Toxicity Assessment of Environmental Liquid Crystal Monomers: A Bacteriological Investigation on Escherichia coli and Staphylococcus epidermidis.

The widespread existence of liquid crystal monomers (LCMs) in various environmental matrices has been demonstrated, yet studies on the toxicological effects of LCMs are considerably scarce and are urgently needed to be conducted to assess the adverse impacts on ecology and human health. Here, we conducted a bacteriological study on two representative human commensal bacteria, Escherichia coli (E. coli) and Staphylococcus epidermidis (S. epidermidis), to investigate the effect of LCMs at human-relevant dosage and maximum environmental concentration on growth, metabolome, enzymatic activity, and mRNA expression. Microbial growth results exhibited that the highest inhibition ratio of LCMs on S. epidermidis reached 33.6% in our set concentration range, while the corresponding data on E. coli was only 14.3%. Additionally, LCMs showed more dose-dependent toxicity to S. epidermidis rather than E. coli. A novel in vivo solid-phase microextraction (SPME) fiber was applied to capture the in vivo metabolites of microorganisms. In vivo metabolomic analyses revealed that dysregulated fatty acid metabolism-related products of both bacteria accounted for >50% of the total number of differential substances, and the results also showed the species-specific and concentration-dependent metabolic dysregulation in LCM-exposed bacteria. The determination of enzymatic activity and mRNA relative expression levels related to oxidative stress confirmed our speculation that the adverse effects were related to the oxidative metabolism of fatty acids. This study complements the gaps in toxicity data for LCMs against bacteria and provides a new and important insight regarding metabolic dysregulation induced by environmental LCMs in human commensal bacteria.

Porphyromonas gingivalis regulates atherosclerosis through an immune pathway.

Atherosclerosis (AS) is a chronic inflammatory disease, involving a pathological process of endothelial dysfunction, lipid deposition, plaque rupture, and arterial occlusion, and is one of the leading causes of death in the world population. The progression of AS is closely associated with several inflammatory diseases, among which periodontitis has been shown to increase the risk of AS. Porphyromonas gingivalis (P. gingivalis), presenting in large numbers in subgingival plaque biofilms, is the "dominant flora" in periodontitis, and its multiple virulence factors are important in stimulating host immunity. Therefore, it is significant to elucidate the potential mechanism and association between P. gingivalis and AS to prevent and treat AS. By summarizing the existing studies, we found that P. gingivalis promotes the progression of AS through multiple immune pathways. P. gingivalis can escape host immune clearance and, in various forms, circulate with blood and lymph and colonize arterial vessel walls, directly inducing local inflammation in blood vessels. It also induces the production of systemic inflammatory mediators and autoimmune antibodies, disrupts the serum lipid profile, and thus promotes the progression of AS. In this paper, we summarize the recent evidence (including clinical studies and animal studies) on the correlation between P. gingivalis and AS, and describe the specific immune mechanisms by which P. gingivalis promotes AS progression from three aspects (immune escape, blood circulation, and lymphatic circulation), providing new insights into the prevention and treatment of AS by suppressing periodontal pathogenic bacteria.

Tetrazolyl Porphyrin-Based Hydrogen-Bonded Organic Frameworks: Active Sites-Mediated Host-Guest Synergy for Advanced Antimicrobial Applications.

Hydrogen-bonded organic frameworks (HOFs) with multiple functions and permanent pores have received widespread attention due to their potential applications in gas adsorption/separation, drug delivery, photocatalysis, proton conduction, and other fields. Herein, we constructed a three-dimensional (3D) HOF with 1D square channels by utilizing a dual-functional tetrazolyl porphyrin ligand bearing an active center of the porphyrin core and open sites of nitrogen atoms through π-π stacking and hydrogen-bonding interaction self-assembly. The structure exhibits both solvent resistance and thermal stability, and especially, maintains these after being transformed into nanoparticles. Meanwhile, the active sites exposed on the inner wall of the pores can interact well with the photoactive cationic dye molecules to form an effective host-guest (H-G) system, which can realize boosted photosensitized singlet oxygen (1O2) production under red light irradiation and synergistic sterilization toward Staphylococcus aureus (S. aureus) with an inhibition ratio as high as 99.9%. This work provides a valuable design concept for HOF-related systems in pursuit of promoted photoactivity.

Fabrication and structural properties of water-dispersible phytosterol using hot melt extrusion.

Hot-melt extrusion (HME) technology was employed to improve water dispersibility of phytosterol (P) using glycerol (G), lecithin (L), and gum arabic (A) as emulsifiers and stabilizers. The structural properties and water dispersibility of HME products were investigated. In contrast to physical mixtures, better water dispersibility and storage stability were observed for HME products, especially P:L:G:A extrudate. These improvements may be mainly associated with decreased crystallinity of phytosterol due to the occurrence of co-crystallization of phytosterol with glycerol during HME process, as confirmed by DSC and XRD data. In addition, HME-induced lecithin-arabic gum reaction products effectively stabilize phytosterol microparticle in aqueous dispersion by providing a steric hindrance. These results suggest that HME could be an effectively and potentially solvent-free technique to produce water-dispersible phytosterol on a large scale.

