Electra Stylianopoulou

Seven wild-type lactic acid bacteria, belonging to Lactiplantibacillus plantarum and Lactococcus cremoris species, were isolated from beetroots and white mushrooms and evaluated for their safety and functional profile. Lc. cremoris isolates were sensitive to all antibiotics tested, while L. plantarum strains exhibited resistance in certain antibiotics. Among them, Lc. cremoris FBMS_5810 showed the highest cholesterol removal ability (51.89%) and adhesion capacity to Caco-2 cell lines (32.14%), while all plant origin strains exhibited strong antagonistic and inhibitory activity against foodborne pathogens, as well as high survival potential during an in vitro digestion model. Subsequently, freeze-dried immobilized Lc. cremoris FBMS_5810 cells on oat flakes were prepared with initial cell loads >8.5 log CFU/g, and the effect of trehalose as a cryoprotectant in cell viability during storage at room and refrigerated temperatures for up to 180 days was studied. A significant reduction in cell loads was observed in all cases studied. However, freeze-dried immobilized Lc. cremoris FBMS_5810 cells on oat flakes prepared using trehalose as a cryoprotectant stored at 4 °C exhibited the highest cell viability (8.75 log CFU/g) after 180 days. In the next step, functional breakfast cereals enriched with freeze-dried immobilized Lc. cremoris FBMS_5810 cells on oat flakes (produced with (MLT) or without (ML) trehalose) were developed and stored at room and refrigerated temperatures for 180 days. The initial cell levels ≥ 9.18 log CFU/g were achieved, while a significant decrease was recorded during storage in all cases. The maintenance of cell loads ≥ 7.75 log CFU/g was documented in the case of both ML and MLT samples stored at 4 °C; however, the presence of trehalose in MLT samples resulted in cell viability 7.52 log CFU/g after 180 days of storage at room temperature. Importantly, the functional breakfast cereals were accepted by the panel during the sensory evaluation.

Raw goat and ewe’s milk samples were used for the isolation of seven lactic acid bacteria new strains. After testing hemolytic activity and resistance to antibiotics, specific functional properties were evaluated; Lactococcus lactis subsp. lactis FBM_1321 and Lacticaseibacillus paracasei FBM_1327 strains resulted in the highest cholesterol assimilation percentages ranging from 28.78 to 30.56%. In addition, strong adhesion capacity to differentiated Caco-2 cells (1.77–21.04%) was mapped, and the lactobacilli strains exhibited strong antagonistic activity against foodborne pathogens compared to lactococci. The strains were able to grow at low pH and high NaCl concentrations, conditions that prevail in food systems (cell counts ranged from 1.77 to 8.48 log CFU/mL after exposure to pH 3 and from 5.66 to 9.52 log CFU/mL after exposure to NaCl concentrations up to 8%). As a next step, freeze-dried immobilized Lc. paracasei FBM_1327 cells on oat flakes were used for the preparation of functional yoghurt and ayran products. Cell loads of the functional strain remained high and stable in both products (7.69 log CFU/g in yoghurt and 8.56 log CFU/g in ayran after 30 days of storage at 4 °C) throughout their shelf life. No significant changes in the volatile profile were noticed, and the new products were accepted by the panel during the sensory evaluation.

As the food and pharmaceutical industry is continuously seeking new probiotic strains with unique health properties, the aim of the present study was to determine the impact of short-term dietary intervention with novel wild-type strains, isolated from various sources, on high-fat diet (HFD)-induced insulin resistance. Initially, the strains were evaluated in vitro for their ability to survive in simulated gastrointestinal (GI) conditions, for adhesion to Caco-2 cells, for bile salt hydrolase secretion, for cholesterol-lowering and cellular cholesterol-binding ability, and for growth inhibition of food-borne pathogens. In addition, safety criteria were assessed, including hemolytic activity and susceptibility to antibiotics. The in vivo test on insulin resistance showed that mice receiving the HFD supplemented with Pediococcus acidilactici SK (isolated from human feces) or P. acidilactici OLS3-1 strain (isolated from olive fruit) exhibited significantly improved insulin resistance compared to HFD-fed mice or to the normal diet (ND)-fed group.