Simulated Gastrointestinal Environment Research Articles

Changes of Antibiotic Resistance Phenotype in Outbreak-Linked Salmonella enterica Strains after Exposure to Human Simulated Gastrointestinal Conditions in Chicken Meat

Fifteen outbreak-linked Salmonella enterica strains in chicken meat were evaluated under simulated human gastrointestinal conditions for their resistance and susceptibility to 11 antibiotics from seven antibiotic classes. The MIC of each antibiotic was determined by microdilution in broth before and after the exposure of each strain to a continuous system simulating the conditions in the human mouth, esophagus-stomach, duodenum, and ileum. Strains were inoculated onto chicken breast (9 g; inoculated at 5 log CFU/g) prior to exposure. Data were interpreted according Clinical and Laboratory Standards Institute breakpoints. After the in vitro digestion, 12 Salmonella strains with reduced susceptibility to ciprofloxacin (CIP) changed to CIP resistant. The ceftriaxone (CTX)-intermediate Salmonella Newport strain changed to CTX resistant. The ampicillin (AMP)-susceptible Salmonella Heidelberg strain changed to AMP resistant, and the sulfamethoxazole-trimethoprim (SXT)-susceptible strains of Salmonella serovars Typhimurium, Agona, Newport, Albany, and Corvallis changed to SXT resistant. The Salmonella Heidelberg, Salmonella Newport, Salmonella Albany, and Salmonella Corvallis strains had the highest frequency of changes in antibiotic susceptibility with new resistant phenotypes to AMP and CIP, CTX and SXT, CIP and SXT, and CIP and SXT, respectively. Conditions imposed by a simulated gastrointestinal environment changed the susceptibility of S. enterica strains to clinically relevant antibiotics and should be considered in the selection of therapies for human salmonellosis.

Pluronic F127/Pluronic P123/vitamin E TPGS mixed micelles for oral delivery of mangiferin and quercetin: Mixture-design optimization, micellization, and solubilization behavior

Mixed micelles (MMs) of Pluronic F127 (F127), Pluronic P123 (P123), and Vitamin E TPGS (TPGS) copolymers were prepared by the thin-film sonication method to encapsulate two phenolics with different polarities: magniferin (MGF) and quercetin (QCT). Mixture design was applied for the multi-response optimization of formulations of MGF-loaded MMs (MGF-MMs) and QCT-loaded MMs (QCT-MMs) with high encapsulation efficiency (EE) and drug loading (DL), but low critical micelle concentration (CMC). The optimal mass fractions of F127/P123/TPGS were 0.120/0.328/0.552 for MFG-MMs and 0.131/0.869/0.000 for QCT-MMs, providing EE (>95% (w/w)) and DL (>4.5% (w/w)) higher than those obtained by their individual copolymer components. The CMCs of MFG/QCT-MMs, detected by dynamic light scattering (DLS), were 0.009 ± 0.001 and 0.011 ± 0.001% (w/v), respectively, slightly lower than those obtained by profile analysis tensiometry (PAT). The results revealed that the PAT-CMC represented complete MM formation, while the DLS-CMC detected mono-molecular micelles. The MGF/QCT-MMs showed spherical morphology with diameters of 14.26 ± 0.52 and 21.50 ± 0.37 nm, and their zeta-potentials were −2.89 ± 1.70 and −3.22 ± 1.92 mV, respectively. Nuclear overhauser effect spectroscopy showed that MGF located in both hydrophilic and hydrophobic parts of MMs by orienting its xanthone backbone towards the core, but its glucoside close to the corona. QCT was preferentially located in the PPO core. Both MGF/QCT-MMs had excellent dissolution ability and sustained release in the simulated gastrointestinal environment. This study demonstrated that mixture design was successfully applied for multi-response optimization MM formulations of MGF and QCT, and the developed MMs had potential application as nanoparticle-based drug delivery systems.

