Influence of reuterin-producing Lactobacillus reuteri coupled with glycerol on biochemical, physical and sensory properties of semi-hard ewe milk cheese

Effects of the synbiotic composed of mangiferin and Lactobacillus reuteri 1-12 on type 2 diabetes mellitus rats

Many synbiotics are effective for the prevention and treatment of type 2 diabetes mellitus (T2DM). In the treatment of T2DM, synbiotics often regulate the composition of intestinal flora, which autoinducer-2 (AI-2) may play an important role. Whether the changes of intestinal flora are related to AI-2 during synbiotics treatment of T2DM is a topic worth studying. We elucidated the effects of synbiotic composed of mangiferin and Lactobacillus reuteri 1-12 (SML) on T2DM rats. Male Spraque-Dawley rats were injected intraperitoneally with streptozotocin (STZ) and randomly grouped. After that, biochemical parameters, intestinal flora, fecal AI-2, and intestinal colonization of L. reuteri were detected. The results showed that SML had a hypoglycemic effect and mitigated the organ lesions of the liver and pancreas. Also, SML regulated biochemical parameters such as short chain fatty acids (SCFAs), lipopolysaccharides (LPS), intercellular cell adhesion molecule-1 (ICAM-1), and tumor necrosis factor-α (TNF-α). On the other hand, the proportion of probiotics, such as Lactobacillus acidophilus, L. reuteri, Bifidobacterium pseudolongum, Lactobacillus murinus, and Lactobacillus johnsonii, were elevated by the treatment of SML. In addition, SML promoted the colonization and proliferation of L. reuteri in the gut. Another thing to consider was that AI-2 was positively correlated with the total number of OTUs sequences and SML boosted AI-2 in the gut. Taken together, these results supported that SML may modulate intestinal flora through AI-2 to treat T2DM. This study provided a novel alternative strategy for the treatment of T2DM in future.

Application of the Reuterin System as Food Preservative or Health-Promoting Agent: A Critical Review

The reuterin system is a complex multi-component antimicrobial system produced by Limosilactobacillus reuteri by metabolizing glycerol. The system mainly includes 3-hydroxypropionaldehyde (3-HPA, reuterin), 3-HPA dimer, 3-HPA hydrate, acrolein and 3-hydroxypropionic acid, and has great potential to be applied in the food and medical industries due to its functional versatility. It has been reported that the reuterin system possesses regulation of intestinal flora and anti-infection, anti-inflammatory and anti-cancer activities. Typically, the reuterin system exerts strong broad-spectrum antimicrobial properties. However, the antimicrobial mechanism of the reuterin system remains unclear, and its toxicity is still controversial. This paper presents an updated review on the biosynthesis, composition, biological production, antimicrobial mechanisms, stability, toxicity and potential applications of the reuterin system. Challenges and opportunities of the use of the reuterin system as a food preservative or health-promoting agent are also discussed. The present work will allow researchers to accelerate their studies toward solving critical challenges obstructing industrial applications of the reuterin system.

Efficacy of Reuterin and Bacteriocins Nisin and Pediocin in the Preservation of Raw Milk from Dairy Farms

Research background

In the current scenario of milk production in developing and developed countries, several factors influence the shelf-life of raw milk and add significant numbers of microbial contaminants that drastically lower the initial microbial quality leading to milk spoilage by the time it reaches the processing units.

Experimental approach

The present study was undertaken to investigate the biopreservative efficacy of reuterin system along with different combinations of bacteriocins in controlling the initial microflora of raw milk at farm level. Lactobacillus reuteri strain LR47, having effective antimicrobial activity, was shortlisted from our previous study and further characterized for reuterin production and tested in raw milk system.

Results and conclusions

Preliminary testing of the cell-free supernatant from L. reuteri LR47 demonstrated significant growth inhibition of the majority of the tested bacterial indicators of milk spoilage. Further genetic analysis of the L. reuteri LR47 revealed the presence of two genes (pduC and dhaB) involved in the utilization of glycerol to produce reuterin via two different pathways. The strain LR47 was also found to possess comparatively higher capacity to convert glycerol into reuterin when checked through colorimetric assay. In the raw milk biopreservation experiment with reuterin alone or in combination with bacteriocins, the highest level of growth suppression in the total bacterial load and coliform counts was observed in the sample that was treated with a combination of reuterin, nisin and pediocin. The treatment combining these three natural biopreservatives at specific concentrations was able to maintain the initial microbial quality and extend the shelf-life of raw milk by 6 h at 37 °C based on the microbial counts and physicochemical properties, viz. pH and titratable acidity. In conclusion, the results confirm that the use of reuterin in combination with bacteriocins is a promising approach for temporary control of the raw milk microflora and extension of its shelf-life until further processing.

Novelty and scientific contribution

This study demonstrates for the first time the use of reuterin for the extension of shelf-life of raw milk as an alternative treatment method.