Enzyme-Adsorbed Chitosan Nanogel Particles as Edible Pickering Interfacial Biocatalysts and Lipase-Responsive Phase Inversion of Emulsions.

Here, a simple food-grade Pickering emulsion system is prepared and adopted for biphasic biocatalytic reactions. The chitosan nanogels were prepared with strong dispersion of chitosan aggregates approaching neutral pH and then used as the particle emulsifiers to produce oil-in-water Pickering emulsions. The chitosan nanogel exhibited high affinity to negatively charged lipase. As a result of increasing the biphasic interfacial area and loading amount on the oil-water interface, the catalysis activity of lipase and recycling and pH stability were highly enhanced through colorimetric determination of p-nitrophenol (the hydrolysis product of p-nitrophenyl palmitate). A general strategy was proposed to obtain stimulus-responsive Pickering emulsions that can undergo phase inversion. The in situ modification of the wettability of chitosan nanogel could be attributed to the interaction between nanogel and free fatty acids, which was triggered by lipase hydrolysis. This would permit a rapid and controlled release of hydrophobic active components in response to enzymatic triggers.

Preparation and characterization of a novel colorimetric indicator film based on gelatin/polyvinyl alcohol incorporating mulberry anthocyanin extracts for monitoring fish freshness.

This work aimed to develop a novel colorimetric indicator film for monitoring of food freshness based on gelatin/polyvinyl alcohol matrix incorporated with anthocyanin extracts from mulberry. The color of anthocyanin extracts solutions obviously changed from bright red to dark green in the pH range of 2.0-11.0. FTIR spectra and isothermal titration calorimetry showed that the anthocyanin extracts were successfully combined with gelatin/polyvinyl alcohol matrix by hydrogen binding and electrostatic interaction, which enhanced the stability of anthocyanin. The scanning electric microscopy showed that the compatibility between polyvinyl alcohol and gelatin were improved owing to the addition of anthocyanin extracts. With the anthocyanin extracts addition from 0 to 45 mg/100 mL mixed solution, the tensile strength decreased from 30.80 to 21.01 MPa and the elongation at break increased from 589.22% to 905.86%. The color response of film in buffer solution of different pH were in accordance with anthocyanin extracts solutions, and its color changes were clearly visible with naked eye. Finally, the film was evaluated by a test on monitoring fish spoilage, which presented visible color changes due to volatile nitrogenous compounds formed over time. These results showed that this developed film could be used as an effective method for the monitoring of food freshness.

One-step formation of a double Pickering emulsion via modulation of the oil phase composition.

There are two long-standing issues that are holding back the full exploitation of food-based double emulsions: (i) unavailability of large-scale equipment to ensure efficient nondestructive two-step emulsification and (ii) limited food-grade ingredients available to replace polyglycerol polyricinoleate (PGPR) as the primary emulsifier. To overcome these, a facile one-step emulsification strategy was developed to generate a food-grade W/O/W double Pickering emulsion by using corn-peptide-functionalized calcium phosphate (CP-CaP) particles as the emulsifier. It was demonstrated that the wettability of such CP-CaP particles can be tuned through modulation of the oil phase composition. The incorporation of health benefiting ω-3 oils (algal oil) or essential polyunsaturated fatty acids (linoleic acid and linolenic acid) into common vegetable oils leads to the hydrophobization of a fraction of CP-CaP particles through in situ adsorption of the free fatty acids, which provide satisfactory stabilization of both O/W and W/O interfaces, thus generating stable double Pickering emulsions. Moreover, the algal oil-loaded double Pickering emulsions that incorporate water-soluble isoascorbic acid show improvement in both their oxidative stability and flavor properties. This study demonstrated that the edible CP-CaP particle based double Pickering emulsions have promising potential to be applied in the food industry.

Interaction of Soybean 7S Globulin Peptide with Cell Membrane Model via Isothermal Titration Calorimetry, Quartz Crystal Microbalance with Dissipation, and Langmuir Monolayer Study.

To understand the underlying molecular mechanism of the cholesterol-lowering effect of soybean 7S globulins, the interactions of their pepsin-released peptides (7S-peptides) with cell membrane models consisting of dipalmitoylphosphatidylcholine (DPPC), dioleoylphosphatidylcholine (DOPC), and cholesterol (CHOL) were systematically studied. The results showed that 7S-peptides were bound to DPPC/DOPC/CHOL liposomes mainly through van der Waals forces and hydrogen bonds, and the presence of higher CHOL concentrations enhanced the binding affinity (e.g., DPPC/DOPC/CHOL = 1:1:0, binding ratio = 0.114; DPPC/DOPC/CHOL = 1:1:1, binding ratio = 2.02). Compression isotherms indicated that the incorporation of 7S-peptides increased the DPPC/DOPC/CHOL monolayer fluidity and the lipid raft size. The presence of CHOL accelerated the 7S-peptide accumulation on lipid rafts, which could serve as platforms for peptides to develop into ß-sheet rich structures. These results allow us to hypothesize that 7S-peptides may indirectly influence membrane protein functions via altering the membrane organization in the enterocytes.