Viabilities of Lactobacillus rhamnosus ASCC 290 and Lactobacillus casei ATCC 334 (in free form or encapsulated with calcium alginate-chitosan) in yellow mombin ice cream

This research verified the behavior of Lactobacillus rhamnosus and Lactobacillus casei added to ice cream in free form or encapsulated with alginate-chitosan by comparing their: (1) resistance to low temperature; (2) encapsulation efficiency and (3) cell survivability in a simulated gastrointestinal environment. Calcium alginate-chitosan capsules were produced by extrusion method. The ice cream samples with probiotics were stored at −18 °C for 150 days, and the pH, titratable acidity, the cell viability of the probiotics and the gastrointestinal simulation were analyzed. Free L. casei (−1.64 log) were more resistant to freezing than free L. rhamnosus (−1.92 log). L. rhamnosus and L. casei presented encapsulation efficiencies of 73.8% and 79.5%, respectively. In the gastrointestinal simulation, 86.2% L. rhamnosus (−0,83 log) and 84% L. casei (−1,3 log) were protected by the alginate-chitosan capsules. The results demonstrated that microcapsules reduce cell loss in frozen storage and in simulated gastrointestinal conditions. The reduction in cell viability of encapsulated L. rhamnosus was superior to that of its free form, showing that the encapsulation process is not advantageous for all probiotic species. Therefore, considering cellular losses, the best option for preparing functional yellow mombin ice cream is to use free L. rhamnosus or encapsulated L. casei.

Identification and Molecular Docking Study of a Novel Angiotensin-I Converting Enzyme Inhibitory Peptide Derived from Enzymatic Hydrolysates of Cyclina sinensis.

Marine-derived angiotensin-I converting enzyme (ACE) inhibitory peptides have shown potent ACE inhibitory activity with no side effects. In this study, we reported the discovery of a novel ACE-inhibitory peptide derived from trypsin hydrolysates of Cyclina sinensis (CSH). CSH was separated into four different molecular weight (MW) fractions by ultrafiltration. Fraction CSH-I showed the strongest ACE inhibitory activity. A peptide was purified by fast protein liquid chromatography (FPLC) and reversed-phase high-performance liquid chromatography (RP-HPLC) and its sequence was determined to be Trp-Pro-Met-Gly-Phe (WPMGF, 636.75 Da). The Lineweaver-Burk plot showed that WPMGF was a competitive inhibitor of ACE. WPMGF showed a significant degree of stability at varying temperatures, pH, and simulated gastrointestinal environment conditions. We investigated the interaction between this pentapeptide and ACE by means of a flexible molecular docking tool. The results revealed that effective interaction between WPMGF and ACE occurred mainly through hydrogen bonding, hydrophobic interactions, and coordination bonds between WPMGF and Zn(II). In conclusion, our study indicates that a purified extract derived from Cyclina sinensis or the WPMGF peptide could potentially be incorporated in antihypertensive functional foods or dietary supplements.

Design and synthesis of rosiglitazone-ferulic acid-nitric oxide donor trihybrids for improving glucose tolerance

Glucose intolerance is associated with metabolic syndrome and type 2 diabetes mellitus (T2DM) while some new therapeutic drugs, such as rosiglitazone (Rosi), for T2DM can cause severe cardiovascular side effects. Herein we report the synthesis of Rosi-ferulic acid (FA)-nitric oxide (NO) donor trihybrids to improve glucose tolerance and minimize the side effects. In comparison with Rosi, the most active compound 21 exhibited better effects on improving glucose tolerance, which was associated with its NO production, antioxidant and anti-inflammatory activities. Furthermore, 21 displayed relatively high stability in the simulated gastrointestinal environments and human liver microsomes, and released Rosi in plasma. More importantly, 21, unlike Rosi, had little stimulatory effect on the membrane translocation of aquaporin-2 (AQP2) in kidney collecting duct epithelial cells. These, together with a better safety profile, suggest that the trihybrids, like 21, may be promising candidates for intervention of glucose intolerance-related metabolic syndrome and T2DM.

