Changes of physicochemical and functional properties of processed cheese made with natural cheddar and mozzarella cheeses during refrigerated storage.

The present study aimed to investigate changes of physicochemical and functional properties of the processed cheeses (PCs) made with Cheddar (PC1), Mozzarella (PC2) and both of them at a ratio of 1:1 (PC3) during storage at 4 °C for 4 months. The results showed that the type of natural cheese used affected the composition of PCs with lower fat content in PC2 due to the lower fat content of Mozzarella cheese used. PC2 with lower fat content showed decreased meltability and oil leakage compared with PC1 and PC3. The stretchability of all the samples significantly (P < 0.05) decreased during storage, and PC1 showed lower stretchability. This was confirmed by increased protein hydrolysis of all the samples during the storage with a higher level of proteolysis in PC1, leading to decreased stretchability of PCs. Further low-field nuclear magnetic resonance analysis indicated more entrapped water in cheese due to moisture migration into the cheese matrix that might squeeze the fat globules to aggregate, causing more fat leakage during later stages of storage. This was evidenced by microstructural analysis showing different extents of increase in fat particle sizes and decrease in free serum in all the PC samples over the storage time. Therefore, the present study provides further understanding of the mechanism of quality change of PC during refrigerated storage as affected by proteolytic properties and composition of natural cheese used.

Purification and characterization of a novel low-molecular-weight antimicrobial peptide produced by Lactiplantibacillus plantarum NMGL2.

The present study aimed to purify and characterize a novel low-molecular-weight antimicrobial peptide (AMP) named as PNMGL2 produced by Lactiplantibacillus plantarum NMGL2. The AMP was effectively separated and purified by ethyl acetate extraction and DEAE-Sepharose anion exchange chromatography. Tricine-SDS-PAGE of the purified AMP showed a major protein band below 1.7 kDa, which was identified by MALDI-TOF MS to be a hexapeptide LNFLKK (761.95 Da), and structurally characterized to be combination of helixes and random coil by a PEP-FOLD 3 De novo approach. The antimicrobial activity of LNFLKK was confirmed by chemical synthesis of the peptide that showed clear inhibition (MIC 7.8 mg/mL) against both Gram-positive bacteria (Staphylococcus aureus and Listeria monocytogenes), and Gram-negative bacteria (Enterobacter sakazakii, Escherichia coli and Shigella flexneri). PNMGL2 was pH resistant (pH 2-9), heat stable (121 °C, 30 min), and protease sensitive. Treatment of UV rays, sodium chloride and organic solvents did not decrease the activity. Sequencing of the whole genome of L. plantarum NMGL2 revealed presence of a bacteriocin gene cluster with two putative bacteriocin genes (ORF4 and ORF5) that were not expressed, confirming the significance of PNMGL2 contributing the antimicrobial activity of the strain. This study demonstrated the low-molecular-weight AMP that was uncharacterized in the relevant available databases, suggesting its potential application as a novel natural food preservative.

Effects of the Exopolysaccharide from Lactiplantibacillus plantarum HMX2 on the Growth Performance, Immune Response, and Intestinal Microbiota of Juvenile Turbot, Scophthalmus maximus.

In this study, the exopolysaccharide (EPS) from Lactiplantibacillus plantarum (HMX2) was isolated from Chinese Northeast Sauerkraut. Its effects on juvenile turbot were investigated by adding different concentrations of HMX2-EPS (C: 0 mg/kg, H1: 100 mg/kg, H2: 500 mg/kg) to the feed. Compared with the control group, HMX2-EPS significantly improved the growth performance of juvenile turbot. The activities of antioxidant enzymes, digestive enzymes, and immune-related enzymes were significantly increased. HMX2-EPS could also increase the secretion of inflammatory factors and enhance the immune response of turbot by regulating the IFN signal transduction pathway and exhibit stronger survival rates after the A. hydrophila challenge. Moreover, HMX2-EPS could improve the diversity of intestinal microbiota in juvenile fish, increase the abundance of potential probiotics, and reduce the abundance of pathogenic bacteria. The function of gut microbes in metabolism and the immune system could also be improved. All results showed better effects with high concentrations of HMX2-EPS. These results indicated that HMX2-EPS supplementation in the diet could promote growth, improve antioxidant activity, digestive capacity, and immunity capacity, and actively regulate the intestinal microbiota of juvenile turbot. In conclusion, this study might provide basic technical and scientific support for the application of L. plantarum in aquatic feed.

Amelioration effect of Lactobacillus plantarum KFY02 on low-fiber diet-induced constipation in mice by regulating gut microbiota.