Quillaja saponin-based hollow salt particles as solid carriers for enhancing sensory aroma with reduced sodium intake.

Dietary salt is a vital ingredient associated with sensory performance in processed foods, while reduced salt intake linked to public health is highly desired by consumers and food manufacturers. In this paper, quillaja saponin (QS) based hollow salt particles (∼10 µm) were fabricated by simple spray drying, and utilized as solid carriers to enhance sensory aromas with reduced sodium intake. QS-coated nanodroplets were firstly prepared as a reservoir for flavor oils (lemon and garlic oil), and then served as frameworks to construct hollow salt particles via general spray drying. Headspace gas chromatography-mass spectrometry (DHS-GC-MS) and panel sensory analysis conclude that the hollow salt particles loaded with flavor oils enhance typical aroma attributes and saltiness perception in comparison with their mixture control. The QS-based hollow salt particles could be developed into novel vehicles for improving flavor performance with reduced sodium intake, and furthermore used for delivery of hydrophobic bioactives in food systems.

Analysis using fluorescence labeling and mass spectrometry of disulfide-mediated interactions of soy protein when heated.

It is well-known that disulfide-mediated interactions are important when soy protein is heated, in which soy proteins are dissociated and rearranged to some new forms. In this study, the disulfide bond (SS) linked polymer, which was composed of the acidic (A) polypeptides of glycinin, basic (B) polypeptides of glycinin, and a small amount of α' and α of ß-conglycinin, was formed as the major product, accompanied by the formation of SS-linked dimer of B and monomer of A as minor products. The role of sulfhydryl (SH) of different subunits/polypeptides for forming intermolecular SS was investigated. The SH of B in glycinin (Cys298 of G1, Cys289 of G2, Cys440 of G4) was transformed into SS in polymer identified by mass spectrometry analysis. The SH content of polymer was lower than that of glycinin and ß-conglycinin subunits when heated. The SH content of B in polymer was lower than that in glycinin subunit, and both of them were decreased by heating. The SH content of A in polymer was increased and higher than that of B in polymer and A in glycinin subunit when heated. These results indicated that the SH of B in glycinin subunit was subjected to not only SH oxidation but also SH-SS exchange (with SS of A) for forming intermolecular SS of polymer. The SH oxidation and SH-SS exchange were proven by the change of SH content for the first time. The SH of B was suggested to be reactive for forming intermolecular SS of polymer.

Heat-induced aggregation and sulphydryl/disulphide reaction products of soy protein with different sulphydryl contents.

In this study, soy proteins were reduced with 0.1-10mM dithiothreitol (DTT) to obtain an increasing number of sulphydryl groups (SH) with a similar particle size. Aggregation was promoted by increasing the degree of reduction when heated (100°C, 30min), resulting in larger sized aggregates (from 40 to 70nm) and a higher viscosity of the aggregate dispersion. The disulphide bond (SS) content decreased and the less SS linked polymer, which was composed of acidic (A) polypeptide of glycinin, basic (B) polypeptides of glycinin, and a small amount of α' and α subunits of ß-conglycinin, was formed with increasing reduction degree, suggesting that SH/SS polymerisation was not the driving force for aggregation. The larger aggregates with increasing degrees of reduction were composed of more B of glycinin and ß of ß-conglycinin, suggesting that the A and the small amount of α' and α in the SS linked polymer have an inhibiting effect on protein aggregates formation.

Comparative studies on sulfhydryl determination of soy protein using two aromatic disulfide reagents and two fluorescent reagents.

In this study, the sulfhydryl (SH) contents of unheated and heated (90 °C, 5 min) soy protein were detected under different conditions (pH, reagent addition order, SDS/GuHCl concentration, EDTA) using two aromatic disulfide reagents: 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) and 4,4'-dithiodipyridine (DPS). Two fluorescent alkylating reagents, monobromobimane (mBBr) and N-(1-pyrenyl)maleimide (NPM), were chosen due to their high sensitivity and were also used. Amino acid analysis was used to detect the SH (cysteine) contents of unheated (7.51 ± 0.45 µmol SH/g protein) and heated (1.47 ± 0.10 µmol SH/g protein) soy protein, and similar results were obtained using enzymatic hydrolysis-assisted DPS. The SH content detected by DTNB was affected by pH, denaturant species, and denaturant concentration, and the best results were obtained at pH 7.0 when 6 M GuHCl was added after DTNB. These results were lower than that of the amino acid analysis, however. The SH detected by DPS was not as affected as that of DTNB by pH, denaturant species, and denaturant concentration. Additionally, the results of the amino acid analysis were similar to that of DPS at pH 7.0 in 2% SDS and 4-6 M GuHCl when SDS and GuHCl were added after DPS. EDTA did not have a significant effect on SH detection when DTNB and DPS were added before SDS and GuHCl. Finally, although mBBr and NPM can detect SH in low protein concentrations ((1)/10 of that required for DTNB and DPS), mBBr and NPM overestimated the SH content of soy protein. Therefore, using DPS at pH 7.0 when it is added before SDS and GuHCl is the most reliable method for detecting the SH content of soy protein.