The processes of fermentation, accompanied by the growth and development of several species of microorganisms, are often accompanied by a change of some species of microorganisms for anothers , such a complex "behavior" of microorganisms during fermentation needs to be be deeply researched. The previously used approaches of evaluation of the type of interaction of particulate monocultures in consortiums make it possible to obtain only qualitative results (synergistic, antagonistic, additive interaction) generally, without taking into the consideration the change of this interaction during the cultivation. The purpose of the research was the development of a new approach of the quantitative determination of the parameter of the interaction of microorganisms of one species with another species expressed as a continuous function determined throughout the all fermentation period. In the process of the work a two-component consortium of lactic acid microorganisms Lactobacillus brevis and Lactobacillus plantarum was selected, cultivated in two different model media as part of a study of directed fermentation of vegetable products. The work the cultivation of monocultures (included in the studied consortium) was also carried out. The performed work the original approach was developed, the approach is based on a comparison of the growth rate of the microorganisms biomass of the consortium with the calculated additive dynamics. This approach is convenient to use to identify a complex regularity of changes of the types of interaction of microorganisms in the consortium in the form of a continuous function determined during the entire cultivation period. From the point of view of the synergies of the species of microorganisms entering the studied consortium in the active phase of fermentation, the "Slava" variety turned to be more profitable than the "Parus".

The regularity of the influence of the culture medium (substrate) on the development of microflora at the stage of preliminary fermentation of the model medium on the basis of white cabbage varieties "Parus" was studied. During the research, strains of lactic acid microorganisms Leuconostoc lactis were used. Step-by-step mathematical processing of the experimental data was carried out. Functional dependencies are obtained that most adequately approximate experimental data for modified (MMC) and basic (BMS) model media. Analysis of the experimental data showed that, depending on the type (composition) of the medium, the same species of microorganisms exhibit different dynamics of titer growth. In connection with this, an algorithm was developed to determine the optimal duration of pre-fermentation – «stop points». As a result of the research, it can be seen that the modification of the model medium with the addition of table salt and ascorbic acid to it promotes the formation of positive dynamics of the comparison indicator. This dynamics has three extremes, but only extremes are of practical significance, which were in the interval of the monotonic decrease of the titer. For successful development of the starting culture of the stage of the main fermentation, one of the conditions is a relatively small amount of the titer of the first culture at the end of the preliminary fermentation step to exclude competition. Thus, the position of the «stop-point» position corresponds to the period after the last peak of the comparison indicator. The investigated regularity of the effect of the preliminary cultivation of gram-positive microorganisms on the activity of lactic acid microorganisms in the process of fermentation is topical, since the whole process and the production of high-quality products fully depend on this approach.

Existing approaches for evaluation of types of interactions between individual monocultures in consortiums allow obtaining only qualitative results (synergistic, antagonistic, additive interaction) as a whole, without regarding to changes in the cultivation process. Therefore, the development of a new approach for the quantitative determination of this indicator as a continuous function defined during the all period of cultivation is in need. In the course of the research a two-component consortium of lactic acid microorganisms cultivated on different mediums according to directed fermentation process in vegetable products was chosen to analyze types of interaction. As a result, the an original approach that was based on comparison of grow speed of biomass of microorganisms with calculated additive curve determined by results of dynamic analysis of titre of microorganism participating in consortium in monoculture during their cultivation has been elaborated. This approach is a convenient tool to identify complex regularity in changes of types of microorganism interaction in consortium represented by continuous function defined during all cultivation period.

The aim of the research was to study the dynamics of active and titratable acidity with a low and high initial titer, while cultivating white head cabbage of the variety ‘Parus’ with lactic acid bacteria Leuconostoc lactis VKPM V-12150 and Leuconostoc mesenteroides subsp. mesenteroides VKPM V-8818 in the basic model medium (BMS) and the modified model medium (MMC) during fermentation . In this experiment, two important questions were considered: the creation of favorable conditions for the growth of lactic acid microorganisms and the suppression of undesirable pathogenic microflora, which can eventually lead to product spoilage. One of the key questions is to scale the results of studies related to the fermentation of plant objects by microorganisms on initially non-sterile raw materials that is the requirement to create as possible fast the conditions that restrain the reproduction of Cl. botulinum, preventing toxin accumulation in the product. Therefore, an important factor is the observance for the necessary boundary condition where for international standards, it reaches pH ≤ 4.6, and for Russian standards it reaches pH ≤ 4.2. Hence, an analysis of the experimental data showed that these boundary conditions were reached after the expiration of essentially different time intervals during the cultivation of microorganisms with different starting titers. As a result, it was shown with which lactic acid microorganisms the optimal parameters for the dynamics of active and titratable acidity were obtained, when the boundary condition reached pH 4.2. Since this value determines more "stringent" requirements for product safety. As a result of studies it was found that optimal parameters for the dynamics of active and titratable acidity when a limit pH value of 4.2 is obtained in the cultivation of lactic acid bacteria L. mesenteroides in the MMC, revealing that the value of the starting titer ranging from 3*103 to 3*105 CFU/g.