The effect of ion environment changes on retention protein behavior during whey ultrafiltration process.

The factors affecting membrane fouling are very complex. In this study, the membrane fouling process was revealed from the perspective of ion environment changes, which affected the whey protein structure during ultrafiltration. It was found that the concentrations of Ca2+ and Na+ were overall increased and the concentrations of K+, Mg2+ and Zn2+ were decreased at an ultrafiltration time of 11 min, which made more hydrophilic groups buried inside and increased the content of α-helix, leading to more protein aggregation. The relatively higher K+ ratio in retention could lead to an antiparallel ß-sheet configuration, aspartic acid, glutamic acid and tryptophan increased, which resulted in more protein aggregation and deposition on the membrane surface at 17 min. When the ion concentration and ratio restored the balance and were close to the initial state in retention, the protein surface tension decreased, and the hydrophilic ability increased at 21-24 min.

Lactobacillus buchneri S-layer protein-coated liposomes loaded with ß-cyclodextrin-carvacrol inclusion complexes for the enhancement of antibacterial effect.

This article describes the development of a novel liposome nanocarrier system. Carvacrol (Car) is first embedded in ß-cyclodextrin (ß-CD) by the freeze-drying method to form the ß-cyclodextrin-carvacrol inclusion compound (ß-CD-Car), and then ß-CD-Car liposomes (ß-CD-Car-LPs) and ß-CD-Car liposomes coated with S-layer proteins (SLPs) from Lactobacillus buchneri 20023 (SLP/ß-CD-Car-LPs) were prepared. The liposomes were characterized, and their stabilities, in vitro release characteristics, and antibacterial activities were investigated. Results showed that the fabricated liposome SLP/ß-CD-Car-LPs was nanosized, oval and homogenous, with the particle size of 229.1 ± 6.81 nm, the polydispersity index of 0.139, and the zeta potential of 27.9 mV. Measurements based on Triton X-100 resistance indicated that the SLP-coated liposomes were more stable than naked liposomes. The in vitro release study results showed that the rate of release from SLP-coated liposomes was much lower than that from uncoated liposomes. The minimum inhibitory activity (MIC) of SLP/ß-CD-Car-LPs (0.05 mg/mL) was 6.4 times higher than that of the free carvacrol (0.32 mg/mL) and was twice that of ß-CD-Car-LPs (0.1 mg/mL). In general, the stability, antibacterial activity, and sustained release effect of ß-CD-Car-LPs modified with SLPs were improved. Findings suggested that SLP-coated liposomes could be developed as a favorable delivery system for potential applications in the food industry.

Ilexgenin A induces B16-F10 melanoma cell G1/S arrest in vitro and reduces tumor growth in vivo.

The present study aimed to investigate the anti-tumor activity of Ilexgenin A in B16-F10 murine melanoma and to evaluate its effect on the production of tumor-associated inflammatory cytokines. In vitro, our study showed that Ilexgenin A inhibited the proliferation of B16-F10 murine melanoma cells in a dose- and time-dependent manner, and this effect could be ascribed to the arrest of the cell cycle at G0/G1. In vivo, we evaluated the anti-tumor activity of Ilexgenin A in a tumor-bearing mouse model. The results showed that Ilexgenin A reduced the tumor weight by 51.13% (p<0.01). The Ilexgenin A treatment groups showed no apparent side effects during the treatment period. In addition, a histological analysis revealed that Ilexgenin A changed the cell morphology, and induced large areas of necrosis that correlated with a reduction in tumor size. The detection of inflammatory cytokines indicated that the IL-6 level decreased (p<0.001) and the TNF-α level increased (p<0.01) in mice treated with Ilexgenin A. Ilexgenin A also inhibited the IL-6 production of macrophages stimulated by melanoma conditioned medium (MCM) significantly (p<0.001). Importantly, Ilexgenin A dramatically prolonged survival time (p<0.001). In conclusion, Ilexgenin A could be regarded as a promising agent for the treatment of melanoma; it exerts anti-melanoma activity by arresting the cell cycle at G0/G1 and regulating IL-6 and TNF-α production.

Alleviating effects of Lactobacillus strains on pathogenic Vibrio parahaemolyticus-induced intestinal fluid accumulation in the mouse model.

The aim of this study was to evaluate the probiotic effects of Lactobacillus strains against Vibrio parahaemolyticus causing gastroenteritis. Six-week-old ICR mice were pretreated with four Lactobacillus strains at three dosages, and then challenged with V. parahaemolyticus TGqx01 (serotype O3:K6). The results showed that V. parahaemolyticus TGqx01 caused severe intestinal fluid accumulation (FA) and villi damage in control mice which were pretreated with phosphate-buffered saline. In contrast, significant alleviation of FA was seen in mice pretreated by with a high dose of Lactobacillus strains (P < 0.05, n = 6) but not in mice that received low-dose pretreatments. Among middle-dose treatments, two highly adhesive strains, Lactobacillus rhamnosus H15 and Lactobacillus brevis Y29-4, significantly decreased intestinal FA and villi damage in treated mice (P < 0.05). Two low-adhesive strains, Lactobacillus acidophilus Y14-3 and Lactobacillus fermentum F16-6, had no significant alleviating effects. At the same dosing levels, no significant differences in FA were observed in mice pretreated with strains with similar adhesive abilities but different antagonistic activities. Our findings suggest that Lactobacillus strains can alleviate V. parahaemolyticus-induced intestinal FA in mice, and the doses required for in vivo efficacy depend more on adhesive ability than on the antibacterial activity of strains.