Chemical Form and Bioaccessibility of Mercury in Traditional Tibetan Medicines

Extremely high mercury (Hg) concentrations have been identified in traditional Tibetan medicine (TTM) products, but the chemical form and bioaccessibility of Hg remain unknown. We conducted experiments to explore whether the Hg contained in TTM is toxic. We determined that HgS is not the exclusive form of Hg in TTM; other compounds could be present in substantial quantities, ranging from 2 to 52% of the total Hg in commonly used TTMs. A substantial amount of Hg could be released from TTM after ingestion. In total, an average of 12 μg of Hg (mostly inorganic)/g (range of 0.41–25 μg of Hg/g) in TTMs was released into the liquid phase in simulated human gastrointestinal environments. However, different from the results from ingestion by fish, the release of Hg from TTM in the intestinal environment is larger than that in the gastric environment by a factor of 2. In the case of joint ingestion with protein-rich products, releases of methyl Hg and inorganic Hg from TTM in gastrointestinal environments could be...

Chitosan/alginate nanoparticles as a promising approach for oral delivery of curcumin diglutaric acid for cancer treatment

Curcumin diglutaric acid (CG) is a prodrug of curcumin that shows better solubility and antinociceptive activity compared to curcumin. To improve its properties further, CG was encapsulated into polysaccharide-based nanoparticles in this study. A chitosan/alginate nanoparticulate system was chosen for encapsulation of CG due to its biocompatibility, biodegradability, non-toxicity, mucoadhisiveness and good film formation. CG-loaded chitosan/alginate nanoparticles were prepared by o/w emulsification and ionotropic gelification, with the conditions optimized using response surface methodology. A chitosan/alginate mass ratio of 0.04:1, CG concentration of 3 mg/mL and Pluronic®F127 concentration of 0.50% (w/v) were determined to be optimal for the nanoparticle preparation. FTIR and XRD confirmed encapsulation of CG into the chitosan/alginate nanoparticles. The CG-loaded chitosan/alginate nanoparticles showed better stability under UV radiation and in a simulated gastrointestinal environment, compared to a CG dispersion in water. The nanoparticles showed slow cumulative release of CG in simulated gastrointestinal fluids without enzymes and in body fluid. A Weibull model of the best fit for all conditions suggested that the release pattern of CG from CG-loaded chitosan/alginate nanoparticles was mainly controlled by Fickian diffusion and erosion of polymer materials. Finally, CG-loaded chitosan/alginate nanoparticles showed higher in vitro cellular uptake in human epithelial colorectal adenocarcinoma (Caco-2 cells) and better anticancer activity against Caco-2, human hepatocellular carcinoma (HepG2) and human breast cancer (MDA-MB-231) cells. Therefore, the CG-loaded chitosan/alginate nanoparticles are a promising approach for oral administration of CG for cancer treatment.

Dissolution Behavior and Biodurability of Ingested Engineered Nanomaterials in the Gastrointestinal Environment.

Engineered nanomaterials (ENM) are extensively used as food additives in numerous food products, and at present, little is known about the fate of ingested ENM (iENM) in the gastrointestinal (GI) environment. Here, we investigated the dissolution behavior, biodurability, and persistence of four major iENM (TiO2, SiO2, ZnO, and two Fe2O3) in individual simulated GI fluids (saliva, gastric, and intestinal) and a physiologically relevant digestion cascade (saliva → gastric → intestinal) in the fasted state over physiologically relevant time frames. TiO2 was found to be the most biodurable and persistent iENM in simulated GI fluids with a maximum of only 0.42% (4 μM Ti4+ ion release) dissolution in cascade digestion, followed by iron oxides, of which the rod-like morphology was more biodurable and persistent (0.7% maximum dissolution, 8.7 μM Fe3+) than the acicular one (2.27% maximum dissolution, 16.7 μM Fe3+) in the cascade digestion, respectively. SiO2 and ZnO were less biodurable than Fe2O3, with 65.5% (416 μM Si4+) and 100% (1718.1 μM Zn2+) dissolution in the gastric phase, respectively. In the intestinal phase, however, Si4+ ions reprecipitated, possibly due to sudden pH changes, while ZnO remained completely dissolved. These observations were also confirmed using high-resolution particle size and concentration, and electron microscopy, time-dependent analysis. In terms of decreasing biodurability and persistence in the simulated GI environment, the tested nanomaterials can be ranked as follows: TiO2 ≫ rod-like Fe2O3 > acicular Fe2O3 ≫ SiO2 > ZnO, which is in agreement with limited animal biokinetics data. Chronic uptake of these iENM as particles or ions by the GI tract, especially in the presence of a food matrix and authentic digestive media, and associated implications for human health warrants further investigation.

