Qilin Huang

Structure, molecular conformation, and immunomodulatory activity of four polysaccharide fractions from Lignosus rhinocerotis sclerotia

Four polysaccharide fractions, LRP-1, LRP-2, LRP-3 and LRP-4 were extracted stepwise from Lignosus rhinocerotis sclerotia with distilled water at 25, 95, 120°C and 1.0M NaOH solution at 4°C. Their structure, molecular size and chain conformation were clarified using SEC-MALLS-RI, GC, FT-IR and UV-vis. Furthermore, their immunomodulatory activities were evaluated by the model of cyclophosphamide (Cy)-induced immunosuppression. The LRP-1 and LRP-2 were polysaccharide-protein complexes (46-68% β-d-glucan and 27-48% protein), while LRP-3 and LRP-4 were absolutely composed of β-d-glucose. The LRP-4 with low polydispersity had much higher molecular weight (Mw, 5.86×106g/mol) and intrinsic viscosity ([η], 202.6ml/g) than other LRP fractions. Based on Mw, radius of gyration (z1/2) and [η] data with the exponent β of z1/2-Mw and its U-shaped curve, all four LRP fractions were highly branched macromolecules and LRP-3 showed a more compact sphere-like conformation than LRP-2 in aqueous solution. Additionally, all four LRP fractions exhibited protective effects against Cy-induced immunosuppression in mice by improving immune organs as well as stimulating the release of major cytokines TNF-α and INF-γ. This work provides a theoretical basis for the application of polysaccharides and their protein complexes from Lignosus rhinocerotis sclerotia in food- or drug-based therapies.

A comb-like branched β-d-glucan produced by a Cordyceps sinensis fungus and its protective effect against cyclophosphamide-induced immunosuppression in mice

An exopolysaccharide (EPS) was fractionated from fermentation media of a Cordyceps sinensis fungus (Cs-HK1) by ethanol precipitation at 2/5 volume ratio of ethanol/media. Its structural characteristics were elucidated by FT-IR, GC, GC-MS, 1D and 2D NMR combined with periodate oxidation, Smith degradation, partial acid hydrolysis, and methylation analysis. Furthermore, the immunomodulatory activity of EPS was evaluated by the model of cyclophosphamide-induced immunosuppression. The results from monosaccharide composition and partial acid hydrolysis indicated that EPS almost consisted of glucose excluding a trace amount of mannose. GC-MS and NMR analysis further confirmed EPS had a linear backbone of (1→3)-β-D-glucopyranosyl residues with a single (1→6)-β-D-glucopyranosyl side-branching unit for every three β-D-glucopyranosyl residues, showing a comb-like β-D-glucan with short and intensive branches, which was responsible for high viscosity. Moreover, EPS could significantly enhance immune organs and stimulate the release of major cytokines TNF-α and INF-γ, suggesting that EPS exhibited protective effect in immunocompromised mice.

Construction of a Cordyceps sinensis exopolysaccharide-conjugated selenium nanoparticles and enhancement of their antioxidant activities

A Cordyceps sinensis exopolysaccharide (EPS)-conjugated selenium nanoparticles (SeNPs) were successfully constructed through the reduction of SeO32-. The EPS-SeNPs were characterized in terms of formation, morphology, size, Se distribution and phase by UV-vis, FT-IR, transmission electron microscopy (TEM), dynamic light scattering (DLS), energy dispersive X-ray (EDX) and wide angle X-ray diffraction (WAXD) measurements. Results revealed that the SeNPs conjugated to EPS were amorphous and could be well dispersed at a size range of 80-125nm. The interactions between the OH groups of EPS and SeNPs substituted for intermolecular interaction in native EPS to form new CO⋯Se bonds, resulting in good dispersion of SeNPs in the EPS matrix. Besides, the EPS-SeNPs at different Se/P ratios exhibited significant scavenging ability on superoxide anion radical (O2-) and ABTS radical cation (ABTS+) when compared to pure EPS, indicating that the conjugated SeNPs reinforced antioxidant effect of EPS. This work not only provides a simple and efficient way to construct well-dispersed SeNPs in aqueous system, and demonstrates the vital role of the EPS as a biopolymer template for dispersion, stabilization and size control of SeNPs, but also finds the EPS-SeNPs can potentially serve as a good antioxidant towards O2- and ABTS+.

