Isolation and Identification of Lactococcus lactis and Weissella cibaria Strains from Fermented Beetroot and an Investigation of Their Properties as Potential Starter Cultures and Probiotics

Abstract

The presence of certain microorganisms in dairy products or silage is highly desirable. Among them are probiotic strains of lactic acid bacteria (LAB), which show many beneficial features, including antimicrobial properties that support the development of beneficial microflora; in addition, owing to their biochemical activity, they influence the nutritional, dietary, and organoleptic properties of food products. Before being placed on the market, each strain requires separate testing to determine its probiotic properties and effectiveness. The aim of this study was to isolate LAB strains from a pickled beetroot sample that could be used in the dairy industry and with the potential to be considered as a probiotic in the future. Two strains identified using the MALDI technique were selected-Lactococcus lactis and Weissella cibaria. The optimal growth conditions of the strains were determined, and their proteolytic properties were assessed with the use of the o-PA reagent and spectrophotometry. The lipid profile was analyzed using the SALDI (surface-assisted laser desorption/ionization) technique and silver nanoparticles. High-performance liquid chromatography was used to assess the ability of the strains to synthesize beneficial metabolites, such as B vitamins (B2, B3, and B9) or lactic acid, and gas chromatography was used to analyze the substances responsible for organoleptic properties. Moreover, the ability to inhibit the growth of pathogenic strains was also tested in the selected strains. Both tested strains demonstrated the desired properties of starter cultures for future use in functional food production, showing that fermented plant products can serve as valuable potential probiotic sources.

Keywords: B vitamins; lactic acid bacteria; laser desorption/ionization; metabolites.

Figure 1

Optical microscope photos of the Gram staining of the tested strains: (A)—Lactococcus lactis; (B)—Weissella cibaria.

Figure 2

Graphs showing the growth of the tested LAB strains in various culture media and temperatures.

Figure 3

Calibration curve showing the dependence of absorbance on the concentration of glycine.

Figure 4

GC/MS chromatograms of control sample (MRS agar) and analyzed LAB strain samples.

Figure 5

Exemplary chromatograms obtained during the analysis of selected compounds by HPLC. L—lactose; LA—lactic acid; B2—riboflavin; B3—niacin; B9—folic acid; tR—retention time.