Proteomic changes in EHEC O157:H7 under catechin intervention

Catechin exhibits antimicrobial activity against various microorganisms, such as EHEC O157:H7. This study reports the bactericidal effect of catechin on EHEC O157:H7 in simulated human gastrointestinal environment and the underlying antibacterial mechanism. Bacteriostasis test results showed that the minimum bactericidal concentration of catechin for EHEC O157:H7 was 5 g/L. The bactericidal effect of catechin in the gastrointestinal juice became more significant with increased culture time, and catechin exhibited a synergistic effect with bile salt in inhibiting EHEC O157:H7. Changes in the profile of protein expression in EHEC O157:H7 in response to catechin intervention were investigated. Two-dimensional electrophoresis identified 34 proteins with significantly altered expression. A total of 2 and 12 proteins were upregulated and downregulated, respectively. However, 20 proteins disappeared. No new protein was expressed compared with the control. Hence, catechin intervention resulted in diverse changes in the expression of proteins associated with cell structure and genetic information processing. Catechin could cause the disappearance of certain proteins or the destruction of certain peptides. These processes lead to the inhibition of EHEC O157: H7 cells.

Entrapping of Nanoparticles in Yeast Cell Wall Microparticles for Macrophage-Targeted Oral Delivery of Cabazitaxel

In this work, a nano-in-micro carrier was constructed by loading polymer-lipid hybrid nanoparticles (NPs) into porous and hollow yeast cell wall microparticles (YPs) for macrophage-targeted oral delivery of cabazitaxel (CTX). The YPs, primarily composed of natural β-1,3-d-glucan, can be recognized by the apical membrane receptor, dectin-1, which has a high expression on macrophages and intestinal M cells. By combining electrostatic force-driven self-deposition with solvent hydration/lyophilization methods, the positively charged NPs loaded with CTX or fluorescence probes were efficiently packaged into YPs, as verified by scanning electron microscope (SEM), atomic force mircoscope (AFM), and confocal laser scanning microscopy (CLSM) images. NP-loaded YPs (NYPs) showed a slower in vitro drug release and higher drug stability compared with NPs in a simulated gastrointestinal environment. Biodistribution experiments confirmed a widespread distribution and extended retention time of NYPs in the intestinal tract after oral administration. Importantly, a large amount of NYPs were primarily accumulated and transported in the intestinal Peyer's patches as visualized in distribution and absorption site studies, implying that NYPs were mainly absorbed through the lymphatic pathway. In vitro cell evaluation further demonstrated that NYPs were rapidly and efficiently taken up by macrophages via receptor dectin-1-mediated endocytosis using a mouse macrophage RAW 264.7 cell line. As expected, in the study of in vivo pharmacokinetics, the oral bioavailability of CTX was improved to 32.1% when loaded in NYPs, which is approximately 5.7 times higher than that of the CTX solution, indicating the NYPs are efficient for oral targeted delivery. Hence, this nano-in-micro carrier is believed to become a hopeful alternative strategy for increasing the oral absorption of small molecule drugs.

Encapsulation of copigmented anthocyanins within polysaccharide microcapsules built upon removable CaCO3 templates

This work fabricated natural polysaccharide-based polyelectrolyte microcapsules via layer-by-layer assembly (LBL) as carriers for copigmented anthocyanins. For this purpose, the chondroitin sulfate (CHS)/anthocyanin copigmented complexes were coprecipitated into spherical templates created by formation of CaCO3 precipitates. This template complex formation is then followed by deposition of oppositely charged CHS and chitosan (CS), and subsequent dissolution of CaCO3 core. We found that copigmentation with CHS of moderate concentration increased the encapsulation efficiency of anthocyanin in CaCO3, favored anthocyanin retention in the microcapsule and improved the prolonged release of anthocyanin in a simulated gastrointestinal environment. The mechanism behind these observations was hypothesized to be related to the decreased micropolarity and microviscosity in the matrix-type interior of hybrid microcapsules. These results strongly support the combined use of polyelectrolyte microencapsulation and copigmentation techniques for the development of novel systems targeting the stabilization and controlled release of water-soluble molecules such as the anthocyanins studied herein.