Predictive model of Vibrio parahaemolyticus growth and survival on salmon meat as a function of temperature.

The growth and survival curves of a strain of pandemic Vibrio parahaemolyticus TGqx01 (serotype O3:K6) on salmon meat at different storage temperatures (range from 0 degrees C to 35 degrees C) were determined. In order to model the growth or inactivation kinetics of this pathogen during storage, the modified Gompertz and Weibull equations were chosen to regress growth and survival curves, respectively, and both equations produced good fit to the observed data (the average R2 value equals to 0.990 for modified Gompertz and 0.920 for Weibull equation). The effect of storage temperature on the specific growth rate (mu) was modeled by square root type equation, and the relationship between mu and lag time (lambda) was described by a rule of mu x lambda = constant. The shape factor (n) and scale factor (b) values of the Weibull equations versus the temperature (degrees C) were plotted and the temperature effects on these parameters were described by two linear empirical equations. The predicted growth and survival curves from the model were compared to real enumeration results, using the correlation coefficient (R2), bias factor (Bf) and accuracy factor (Af), to assess the performance of the established model. The results showed that the overall predictions for V. parahaemolyticus TGqx01 growth or inactivation on salmon at tested temperatures agreed well with observed plate counts, and the average R2, Bf and Af values were 0.958, 1.019 and 1.035, respectively.

Probiotic properties of lactic acid bacteria isolated from stool samples of longevous people in regions of Hotan, Xinjiang and Bama, Guangxi, China.

A total of 567 lactic acid bacteria (LAB) strains were isolated from the stool samples of longevous people in regions of Hotan, Xinjiang and Bama, Guangxi, China. In order to reduce the number of strains for further examinations, 36 isolates were screened out for further examination whilst the other strains, which had lower probiotic properties, were not suitable for yogurt production due to the absence of growth in pH 3.5 MRS medium and no curding during fermentation, and so were excluded. The result of identification by API, sequence analysis of 16S rRNA and random amplified polymorphic DNA (RAPD) analysis showed that there were three strains of Lactobacillus acidophilus, 10 strains of Lactobacillus rhamnosus, three strains of Lactobacillus casein, three strains of Lactobacillus brevis, two strains of Enterococcus faecium, two strains of Enterococcus faecalis, four strains of Bifdibacterium infantis, three strains of Bifdibacterium brevise, three strains of Bifdibacterium bifidium, two strains of Bifdibacterium adolecentis and one strain of Bifdibacterium longam among the 36 isolates. These strains were evaluated by in vitro methods including survival upon exposure to pH 2.0, 3.0 and/or 0.3% oxgall and adhesion to the human colon adenocarcinoma cell line Caco-2 as well as antimicrobial activity against potential pathogens. The results presented here show that L. rhamnosus LV108, L. rhamnosus F, B. brevise R39 and B. infantis R42 are acid and bile tolerant, adhere to the cultured human intestinal Caco-2 cell line, antagonistic activity against potential pathogenic bacteria infection in vitro, and so are potential strains for probiotic use.

Isolation and molecular characterization of Vibrio parahaemolyticus from fresh, low-temperature preserved, dried, and salted seafood products in two coastal areas of eastern China.

A total of 1293 seafood samples from fishing farm, retail markets, restaurants and cooking rooms of hotels in Jiangsu province and Shanghai city of China were collected and analyzed for the prevalence of Vibrio parahaemolyticus during July to October in 2007. Two hundred and fifty one isolates of V. parahaemolyticus were identified, of which 8 isolates were positive for tdh and 2 were positive for trh gene. Three tdh positive isolates were identified from low-temperature preserved seafood samples and 5 isolates from fresh seafood samples, of these tdh positive isolates, 3 were positive in ORF8-PCR test. The genetic diversity among V. parahaemolyticus isolates was assessed using random amplified polymorphic DNA (RAPD)-PCR and the results showed that there were 33 different genetic patterns that were clustered into nine groups (groups A to I) at 82% similarity level. About 31.9% of the isolates belong to type III9d that were widely distributed in fresh, iced, frozen, dried and salted seafood samples. Seven tdh positive isolates belonged to group A and one belonged to group C, 2 trh positive isolates were type I10d belonging to group F, which was identical to that of reference strains isolated from patients. This study demonstrated genetic variability within V. parahaemolyticus isolates from seafood in Chinese markets and confirmed the presence of toxigenic V. parahaemolyticus not only in fresh but also in iced and frozen seafood products indicating that low-temperature preserved seafood might be also a vehicle for transmitting pathogenic V. parahaemolyticus.