Several mechanism and non-mechanism-based studies supporting the claim that lactic acid bacteria (LAB) strains confer health benefits and play immune-modulatory roles were examined in this review. Probiotic applications of LAB on global burdens such as obesity and type-2 diabetes were discussed as well as the use of yoghurt and ice cream as important vehicles to convey several beneficial LAB strains. Probiotic and symbiotic dairy products may be used in the nearest future to treat a variety of health disorders. Current studies suggest that lactic acid bacteria possess anti-obesity and anti-diabetic propensities on their hosts and thus can play a crucial role in human health care. Research in the rheological and physicochemical properties of ice cream as well as its applications are also on the increase. These applications face certain hurdles including technological (for less developed countries), consumer acceptability of new functional foods may be influenced by culture, ethics or religion. There is need for more studies on the genetic basis for probiotic properties which will give further understanding regarding novel manipulation skills and applicability in nutrition and health sectors. More studies confirming the direct effects of probiotic LABs in lowering the spread of food-borne and other pathogens are also anticipated.

Aging is commonly associated with chronic oxidative stress and mild inflammation that can cause a variety of degenerative diseases. Lactic acid bacteria (LAB) provide several health benefits to the host including antioxidant activity and immune system regulation. However, there is a lack of information regarding the antioxidant mechanisms of probiotics in vivo. Therefore, the aim of this study was to elucidate the possible mechanisms for the preventive effect of LAB on aging. First, 25 LAB strains were screened for finding potential probiotics with high antioxidant capacity using in vitro methods. Second, D-galactose was administered by subcutaneous injection once daily for 8 weeks to establish an aging mouse model to investigate the protective effects and underlying mechanisms of the potential probiotic strain Lactobacillus helveticus KLDS1.8701, identified from the screening. The results in vitro showed that L. helveticus KLDS1.8701 had a better property with remarkable free radical scavenging activity. In vivo, L. helveticus KLDS1.8701 supplementation significantly ameliorated aging-related changes such as decreased organic index, liver injury and increased endotoxin. L. helveticus KLDS1.8701 supplementation reduced hepatic oxidative stress by modulating the Nrf-2 pathway. Notably, L. helveticus KLDS1.8701 supplementation restored the gut microbiota composition to that of the control group, resulting in increased butyrate production and decreased endotoxin production. These findings indicated that L. helveticus KLDS1.8701 supplementation manipulated gut microbiota and its metabolites could attenuate hepatic oxidative stress via the gut–liver axis.

Diabetes has become the third most serious threat to human health, after cancer and cardiovascular disease. Notably, Lactobacillus brevis is the most common species of LAB that produces γ-aminobutyric acid (GABA). The aim of this study is to clarify the effect of time, strain types, antibiotic concentrations, different levels of pH, and intestinal juices in aerobic or anaerobic conditions and the effect of interactions between these factors on the potential properties of KLDS 1.0727 and KLDS 1.0373, furthermore, antagonistic activity against foodborne pathogens. Moreover, another aim is to study the capability of KLDS 1.0727 and KLDS 1.0373 strains as gad gene carriers to express GABA that reduce the risk of type 1 diabetes in C57BL/6 mice as diabetic models. The obtained results exhibited the surprising tolerance of Lactobacillus brevis strains in vitro digestion models mimicking the conditions of the gastrointestinal tract, further, large antagonistic activity against foodborne pathogeneses. In vivo results displayed the significant effect on glucose level reduction, blood plasma, and histological assays of mice organs. As recommended, the use of Lactobacillus brevis strains should be widely shared in the market as a natural source of GABA in pharmaceutical and food applications.

