Lactic acid bacteria modulate the gastrointestinal digestive behavior of soy glycinin and correlation with its immunoreactivity: a peptidomic study.

Lactic acid bacterial fermentation helps reduce the immunoreactivity of soy protein. Nevertheless, the effect of lactic acid bacterial fermentation on a particular soy allergen and the consequent dynamic change of epitopes during gastrointestinal digestion are unclear. In this study, soy glycinin was isolated and an in vitro dynamic gastrointestinal model was established to investigate the dynamic change in the immunoreactivity and peptide profile of unfermented (UG) and fermented glycinin (FG) digestates. The results demonstrated that the FG intestinal digestate had a lower antigenicity (0.08%-0.12%) and IgE-binding capacity (1.49%-3.61%) towards glycinin at the early (I-5) and middle (I-30) stages of gastrointestinal digestion, especially those prepared at 2% (w/v) protein concentration. Peptidomic analysis showed that the glycinin subunits G1 and G2 were the preferred ones to release the most abundant peptides, whereas G2, G4, and G5 had an elevated epitope-cleavage rate in FG at stages I-5 and I-30. Three-dimensional modeling revealed that fermentation-induced differential degradation epitopes in gastrointestinal digestion were predominantly located in the α-helix and ß-sheet structures. They were closely correlated with the reduced immunoreactivity of soy glycinin.

Digestive characteristics of extracellular polysaccharide from Lactiplantibacillus plantarum T1 and its regulation of intestinal microbiota.

This study assessed the potential prebiotic characteristics of the previously reported Lactiplantibacillus plantarum extracellular polysaccharide (EPS-T1) with immunological activity. EPS-T1 was a novel heteropolysaccharide composed of glucose and galactose (1.00:1.21), with a molecular weight of 1.41 × 106 Da. The monosaccharide composition, molecular weight, fourier transform infrared, and 1H NMR analysis showed that EPS-T1 was well tolerated in the simulated oral cavity, gastric fluid, and small intestinal fluid environments, and was not easily degraded. Meanwhile, EPS-T1 could effectively be used as a carbon source to promote the growth of beneficial Lactobacillus species (Lactobacillus delbrueckii ssp. Bulgaricus, Streptococcus thermophilus, Lacticaseibacillus rhamnose GG, Lactiplantibacillus plantarum, Lacticaseibacillus paracasei and Lactobacillus reuteri). After 24 h of fecal fermentation, EPS-T1(5 mg/mL) effectively reduced the relative abundance of harmful bacteria such as the Escherichia-Shigella, Citrobacter, Fusobacterium, Parasutterella, and Lachnoclostridium. While, the level content of beneficial flora (Bacteroides, Blautia, Phascolarctobacterium, Bifidobacterium, Parabacteroides, and Subdoligranulum) were significantly increased. In addition, EPS-T1 was able to significantly promote the enrichment of short-chain fatty acids such as acetic acid, propionic acid and butyric acid. These results provide some basis for the functional application of EPS-T1 as a potential prebiotic.

Effects of Lacticaseibacillus paracasei SNB-derived postbiotic components on intestinal barrier dysfunction and composition of gut microbiota.

The bacterial surface components are considered as effector molecules and show the potential to support intestinal health, but the detailed mechanism of how the gut microbiota changes after the intervention of surface molecules is still unknown. In the present study, capsular polysaccharide (B-CPS) and surface layer protein (B-SLP) were extracted from Lacticaseibacillus paracasei S-NB. The protective effect of direct administration of B-CPS (100 µg/mL) and B-SLP (100 µg/mL) on intestinal epithelial barrier dysfunction was verified based on the LPS-induced Caco-2 cell model. Additionally, the B-CPS and B-SLP could be utilized as carbon source and nitrogen source for the growth of several Lactobacillus strains, respectively. The postbiotic potential of B-CPS and B-SLP was further evaluated by in vitro fermentation with fecal cultures. The B-CPS and a combination of B-CPS and B-SLP regulated the composition of gut microbiota by increasing the relative abundances of Bacteroides, Bifidobacterium, Phascolarctobacterium, Parabacteroides, Subdoligranulum and Collinsella and decreasing the abundance of pathogenic bacteria like Escherichia-Shigella, Blautia, Citrobacter and Fusobacterium. Meanwhile, the total short-chain fatty acid production markedly increased after fermentation with either B-CPS individually or in combination with B-SLP. These results provided an important basis for the application of B-CPS and B-SLP as postbiotics to improve human intestinal health.