Gel characteristics and microstructure of fish myofibrillar protein/cassava starch composites

The changes in fish myofibrillar protein/cassava starch composites in the starch fraction range from 0 to 1, with their total content maintained at 60mg/mL, were investigated in terms of textural properties, rheological behaviours, morphology, spatial distribution and protein molecular structure. The results revealed that the starch fraction of 0.5 was a critical point for the conversion of the protein matrix to starch matrix and conversion of the gel from elastic to weak. Moreover, the protein-starch synergistic effect on the storage modulus was strongest at fractions of 0.5 and 0.6, due to the formation of a semi-interpenetrating network, with more amylose from the melted starch granules interpenetrated with the protein molecules, and the absorption of water by the starch granules to concentrate the protein matrix. Additionally, no covalent interaction between the protein and starch occurred with increasing starch fraction, thus having no significant influence on the protein secondary structure.

A hyperbranched β-D-glucan with compact coil conformation from Lignosus rhinocerotis sclerotia

An alkali-soluble polysaccharide was extracted from Lignosus rhinocerotis sclerotia (LRP). Its structural characteristics were determined by GC-MS, FT-IR, GC, 1D and 2D NMR combined with Smith degradation and methylation analysis. The LRP had a (1→3)-β-d-Glcp backbone with every three residues bearing a (1→6)-linked and hyperbranched side chain that contained three (1→6)-β-d-Glcp residues as secondary main chain and two terminal β-d-Glcp residues linked at O3. The degree of branching was 0.76 from GC-MS analysis, implying a highly branched structure for LRP. The Mw, z1/2, Rh and [η] values of LRP in 0.25M LiCl/DMSO were measured by SEC-MALLS-Vis-RI combination technology to be 2.88×105g/mol, 30.36nm, 22.34nm and 131.50ml/g, respectively. Furthermore, the exponent α of [η]-Mw, β of z1/2-Mw, the fractal dimension df and molecular parameter ρ were determined to be 0.20, 0.33, 2.50 and 1.36, demonstrating that the LRP was a hyperbranched polysaccharide and adopted a compact coil conformation in LiCl/DMSO.

Chemical structure and antioxidant activity of the biomacromolecules from paddlefish cartilage.

To evaluate the effect of extraction methods on chemical structure and association with antioxidant activity of the extracts from paddlefish cartilage, the three extracts (EXT-A, EXT-B and EXT-C) were obtained from the cartilage by signal alkali extraction, microwave-assisted alkali extraction, and microwave-assisted alkali extraction followed by Sevags deproteinization, respectively. Chemical structures of the polymer were investigated by GPC (Gel Permeation Chromatography), FT-IR, GC and amino acid analysis. The results indicated that both EXT-A and EXT-B consisted of polysaccharide and protein, but the protein content of EXT-B (87.9%) was significantly higher than EXT-A (22.3%). Meanwhile EXT-C was polysaccharide composed of glucose, galactose, D-glucuronic acid and xylose. EXT-B extracted by microwave-assisted alkali method, containing dominant protein and rich in tyrosine, glycine and glutamic acid, exhibited obviously higher antioxidant activity than those of the extracts by other methods. The results indicated that microwave-assisted alkali extraction was favorable for protein dissolving out of cartilage, and protein content and composition of the extracts play important roles in antioxidant activity.