Synthesis of stimuli–responsive chitosan–based hydrogels by Diels–Alder cross–linking `click´ reaction as potential carriers for drug administration

Stimuli–responsive chitosan–based hydrogels for biomedical applications using the Diels–Alder reaction were prepared. Furan modified chitosan (Cs–Fu) was cross–linked with polyetheramine derived bismaleimide at different equivalent ratios in order to determine the effect in the swelling and release properties on the final CsFu:BMI hydrogels. The Diels Alder cross–linking reaction was monitored by UV–vis spectroscopy and rheological measurements. Both the sol–gel transition value and the final storage modulus for the different formulations were similar and close to 40 min and 400 Pa, respectively. On the contrary, the swelling degree was found to be strongly dependent on the amount of bismaleimide, mainly in acidic medium, where the increased cross–linking reduced the swelling value in 25%, but maintaining the sustained drug release in the simulated gastrointestinal environment. Our study suggested that these DA–cross–linked chitosan hydrogels could be potential carriers for targeted drug administration.

Differential impact of the cheese matrix on the postprandial lipid response: a randomized, crossover, controlled trial

Background: In a simulated gastrointestinal environment, the cheese matrix modulates dairy fat digestion. However, to our knowledge, the impact of the cheese matrix on postprandial lipemia in humans has not yet been evaluated.Objective: In healthy subjects, we compared the impact of dairy fat provided from firm cheese, soft cream cheese, and butter on the postprandial response at 4 h and on the incremental area under the curve (iAUC) of plasma triglycerides.Design: Forty-three healthy subjects were recruited to this randomized, crossover, controlled trial. In random order at intervals of 14 d and after a 12-h fast, subjects ingested 33 g fat from a firm cheese (young cheddar), a soft cream cheese (cream cheese), or butter (control) incorporated into standardized meals that were matched for macronutrient content. Plasma concentrations of triglycerides were measured immediately before the meal and 2, 4, 6, and 8 h after the meal.Results: Cheddar cheese, cream cheese, and butter induced similar increases in triglyceride concentrations at 4 h (change from baseline: +59%, +59%, and +62%, respectively; P = 0.9). No difference in the triglyceride iAUC0-8 h (P-meal = 0.9) was observed between the 3 meals. However, at 2 h, the triglyceride response caused by the cream cheese (change from baseline: +44%) was significantly greater than that induced by butter (change from baseline: +24%; P = 0.002) and cheddar cheese (change from baseline: +16%; P = 0.0004). At 6 h, the triglyceride response induced by cream cheese was significantly attenuated compared with that induced by cheddar cheese (change from baseline: +14% compared with +42%; P = 0.0004).Conclusion: This study demonstrates that the cheese matrix modulates the impact of dairy fat on postprandial lipemia in healthy subjects. This trial was registered at clinicaltrials.gov as NCT02623790.

Amorphous Solid Dispersion of Epigallocatechin Gallate for Enhanced Physical Stability and Controlled Release.

Epigallocatechin gallate (EGCG) has been recognized as the most prominent green tea extract due to its healthy influences. The high instability and low bioavailability, however, strongly limit its utilization in food and drug industries. This work, for the first time, develops amorphous solid dispersion of EGCG to enhance its bioavailability and physical stability. Four commonly used polymeric excipients are found to be compatible with EGCG in water-dioxane mixtures via a stepwise mixing method aided by vigorous mechanical interference. The dispersions are successfully generated by lyophilization. The physical stability of the dispersions is significantly improved compared to pure amorphous EGCG in stress condition (elevated temperature and relative humidity) and simulated gastrointestinal tract environment. From the drug release tests, one of the dispersions, EGCG-Soluplus® 50:50 (w/w) shows a dissolution profile that only 50% EGCG is released in the first 20 min, and the remains are slowly released in 24 h. This sustained release profile may open up new possibilities to increase EGCG bioavailability via extending its elimination time in plasma.