Roles of luxS in regulation of probiotic characteristics and inhibition of pathogens in Lacticaseibacillus paracasei S-NB.

Lactic acid bacteria (LAB) have excellent tolerance to the gastrointestinal environment and high adhesion ability to intestinal epithelial cells, which could be closely related to the LuxS/AI-2 Quorum sensing (QS) system. Here, the crucial enzymes involved in the synthesis of AI-2 was analyzed in Lacticaseibacillus paracasei S-NB, and the luxS deletion mutant was constructed by homologous recombination based on the Cre-lox system. Afterwards, the effect of luxS gene on the probiotic activities in L. paracasei S-NB was investigated. Notably, the tolerance of simulated gastrointestinal digestion, AI-2 production, ability of auto-aggregation and biofilm formation significantly decreased (p < 0.05 for all) in the S-NB△luxS mutant. Compared to the wild-type S-NB, the degree of reduction in the relative transcriptional level of the biofilm -related genes in Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923 was diminished when co-cultured with S-NB△luxS. Furthermore, the inhibitory effect of S-NB△luxS on the adhesion (competition, exclusion and displacement) of E. coli ATCC 25922 and S. aureus ATCC 25923 to Caco-2 cells markedly decreased. Therefore, comprehensive analysis of the role by luxS provides an insight into the LuxS/AI-2 QS system of L. paracasei S-NB in the regulation of strain characteristics and inhibition of pathogens.

The interaction among Kluyveromyces marxianus G-Y4, Lacticaseibacillus paracasei GL1, and Lactobacillus helveticus SNA12 and signaling molecule AI-2 participate in the formation of biofilm.

In this study, two strains of lactic acid bacteria (Lacticaseibacillus paracasei GL1 and Lactobacillus helveticus SNA12) and one yeast strain of Kluyveromyces marxianus G-Y4 (G-Y4) isolated from Tibetan kefir grains were co-cultured. It was found that the addition of G-Y4 could not only promote the growth of lactic acid bacteria, but also increase the release of metabolites (lactic acid, ethanol, and amino nitrogen). Furthermore, the addition of live cells and cell-free fermentation supernatant (CFS) of G-Y4 could increase the ability of biofilm formation. Morever, the surface characteristics results showed that the addition of G-Y4 live cells could enhance the aggregation ability and hydrophobicity of LAB. Meanwhile, adding live cells and CFS of G-Y4 could promote the release of signaling molecule AI-2 and enhance the expression of the LuxS gene related to biofilm formation. In addition, Fourier-transform infrared spectroscopy and chemical composition analysis were used to investigate the composition of the biofilm, and the results indicated that the biofilm was mainly composed of a small amount of protein but it was rich in polysaccharides including glucose, galactose, and mannose with different ratios. Finally, the formation of biofilm could delay the decline of the number of viable bacteria in storage fermented milk.

Optimization of Wall Material of Freeze-Dried High-Bioactive Microcapsules with Yellow Onion Rejects Using Simplex Centroid Mixture Design Approach Based on Whey Protein Isolate, Pectin, and Sodium Caseinate as Incorporated Variables.

For the food sector, onion rejects are an appealing source of value-added byproducts. Bioactive compounds were recovered from yellow onion rejects using a pulse electric field process at 6000 v and 60 pulses. The onion extract was encapsulated with whey protein isolate (WPI), pectin (P), and sodium caseinate (SC) with a mass ratio of 1:5 (extract/wall material, w/w). A Simplex lattice with augmented axial points in the mixture design was applied for the optimization of wall material for the encapsulation of onion reject extract by freeze-drying (FD). The optimal wall materials were 47.6 g/100 g (SC), 10.0 g/100 g (P), and 42.4 g/100 g (WPI), with encapsulation yield (EY) of 85.1%, total phenolic content (TPC) of 48.7 mg gallic acid equivalent/g DW, total flavonoid content (TFC) of 92.0 mg quercetin equivalent/g DW, and DPPH capacity of 76.1%, respectively. The morphological properties of the optimal encapsulate demonstrated spherical particles with a rough surface. At optimal conditions, the minimum inhibitory concentration (MIC) of the extract (mean diameter of inhibition zone: 18.8 mm) was shown as antifungal activity against Aspergillus niger.

