International scientific-online conference STUDY OF ANTIMICROBIAL METABOLITES OF LACTIC ACID BACTERIA. Khadjimetova Sevara Raupovna

Аннотация

In the past decades, detailed studies of SAB have revealed their ability to produce antimicrobial substances of various natures.Many SAB strains, in addition to lactic acid, produce a large number of non-specific low molecular weight compounds, such as organic acids, hydrogen peroxide, diacetyl, reuterin, etc., which determine the spectrum of their antimicrobial action.Many SAB strains, in addition to lactic acid, produce a large number of non-specific low molecular weight compounds, such as organic acids, hydrogen peroxide, diacetyl, reuterin, etc., which determine the spectrum of their antimicrobial action.As mentioned above, the main final metabolites produced by SAB during fermentation are lactic and acetic acids.Acetic acid has a broader antimicrobial activity than lactic acid. However, a synergistic effect is known for both acids: A mixture of acetic and lactic acids inhibits the growth of pathogenic gram- negative enterobacteria Salmonella typhimurium.It is noted that L-lactate has a greater inhibitory effect than the D-isomer. Different microorganisms react differently.Depending on the acidity of the environment, for example, at a pH below 5.0, lactic acid inhibits the development of spore-forming bacteria, but does not affect the development of microscopic fungi and yeasts. Keywords: Lactobacillus, strain, probiotic, SAB, isolation, antibacterial activity. Introduction. The search for new promising probiotic strains, the identification of their probiotic properties, as well as the study of already known probiotic strains are important tasks of basic science.Research aimed at isolating and studying new strains of SABs is a widespread and urgent issue worldwide.One of the first and most important steps in the search and selection of a promising strain is to determine its taxonomy, which allows us to have a preliminary understanding of the safety, origin, habitat, and physiological characteristics of a microorganism, correctly isolating the strain at the species level.Lactobacteria are one of the most studied representatives of the SAB group, along with streptococci, lactococci, and enterococci.According to the modern phylogenetic classification of bacteria, the genus Lactobacillus has more than one hundred and fifty species and subspecies.Using 16S rRNA gene sequencing, 126 THEORETICAL ASPECTS IN THE FORMATION OF PEDAGOGICAL SCIENCES International scientific-online conference the researchers identified 14 isolates of SABs as: Enterococcus mediterraneensis, Lactobacillus fermentum, and Streptococcus lutetiensis. They studied the probiotic properties of the isolates.The authors' work investigated the antibacterial activity and probiotic properties of Lactobacillus spp., which strains were sensitive to ampicillin. Literature Analysis And Methodology. Dairy products were used to isolate SAB isolates.Enriched MRS-nutrient medium (Hi-Media, India) was prepared, homogenized in sterile saline (0.85%, pH 7).The homogenate was diluted to 10-5 and inoculated into 2 Petri dishes containing MRS-agar medium and incubated under anaerobic and aerobic conditions for 24-48 hours at 37- 40°C.The isolated isolates were characterized according to their morphological, cultural, physiological, and biochemical properties according to the indicators specified in the "Bergji spectrometer".Samples with rod-shaped and blue cells under the microscope, Gram-negative and catalase-negative, were selected and cultured on MRS-broth medium (HiMedia, India). Discussion. The following composition was used to prepare the nutrient medium for the isolation of SAB isolates: MRS-broth nutrient medium composition (g\l); peptone -10,0; meat extract -10,0; yeast extract -5,0; twin 80-1,0 ml; sodium salt of acetic acid -5,0; ammonium citrate - 2,0; glucose -20; MgSO x 7H O -0.2; 4 2 MnSO x 4H O -0,05; 4 2 L-cysteine -0,2; рН- 6,2-6,5., 15 for a minute 121 °С sterilized in an autoclave at a temperature of 1 atm. MRS- agar medium composition (g\l); peptone -10,0; meat extract -10,0; yeast extract -5,0; twin 80-1,0 ml; sodium salt of acetic acid -5,0; 127 THEORETICAL ASPECTS IN THE FORMATION OF PEDAGOGICAL SCIENCES International scientific-online conference ammonium citrate - 2,0; glucose -20; MgSO x 7H O -0.2; 4 2 MnSO x 4H O -0,05; 4 2 L-cysteine -0,2; agar-agar-18; рН- 6,2-6,5., 15 for a minute 121 °С sterilized in an autoclave at a temperature of 1 atm. Composition of MRS-1 medium without added carbohydrates, (100 ml); peptone - 1 g; meat extract - 0,5 g; ammonium salt of citric acid - 0,2 g; sodium salt of acetic acid - 0,5 g; К НРО - 0,2 g; 2 4 MgSO -0,02 g; 4 MnS0 - 0,005 g; 4 Тvin 80-0,1ml; рН 6,8-7,0. Bromcresol purple (Reakhim, Russia) served as an indicator (1.4 ml of a 1.6% alcohol solution is added to 1 liter of medium). This indicator changes its initial purple color to yellow under the influence of acidic products formed when carbohydrates are broken down by lactobacteria. The prepared MRS-1 medium without added carbohydrates is plac