This study aimed to examine the ameliorating effect of Lactobacillus plantarum (LP) KFY02 on low-fiber diet-induced constipation in mice. LP-KFY02 was isolated from the natural fermented yogurt in Korla of Xinjiang. The mice with low-fiber diet-induced constipation in experimental groups were administered 1 × 109 CFU/kg LP-KFY02 (KFY02H) and 1 × 108 CFU/kg LP-KFY02 (KFY02L). After LP-KFY02 treatment with constipation mice, the mice fecal water content, intestinal transit ability and defecation time of constipated mice were improved. The mice fecal flora diversity, abundance and structure of the intestinal flora were regulated to the balanced state. The mice serum levels of gut motility related neuroendocrine factors have been increased, the intestinal mucosal barrier function and gut motility related gene expression were regulated in mice colon tissues. At the same time, the mice colon tissue damage were improved. These parameters in the KFY02H group were close to the normal group. These results suggested that LP-KFY02 could be considered as a potential probiotic to help alleviate low-fiber diet-induced constipation. They also provided a theoretical basis for the study of probiotics to relieve constipation by regulating intestinal flora.

Lactobacillus fermentum CQPC08 protects rats from lead-induced oxidative damage by regulating the Keap1/Nrf2/ARE pathway.

In this experiment, Lactobacillus fermentum CQPC08 (LF-CQPC08) isolated from traditionally fermented pickles was used to study its mitigation effect on lead acetate-induced oxidative stress and lead ion adsorption capacity in rats. In vitro experiments showed that the survival rate in artificial gastric juice and the growth efficiency in artificial bile salt of LF-CQPC08 was 93.6% ± 2.2% and 77.2% ± 0.8%, and the surface hydrophobicity rate was 45.5% ± 0.3%. The scavenging rates of hydroxyl radical, superoxide anion, and 1,1-diphenyl-2-picrylhydrazyl (DPPH) were 47.8% ± 0.9%, 63.9% ± 1.2%, and 83.6% ± 1.5%, respectively, and the reduction power was 107.3 ± 2.8 µmol L-1. LF-CQPC08 could not only adsorb 76.9% ± 1.0% lead ions in aqueous solution but also reduce the lead content in serum, liver, kidneys, and brain tissue of Sprague-Dawley (SD) rats, as well as maintain the cell structure and tissue state of the liver and kidneys. In addition, by examining the indicators of inflammation and oxidation in the serum, liver, and kidneys of SD rats, we found that LF-CQPC08 can reduce the proinflammatory factors interleukin (IL)-1 beta (1ß), IL-6, tumor necrosis factor alpha, and interferon gamma in the body, increase the level of anti-inflammatory factor IL-10, enhance the activity of antioxidant enzymes such as superoxide dismutase and catalase and glutathione levels in serum and organ tissues, and reduce the production of reactive oxygen species and accumulation of lipid peroxide malondialdehyde. LF-CQPC08 can also activate the Keap1/Nrf2/ARE signaling pathway to promote high-level expression of the downstream antioxidants heme oxygenase 1 (HO-1), NAD(P)H : quinone oxidoreductase 1 (NQO1), and γ-glutamylcysteine synthetase (γ-GCS). As food-grade lactic acid bacteria, LF-CQPC08 has great potential and research value in removing heavy metals from food and alleviating the toxicity of heavy metals in the future.

Improvement Effect of Lotus Leaf Flavonoids on Carbon Tetrachloride-Induced Liver Injury in Mice.

In this study, the effect of lotus leaf flavonoids (LLF) on carbon tetrachloride (CCl4)-induced liver injury in mice was studied. CCl4 was injected intraperitoneally to induce liver injury in Kunming mice. Mice were treated with LLF by gavage, and the mRNA expression levels in serum and liver were detected. Compared with the model group, LLF significantly reduced the liver index and serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), triglyceride (TG), and total cholesterol (TC) levels in mice with CCl4-induced liver injury. Pathological observation showed that LLF effectively reduced morphological incompleteness and hepatocyte necrosis in CCl4-treated liver tissue. The result of quantitative polymerase chain reaction (qPCR) indicated that LLF significantly up-regulated the mRNA expression levels of copper/zinc superoxide dismutase (Cu/Zn-SOD), manganese superoxide dismutase (Mn-SOD), and catalase (CAT) and down- regulated the expression levels of tumor necrosis factor-alpha (TNF-α), nuclear factor kappa B (NF-κB), and interleukin-1ß (IL-1ß) (p < 0.05). Thus, LLF is an active ingredient that ameliorates liver injury, and it has good application prospect.