Assessment of In Vitro Digestive Behavior of Lactic-Acid-Bacteria Fermented Soy Proteins: A Study Comparing Colloidal Solutions and Curds.

This study investigated the effect of lactic-acid-bacteria fermentation on the microstructure and gastrointestinal digestibility of soy proteins using a digestomics approach. Fermented soy protein isolates (FSPIs) under varied fermentation-terminal pH demonstrated a colloidal solution (FSPI-7.0/6.0) or yogurt-like curd (FSPI-5.0/4.0) state. Cryo-electron microscopy figures demonstrated the loosely stacked layer of FSPI-7.0/6.0 samples, whereas a denser gel network was observed for FSPI-5.0/4.0 samples. Molecular interactions shifted from dominant ionic bonds to hydrophobic forces and disulfide bonds. The gastric/intestinal digestion demonstrated that the curd samples afforded a significantly low particle size and high-soluble protein and peptide contents in the medium and late digestive phases. A peptidomics study showed that the FSPI-6.0 digestate at early intestinal digestion had a high peptidome abundance, whereas FSPI curd digestates (FSPI-5.0/4.0) elicited a postponed but more extensive promotion during medium and late digestion. Glycinin G2/G4 and ß-conglycinin α/α' subunits were the major subunits promoted by FSPI-curds. The spatial structures of glycinin G2 and ß-conglycinin α subunits demonstrated variations located in seven regions. Glycinin G2 region 6 (A349-K356) and ß-conglycinin α subunit region 7 (E556-E575), which were located at the interior of the 3D structure, were the key regions contributing to discrepancies at the late stage.

Optimization of ultrasonic-assisted extraction of astaxanthin from green tiger (Penaeus semisulcatus) shrimp shell.

This study was aimed at optimizing the astaxanthin extraction efficiency from shrimp shell (green tiger, Penaeus semisulcatus). Astaxanthin was extracted using selected nonpolar/polar solvents (petroleum ether, n-hexane, ethanol, acetone) individually and in ternary mixtures of petroleum ether, acetone, and water in ratios of 15:50:35, 50:45:5, and 15:75:10 for different times (2,4 and 6 h). The results showed that solvents with higher polarity were more suitable for the extraction of astaxanthin, and increasing the extraction time from 2 to 6 h improved the extraction yield. The conditions of extraction of astaxanthin with the desirable solvent were then optimized with the ultrasonic method using the Box-Behnken design [variables included: extraction temperature (25 to 45 °C), extraction time (5 to 15 min), and ultrasound amplitude (20 to 100%)]. Optimal extraction conditions were determined as the ultrasonic amplitude of 23.6%, extraction time of 13.9 min, and extraction temperature of 26.3 °C. Under this optimum condition, the amount of astaxanthin, ferric reducing antioxidant power, and free radical scavenging capacity of the extract were obtained as 51.5%, 1705 µmol of Fe2+/g, and 73.9%, respectively. Extraction and analysis of the extract at the optimum point were used to validate the results.

Effect of lactic fermentation on soy protein digestive pattern assessed by an in vitro dynamic gastrointestinal digestion model and the influence on human faecal microbiota.

