Development of Lactic acid Microorganisms during Fermentation of Substrate with an Increased Concentration of Carbohydrates

Abstract

Introduction. Creating favorable conditions for the development of lactic acid microorganisms is one of the main factors in obtaining high-quality fermented products. The cycle of their life directly depends on the amount and composition of carbohydrates in plant tissue. Since a significant part of carbohydrates is consumed at the initial stage of fermentation process, additional fortification is needed. The research objective was to study the development rate of lactic acid microorganisms during the fermentation of plant substrate with a modified carbohydrate composition. Study objects and methods. The research featured model medium based on white cabbage of the Parus variety. The medium was fermented with different strains of lactic acid microorganisms: at the first stage of fermentation – Leuconostoc mesenteroides, at the second stage – Lactobacillus casei VKM 536, Lactobacillus plantarum VKM B-578, Lactobacillus brevis VKM B-1309, and their paired consortia. The initial plant material was subjected to grinding and removal of native microflora for the development of target lactic acid microorganisms, then inoculated with L. mesenteroides. The target lactic acid microorganisms were introduced after the first stage of fermentation with simultaneous adjustment of the carbohydrate composition. Results and discussion. The technology included modes of controlled two-stage microbial transformation of plant raw materials using modification of the carbohydrate composition of the substrate. A number of experiments made it possible to select the optimal composition of the consortium and establish the optimal fermentation time at the main stage of microbial processing. When the plant substrate was fermented by the consortium of L. casei + L. plantarum with an increased carbohydrate component, the decrease in the concentration was quite small: after 5–30 days, the decrease in the concentration of microorganisms did not exceed one order of magnitude, which was insignificant at an initial concentration of eight orders of magnitude. In other consortia, the decrease in the concentration of microorganisms was more pronounced. Conclusion. The fortification of the vegetable substrate with carbohydrates made it possible to maintain the concentration of lactic acid microorganisms at a level comparable to the concentration at the time of inoculation. The concentrations of microorganisms varied slightly in both monocultures and their paired consortia during the entire main fermentation stage of the model medium with a modified carbohydrate component. By the end of the main fermentation stage, the concentration of microorganisms did not fall below 107 CFU/g. Therefore, the resulting system “microflora – substrate” proved to have probiotic properties. The study can be used to develop new technological modes of controlled step-by-step fermentation of plant raw materials in order to improve the quality indicators of the final product.