Fabrication and Characterizations of Hot-Melt Extruded Nanocomposites Based on Zinc Sulfate Monohydrate and Soluplus

Zinc sulfate monohydrate (ZnSO4)-loaded nanocomposites (NCs) were fabricated by using a hot-melt extruder (HME) system. Soluplus (SP) was adopted as an amphiphilic polymer matrix for HME processing. The micro-size of ZnSO4 dispersion was reduced to nano-size by HME processing with the use of SP. ZnSO4 could be homogeneously dispersed in SP through HME processing. ZnSO4/SP NCs with a 75 nm mean diameter, a 0.1 polydispersity index, and a −1 mV zeta potential value were prepared. The physicochemical properties of ZnSO4/SP NCs and the existence of SP in ZnSO4/SP NCs were further investigated by solid-state studies. Nano-size range of ZnSO4/SP NC dispersion was maintained in the simulated gastrointestinal environments (pH 1.2 and 6.8 media). No severe toxicity in intestinal epithelium after oral administration of ZnSO4/SP NCs (at 100 mg/kg dose of ZnSO4, single dosing) was observed in rats. These results imply that developed ZnSO4/SP NC can be used as a promising nano-sized zinc supplement formulation. In addition, developed HME technology can be widely applied to fabricate nanoformulations of inorganic materials.

Structural characteristics and prebiotic effects of Semen coicis resistant starches (type 3) prepared by different methods

In order to investigate the effects of different preparation methods on Semen coicis resistant starch, the structural properties and prebiotic effects of autoclaving treatment–purified S. coicis resistant starch (GP-SRS3), ultrasonic-autoclaving treatment–purified S. coicis resistant starch (UP-SRS3), enzyme-autoclaving treatment–purified S. coicis resistant starch (EP-SRS3) and microwave-moisture treatment–purified S. coicis resistant starch (MP-SRS3) were studied compared to high-amylose maize starch (HAMS). Fourier transform infrared spectroscopy and Solid-state 13C NMR spectroscopy showed all of SRS3 displayed B-type crystallite structure, furthermore, MP-SRS3 and UP-SRS3 showed higher degree of ordered structure and degree of double helical structure compared to other samples. Field emission scanning electron microscopy showed MP-SRS3 displayed deeply layered strips and UP-SRS3 exhibited some cavities. Moreover, S. coicis resistant starch could promote the growth of Bifidobacteria adolescentis better compared to high-amylose maize starch, among these samples. MP-SRS3 exhibited best prebiotic effect, which was possible attributed to its rough surface and double helix structure. B. adolescentis displayed a higher survival rate to the simulated gastrointestinal tract environment in SRS3 medium than that in high-amylose maize starch medium, especially MP-SRS3 and UP-SRS3, which partly contributed to its strips and cavities. Overall, MP-SRS3 could be regarded as a potential prebiotic to promote the growth of B. adolescentis for its structural trait.

Survival of probiotics in pea protein-alginate microcapsules with or without chitosan coating during storage and in a simulated gastrointestinal environment.

Pea protein-alginate microcapsules with or without a chitosan coating and containing Lactobacillus rhamnosus R0011 and L. helveticus R0052 were produced by extrusion and tested for survivability during storage and in an in vitro gastrointestinal environment. Both microcapsule formulations provided significant protection for cells incubated in synthetic stomach juice at 37°C for 2 h, followed by 3 h in simulated intestinal fluid, relative to non-encapsulated bacteria. However, evaluation of cell viability during 9 weeks of storage at room temperature revealed that chitosan coating significantly improved microcapsule performance compared to non-coated microcapsules. Refrigerated storage had no negative impact on the microcapsule protection ability of both types of microcapsules. Notably, chitosan-containing microcapsules showed much higher bacterial survival counts during challenge tests even after storage. Moreover, the addition of chitosan to the microcapsule formulation did not increase the microcapsule size.