BACKGROUND: The aim of this study was to investigate the effect of lactic fermentation on soy protein gastrointestinal digestive pattern and the influence of protein digesta on human faecal microbiota. Soymilk and soy yogurt were prepared in this study and a novel in vitro dynamic gastrointestinal model was employed to simulate gastric and duodenum digestions. Particle size, sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE), and peptide content were monitored at the end of duodenum tract. RESULTS: Ingestion of soy yogurt allowed a rapid drop in pH from 7.0 to 5.0 at simulated duodenal digestion (0-30 min), and resulted in a loss in soluble protein content compared to that of soymilk. The electrophoretic pattern between soymilk and soy yogurt exerted distinctive differences at early stages of duodenal digestion (0-60 min) and resulted in different peptide contents (180 min). Soy yogurt duodenal digesta collected at 180 min (D180), by co-fermentation with human intestinal flora distribution, allowed a higher population in Bifidobacterium spp., Lactobacillus/Enterococcus spp. and Streptococcus/Lactococcus spp., whereas soy yogurt D30 resulted in lower population in Clostridium and Escherichia coli compared to samples co-fermented with soymilk digesta. CONCLUSION: The results demonstrated lactic fermentation of soy protein modulated human intestinal microflora and might relate to the different protein digestive behaviours. © 2020 Society of Chemical Industry.

Effect of microencapsulation on antioxidant and antifungal properties of aqueous extract of pomegranate peel.

The aqueous extract of pomegranate (Punica granatum L.) peel compounds was freeze-dried (FDPOPx) and encapsulated using two wall forming components at two concentrations (maltodextrin: MDX and ß-cyclodextrin: ßCDX; 5 and 10%) with a mass ratio of 1:5 (extract/wall material). Different properties of the encapsulated powders (bioactive components, physicochemical and morphological properties) and storage stability of prepared microcapsules were evaluated during 42 days of storage at a different relative humidity (52 and 75%) and temperatures (4 and 25 °C). Encapsulated powder with ßCDX-10% had the highest total phenolic compounds (TPC: 58.78 mg GA/g) and antioxidant capacity [FRAP: 1414.76 µmol Fe2+/g and DPPH assay (RSA): 77.83%] among other wall materials. The amounts of TPC and their antioxidant capacity decreased during the 42 days of storage. However, the highest TPC was observed in the freeze-dried MDX-10%  % encapsulated powder at 4 °C storage temperature and 52% relative humidity with a half-life (t1/2) of 81 days, the reaction rate constant (k) of 0.85 × 10-2 min-1 and the glass transition temperature of 69.73 °C. In addition, the polyphenolic extracts (both free and encapsulated) were able to control the growth of yeasts and molds, and maintaining the sensory properties of cupcakes as the model food system. The lowest growth after 9 days of storage of cupcake was observed in samples prepared with 1.5% of microencapsulated powder (MDX-10%) which was equivalent to the effect of the chemical preservative potassium sorbate.

Effects of different satiety levels on the fate of soymilk protein in gastrointestinal digestion and antigenicity assessed by an in vitro dynamic gastrointestinal model.

This study was designed to compare the effects of different satiety levels on the digestion and antigenicity of soymilk protein. The DIVRSD-II dynamic in vitro digestion model (DIVD) was employed to simulate different satiety degrees by changing the amount of food intake, namely full satiety (DIVD-FS), semi-satiety (DIVD-SS) and limited-satiety (DIVD-LS). A standardized static in vitro digestion method (SIVD) was used as a reference. Coupled with 60 min of gastric digestion and 120 min of intestinal digestion, the pH, particle size, soluble protein content, peptide content, gel electrophoresis, and antigenicity of soymilk digesta were monitored. The results showed that different satiety degrees altered soymilk protein digestive patterns in terms of gastric transit time, hydrolysis degree and antigenicity. The results of soluble protein content suggested that soymilk protein in DIVD-FS showed faster gastric transition than DIVD-SS and DIVD-LS. Gel electrophoresis and peptide content indicated that DIVD-FS digesta showed predominantly lower hydrolysis degrees in gastric and early intestinal stages. This further led to the persistence of major allergens at the early stage of intestinal digestion for DIVD-FS digesta. Soymilk protein digested using SIVD showed mostly intermediate values which indicated a good reference to the different satiety degrees of DIVD, although a descriptive result was obtained at early intestinal digestion. The results of this study showed for the first time the effect of different satiety degrees on hydrolysis kinetics, digestive degree and antigenicity of soy protein. The results suggested that the knowledge-base of soy protein digestibility depends on different satiety degrees and will be useful for guiding a healthy diet mode.