Antagonistic effects of Lactobacillus reuteri against Escherichia coli O157:H7 in white-brined cheese under different storage conditions

This study aimed to investigate the survival of the foodborne pathogen Escherichia coli O157:H7 in white-brined cheeses as influenced by the presence of Lactobacillus reuteri. The white cheeses were made from pasteurized bovine milk inoculated with E. coli O157:H7 (cocktail of 3 strains) to achieve ∼5 log₁₀ cfu/g with absence or presence of Lb. reuteri (∼6 log₁₀ cfu/g). Cheese samples were brined in 10% or 15% NaCl solution and stored at 10°C and 25°C for 28 d. The white-brined cheeses were assessed for salt content, pH, water activity (A_w), and numbers of E. coli O157:H7, Lb. reuteri, nonstarter lactic acid bacteria (NSLAB), yeasts, and molds. Results showed that E. coli O157:H7 survived in cheese stored in both brine solutions at 10°C and 25°C regardless of the presence of Lb. reuteri. A substantial reduction was observed in cheese stored in 10% NaCl brine at 25°C, followed by cheese stored in 15% NaCl brine at 10°C by 2.64 and 2.16 log₁₀ cfu/g, respectively, in the presence of Lb. reuteri and by 1.02 and 1.87 log₁₀ cfu/g, respectively, in the absence of Lb. reuteri under the same conditions. The pathogen in brine solutions survived but at a lower rate. Furthermore, the growth of Lb. reuteri and NSLAB were enhanced or slightly decreased in cheese and brine by 28 d, respectively. The salt concentrations of cheese ranged from 4 to 6% and 5 to 7% (wt/wt), during 28-d ripening in 10 and 15% brine, respectively. Values of pH and A_w slightly increased at d 1 after exposure to brine and reached 4.69 to 6.08 and 0.91 to 0.95, respectively, in all treatments. Therefore, the addition of Lb. reuteri can be used as a biopreservation method to inhibit the survival of E. coli O157:H7 in white-brined cheese when combined with the appropriate temperature, NaCl level, and storage time.

Isolation and characterization of five novel probiotic strains from Korean infant and children faeces

Probiotics are dietary supplements containing viable, non-pathogenic microorganisms that interact with the gastrointestinal microflora and directly with the immune system. The possible health effects of probiotics include modulating the immune system and exerting antibacterial, anticancer, and anti-mutagenic effects. The purpose of this study was to isolate, identify, and characterize novel strains of probiotics from the faeces of Korean infants. Various assays were conducted to determine the physiological features of candidate probiotic isolates, including Gram staining, 16S rRNA gene sequencing, tolerance assays to stimulated gastric juice and bile salts, adherence ability assays, antibiotic susceptibility testing, and assays of immunomodulatory effects. Based on these morphological and biochemical characteristics, five potential probiotic isolates (Enterococcus faecalis BioE EF71, Lactobacillus fermentum BioE LF11, Lactobacillus plantarum BioE LPL59, Lactobacillus paracasei BioE LP08, and Streptococcus thermophilus BioE ST107) were selected. E. faecalis BioE EF71 and L. plantarum BioE LPL59 showed high tolerance to stimulated gastric juice and bile salts, and S. thermophilus BioE ST107 as well as these two strains exhibited stronger adherence ability than reference strain Lactobacillus rhamnosus GG. All five strains inhibited secretion of lipopolysaccharide-induced pro-inflammatory cytokines IL-6 and TNF-α in RAW264.7 macrophages in vitro. L. fermentum BioE LF11, L. plantarum BioE LPL59, and S. thermophilus BioE ST107 enhanced the production of anti-inflammatory cytokine IL-10. Overall, our findings demonstrate that the five novel strains have potential as safe probiotics and encouraged varying degrees of immunomodulatory effects.

Evaluation of Fresh Cheese Quality Prepared with Newly Isolated Nisin Z-Producing Lactococcus lactis Bacteria

The main task of the present study was to evaluate an impact of three nisin Z-producing Lactococcus lactis bacteria newly isolated from raw goat milk for some fresh cow cheese characteristics during the storage. Microbiological evaluation for Listeria monocytogenes, Staphylococcus aureus, and viable lactic acid bacteria counts and determination of pH, titratable acidity, and lactic acid concentration of produced cheese were performed after 0, 24, 48, 72, and 96 h. Sensory analysis for the evaluation of acidity, flavor intensity, color intensity, bitterness, and crumbliness of prepared cheese was performed. The changes of volatile compounds in fresh cheese were evaluated using headspace solid phase microextraction (SPME) coupled with gas chromatography-mass spectrometry. Chemometric methods were applied for the data analysis. Study showed that tested bacteria are suitable for the manufacturing of fresh cheese and possible application for fresh cheese biopreservation, as pathogenic bacteria did not grow during 4 days (96 h); chemometric analysis revealed that L. lactis strain LL56 was the most similar to commercially available L. lactis ATCC11454.