number 35.

5. RF patent No. 2109455. Composition for the production of fermented milk product and method for its production / Zobkova Z.S. // Declared 06/14/1996; publ. 04/27/1998. Bull. Number 22.

Claims (1)

The bacterial strain Streptococcus thermophilus, deposited in the Departmental collection of beneficial microorganisms for agricultural purposes, GNU VNIISKhM under registration number RCAM02910, is a component of the bacterial starter culture for the preparation of fermented milk dietetic products with a high growth rate, a high level of biomass accumulation during the logarithmic stage and during cell growth limitation populations.