Diabetes has become the second most severe disease to human health. Probiotics are important for maintaining gastrointestinal homeostasis and energy balance and have been demonstrated to play a positive role in the prevention and treatment of metabolic syndromes, such as obesity, inflammation, dyslipidemia, and hyperglycemia. The objective of this study was to screen potential antidiabetic strains in vitro and evaluate its effects in vivo. For the in vitro section, dipeptidyl peptidase IV (DPP-IV) inhibitory and antioxidant activities of 14 candidate Lactobacillus spp. strains were tested. Then hydrophobicity and acid and bile salt tolerance assays were determined. The most promising in vitro strain was further evaluated for its antidiabetic properties in vivo using type 2 diabetes mice induced by high-fat diet and intraperitoneal injection of streptozotocin (STZ). The reference strain for this study was Lactobacillus rhamnosus GG. Results showed that cell-free excretory supernatants and cell-free extracts of Lactobacillus acidophilus KLDS1.0901 had better DPP-IV inhibitory activity, antioxidative activities, and biological characteristics than other strains. At the end of the treatment, we found that L. acidophilus KLDS1.0901 administration decreased the levels of fasting blood glucose (FBG), glycosylated hemoglobin, insulin in serum and AUC_glucose, and increased the level of glucagon-like peptide 1 in serum compared with diabetic mice (p < 0.05). Moreover, L. acidophilus KLDS1.0901 supplementation increased the activities of superoxide dismutase, glutathione peroxidase, the level of glutathione, and reduced the level of malondialdehyde in serum. These results indicated that L. acidophilus KLDS1.0901 could be used as a potential antidiabetic strain; its application as food supplement and drug ingredient is thus recommended.

Enterococcus durans KLDS6.0930 has previously been shown to have probiotic potential. However, being a potential clinical pathogen, it becomes necessary to evaluate its safety status for novel potential probiotic use. The purpose of this study is to systematically evaluate the safety of E. durans KLDS6.0930 based on its genomics, phenotypic characteristics and oral toxicity. The complete genome of E. durans KLDS6.0930 was sequenced and analyzed for safety-related genes. Antibiotic susceptibility and the production of harmful metabolites were tested. A 28-day repeated oral dose toxicity test was implemented in rats. In vitro, E. durans KLDS6.0930 was resistant to five antibiotics, with intrinsic resistances to four antibiotics and no identified genes for the last. E. durans KLDS6.0930 was not hemolytic and virulence factors were non-functional in its genome. E. durans KLDS6.0930 produced a small amount of tyramine and phenethylamine; genes encoding tyramine decarboxylase were identified. In addition, genotype and phenotype analyses showed that the strain did not have the ability to generate D-lactic acid, indole, or nitroreductase. In vivo, E. durans KLDS6.0930 did not induce adverse effects on the organs, hematological and serum biochemical parameters, or cecal bacterial populations in the oral toxicity test. These results indicate that E. durans KLDS6.0930 can be safely used as a potential probiotic for human consumption and animal feed.

Lactobacillus helveticus, an obligatory hetero-fermentative LAB, is Generally Recognized as Safe (GRAS) and is gaining popularity for application in dairy products. Lactic acid bacteria (LAB) play a remarkable role in inhibiting the growth of pathogenic bacteria in food products, without disturbing the sensory attributes of the food. In this study, the screening of the antimicrobial potential of Lactobacillus helveticus KLDS 1.8701 against four food-borne pathogens including Listeria monocytogenes ATCC 19115, Salmonella typhimurium ATCC 14028, Staphylococcus aureus ATCC 25923, and Escherichia coli O157:H7 ATCC 43889 in vitro was inspected using the Oxford cup method and mixed culture inhibition assays. The organic acid production and antimicrobial potential of the cell-free supernatants (CFS) have been evaluated via different treatments and analysis using high performance liquid chromatography (HPLC). The analysis results revealed that KLDS 1.8701 exhibited the highest antimicrobial potential compared to other antimicrobial strains. The antimicrobial activity of KLDS 1.8701 resulted from the organic acids in the culture and CFS. From the study, it was found that carbon sources, as well as organic acid production, accelerate the antimicrobial activity of KLDS 1.8701 and the fructooligosaccharides (FOS) were considered the best for improving the proliferation of KLDS 1.8701 and supporting its antimicrobial action. Results of the mixed culture inhibition assays showed that part of the antimicrobial activity resulted from the inhibitory action of the bacteria itself in culture, and this action required cellular contact between the food-borne pathogens and KLDS 1.8701. Conversely, the results of the antimicrobial spectrum assay revealed that some Lactobacilli remained unaffected by KLDS 1.8701. KLDS 1.8701 might also be favorable for use as a supplementary starter in fermented dairy productions. Furthermore, KLDS 1.8701 could survive well under GI tract conditions. Further studies on in vivo inhibition assays and the probiotic effects are recommended.