Influence of dairy matrices on nutrient release in a simulated gastrointestinal environment

The objective of this study was to compare the kinetics of the release of nutrients (peptides and fatty acids) from different dairy matrices (milks, yogurts, and cheeses) in a simulated gastrointestinal environment. Prior to processing, different heat and homogenization treatments were applied to milks, and different drainage pH levels were used to control calcium concentration in cheeses. The dairy matrices were then subjected to simulated digestion. Matrix degradation, protein hydrolysis, and fat hydrolysis were analyzed during the gastric and intestinal digestion phases. Intense heat treatment of milk induced faster digestion of proteins in the gastric environment. Cheeses were more resistant to protein and lipid digestion than liquid or semi-solid matrices were. No direct relationship could be established between disintegration kinetics and cheese rheological properties. Fatty acid release in the intestinal phase was much faster when matrices were produced from homogenized milk. For cheeses, greater fatty acid release could not be related to faster matrix disintegration, suggesting that the lipid droplet size dispersion was more important than matrix breakdown was for the modulation of lipid digestion kinetics. Calcium soaps were produced in the intestinal environment, and their concentration was higher during the digestion of cheeses in comparison with milks and yogurts. These results suggest that processing-induced modifications to the composition, microstructure, and rheological properties of dairy matrices could be used to control nutrient delivery.

Adsorption of Lactobacillus acidophilus on attapulgite: Kinetics and thermodynamics and survival in simulated gastrointestinal conditions

In the present study, we investigated the optimum adsorption conditions, adsorption characteristics and surviva of Lactobacillus acidophilus adsorbed on attapulgite (ATT). Results of single factor experiments showed that the optimum adsorption parameters were ATT concentration of 10%, initial pH of 6.5 and temperature of 35 °C. From the static experiments of adsorption characteristics, we found that the experimental data were fitted best to the pseudo-secondorder kinetics and Langmuir isotherm models, and the adsorption was a spontaneous and endothermic process. Bacteria survival test showed that the microencapsulated L. acidophilus stored at −18 °C for 30 days achieved the highest survival rate (83.2% ± 5.8) and obtained better protection at simulated conditions of gastric pH and at high bile salt concentrations when compared with free bacteria. The study demonstrated that microencapsulation of L. acidophilus in ATT was an effective technique of protection against low-temperature injury and under simulated gastrointestinal environment.

Selection and evaluation of functional characteristics of autochthonous lactic acid bacteria isolated from traditional fermented stinky bean (Sataw-Dong)

The aim of this study was to evaluate the technological and functional potential of lactic acid bacteria (LAB) isolated from fermented stinky bean (Sataw-Dong). Of the 114 LAB colonies isolated from spontaneously fermented stinky bean which showed inhibitory activity against two food-borne pathogens (Staphylococcus aureus DMST 4480 and Escherichia coli DMST 4212), the five isolates (KJ03, KJ15, KJ17, KJ22, KJ23) exhibiting excellent antagonistic activity were subjected to further study. These five strains showed titratable acidity as lactic acid in the range of 1.47–1.55 %, with strains KJ03 and KJ23 additionally exhibiting a high NaCl tolerance of >7 % (w/v). Using 16S rRNA gene sequence analysis, strains KJ03 and KJ23 were identified as Lactobacillus plantarum and L. fermentum, respectively, and further investigated for their functional properties in vitro. Both strains survived well in a simulated gastrointestinal tract environment with 8 log CFU/ml). Lactobacillus plantarum KJ03 showed the best performance with respect to cholesterol removal (53 %), while L. fermentum KJ23 showed the highest cell-surface hydrophobicity (39.5 %). Neither of the two strains showed any hemolysis activity. Both strains hydrolyzed glycodeoxycholic and taurodeoxycholic acids. In terms of antibiotic susceptibility, L. fermentum KJ23 was not sensitive to tetracycline. Taking all of the results into account, L. plantarum KJ03 possessed desirable in vitro functional properties. This strain is therefore a good candidate for further investigation for use in Sataw-Dong fermentation to assess its technological performance as a potential probiotic starter.