The growing consumer demand for the development of functional foods with a number of benefits for the consumer has led to a considerable increase in the studies focused on examining different natural agents to be included in the composition of newly developed functional foods. The chemical compositions of the essential oils (EOs) of lavender (Lavandula angustifolia Mill.), peppermint (Mentha piperita L.), raspberry seed (Rubus idaeus L.), and ylang-ylang (Cananga odorata (Lam.)) were determined using gas chromatography with a mass selective detector (GC-MS). The antibacterial and antifungal activities of these EOs were examined using a high-throughput 96-well microplate bioassay procedure and the MICs of each EO against each test microorganism were determined. The results indicated significant antimicrobial activity against Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 6538, Salmonella abony NTCC 6017, Pseudomonas aeruginosa NBIMCC 1390, Bacillus subtilis ATCC 19659, Penicillium chrysogenum ATCC 28089, Fusarium moniliforme ATCC 38932, Aspergillus niger ATCC 1015, and Aspergillus flavus ATCC 9643. To explore their potential applications in food preservation, model chocolate mousse food emulsions were prepared that incorporated EOs and/or selected probiotic lactobacilli strains in both free and encapsulated forms. The inclusion of EOs and/or probiotic lactobacilli resulted in enhanced microbial safety and an extended shelf life. Furthermore, the chocolate mousse variants that were biopreserved with the inclusion of probiotic lactobacilli maintained a high viable lactobacillus cell concentration throughout the storage period. As a result, these products would not only be suitable as functional probiotic foods but also as effective delivery vehicles for probiotic lactobacilli.

Species identification is the first step in the examination of newly isolated microorganism strains, including the cases when they are intended for application in the development of probiotic preparations or starters for different food products. The thorough identification process of newly isolated strains combines the application of different physiological, biochemical, and molecular genetic methods. The aim of the present study was to identify the species-level lactic acid bacteria (LAB) strains isolated from spontaneously fermented sourdoughs prepared from different flour types: Khorosan wheat, wheat, barley, buckwheat, spelled, spelt, and corn. Both classical phenotypic (cellular morphology characterization, and API 50 CHL) and molecular genetic methods (RAPD, ARDRA-analysis, 16S rDNA sequencing, and species-specific PCR) were applied. It was found that cultures with a short-rod morphology predominated among the 30 sourdough isolates. According to the RAPD profiles obtained, the isolates were divided into nine genotypes corresponding to nine genetically distinct strains. It was determined that individual sourdoughs made with different flour types shared cultures with a common genotype. The analysis of the physiological and biochemical profiles of the LAB isolates performed with the API 50 CHL system divided them into two groups according to their identification: Lactiplantibacillus plantarum (Lp. plantarum) 1 and Levilactobacillus brevis (Lv. brevis) 3. According to the 16S rDNA restriction profile, the LAB isolates showed two profiles corresponding to the Lp. plantarum and Lv. brevis groups. 16S rDNA sequencing and a comparison of the partially read 16S rDNA sequences of the studied isolates confirmed that some of them belonged to the Lv. Brevis species, but did not provide sufficient evidence that the rest of the cultures belonged to the Lp. Plantarum species. The species-specific PCR clearly separated the isolates from the Lp. plantarum group into two groups: isolates of the Lp. plantarum species and isolates of the Lp. paraplantarum species. The summary of the results of the conducted polyphasic taxonomic study determined the investigated LAB strains isolated from spontaneously fermented sourdoughs as representatives of the Lv. brevis, Lp. plantarum ssp. paraplantarum, and Lp. paraplantarum species.

In order for a strain to be considered a probiotic or suitable plant bioprotective agent, it must have proven antimicrobial activity against pathogenic bacteria and phytopathogenic fungi. Bacillus amyloliquefaciens M exhibited significantly high antifungal activity against pathogenic fungi of the genera Aspergillus, Penicillium, Fusarium, and Sclerotinia; yeasts of the genera Candida and Saccharomyces; as well as high antibacterial activity against pathogens of the genera Escherichia, Salmonella, Staphylococcus, Listeria, Pseudomonas, and Bacillus. The manifested antimicrobial activity was influenced by the composition of the growth medium. The antifungal activity of the strain was investigated at growth temperatures of 30 °C and 37 °C, and at different pH values in aerobic and anaerobic cultivation, under static and dynamic culturing conditions. High antifungal activity was observed at the 24th h on both growth media (LBG broth and MPB broth) at pH = 6 and pH = 7 in aerobic and anaerobic cultivation. Bacillus amyloliquefaciens M produced antibiotic substances at pH > 5.0, and the antibiotic substances were either secreted into the medium or associated with the cell surface. Four compounds with different antifungal activity and different R_f values were registered through thin-layer chromatography (R_f1 = 0.47; R_f2 = 0.55; R_f3 = 0.67; and R_f4 = 0.75), two of the compounds were ninhydrin-positive. Bacillus amyloliquefaciens M was cultured in a bioreactor with stirring, and the parameters of the growth kinetics and the sporulation kinetics have been modeled. A spore concentrate of Bacillus amyloliquefaciens M has been obtained. In further research, the efficiency of the concentrate as a plant bioactive agent will be tested.

Probiotic bacteria are used for food biopreservation because their metabolic products might contribute to ensuring food microbiological safety and/or increase its shelf life without the addition of chemical preservatives. Moreover, biopreserved foods are excellent vehicles for the delivery of probiotic bacteria. The aim of the study was to investigate the potential of chocolate mousse food matrix for the delivery of the probiotic strain Lactobacillus helveticus 2/20 (Lb. helveticus 2/20) and to investigate its capacity to inhibit the growth of two foodborne pathogenic bacteria (Staphylococcus aureus and Escherichia coli). Therefore, the populations of free or encapsulated in calcium alginate Lb. helveticus 2/20 cells and/or of each pathogen (used to voluntarily contaminate each sample) were monitored both in complex nutrient medium (MRS broth) and in chocolate mousse under refrigeration conditions and at room temperature. Lb. helveticus 2/20 alone in free or encapsulated state effectively inhibited the growth of Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923 in chocolate mousse when stored at 20 ± 2 °C. Practically no viable unwanted bacteria were identified on the 7th day from the beginning of the process. High viable Lb. helveticus 2/20 cell populations were maintained during storage under refrigerated conditions (4 ± 2 °C) and at room temperature. Chocolate mousse is thus a promising food matrix to deliver probiotic Lb. helveticus 2/20 cells, which could also protect it from contamination by unwanted bacteria.