Effect of ultrasound on size, morphology, stability and antioxidant activity of selenium nanoparticles dispersed by a hyperbranched polysaccharide from Lignosus rhinocerotis

The differences between ultrasonic and non-ultrasonic approaches in synthesizing Lignosus rhinocerotis polysaccharide-selenium nanoparticles (LRP-SeNPs) were compared in terms of size, morphology, stability and antioxidant activity by UV-VIS, FT-IR, X-ray diffraction (XRD), dynamic light scattering (DLS), transmission electron microscopy (TEM), and energy dispersive X-ray (EDX) with high resolution TEM. Results indicated that the SeNPs were associated with the LRP macromolecules in a physical adsorption pattern without breaking chemical bonds, and the ultrasonic treatment reduced the size of SeNPs, narrowed the size distribution as well as improved the stability. Due to the LRP compact coil structure loosed under ultrasonic cavitation, the SeNPs could be easily diffused into the LRP internal branches instead of gathering on the LRP surface and were well dispersed and eventually stabilized throughout the extended branches. After ultrasound treatment, the SeNPs had a minimum average diameter of ∼50 nm and the LRP-SeNPs could remain homogeneous and translucent for 16 days within 200 nm size. Furthermore, the ultrasound-treated LRP-SeNPs exhibited higher DPPH and ABTS radical-scavenging abilities than those untreated with ultrasound. This difference may be attributed to the reason that ultrasound can reduce the SeNPs size and increase the specific surface area, which provides sufficient active sites to react with the free radicals and suppress the oxidizing reactions. The integrated results demonstrated that ultrasound played a crucial role in the dispersion, size control, stabilization and antioxidant activity of SeNPs.

Effects of vacuum chopping on physicochemical and gelation properties of myofibrillar proteins from silver carp ( Hypophthalmichthys molitrix )

Physicochemical and gelation properties of myofibrillar proteins from silver carp surimi as affected by chopping under different vacuum degrees (0, 0.01, 0.02, 0.04, 0.06 and 0.08 MPa) were investigated. With the increase of vacuum degree, size and quantity of air bubbles in surimi paste decreased, disulfide bond content of myofibrillar proteins decreased significantly (p < .05) and then slight increased (p > .05), while surface hydrophobicity of myofibrillar proteins increased gradually (p < .05). Gel mechanical properties, chemical interactions (nonspecific associations, hydrogen bond and hydrophobic interactions) and FAXL (cross-linking degree of free amino group) of heat-induced surimi gel increased significantly (p < .05) with vacuum degree. Scanning electron microscopy (SEM) observation showed that three-dimensional network of surimi gel under higher vacuum degree was more compact and orderly. Results indicated that vacuum chopping imparted physicochemical and structural changes of fish myofibrillar protein, which might contribute to the improvement in gelling properties of myofibrillar proteins.

Influence of Lactobacillus/Candida fermentation on the starch structure of rice and the related noodle features

With screening of Lactobacillus fermentum M9 and Candida santamariae Y11 from a natural fermentation broth (Jinjian) for rice noodle production, this work concerns how fermentation with M9:Y11 suspensions of different volume ratios affects the texture and sensory features of rice noodles. The M9:Y11 strains regulated rice structures and thus the physicochemical features of rice noodles. In particular, 5:5 and 8:2 v/v M9:Y11 strains endowed rice noodles with better texture and sensory performance than did Jinjian. The underlying mechanism regarding evolutions in rice noodle properties was discussed from a rice structural view. Specifically, the fermentation disrupted rice ordered structures (e.g., starch crystallites) and broke starch granules, which was preferable for the swelling and molecule leaching of rice noodle matrixes with enhanced molecule interactions. Such noodle matrixes were robust to resist imposed force, thus exhibiting increased hardness, chewiness and mouthfeel. More interestingly, the 5:5 and 8:2 v/v M9:Y11 strains less prominently altered starch granule integrity, contributing to increasing hardness, chewiness and mouthfeel of rice noodles associated with robustness of swollen granule shell within rice gel matrixes. These two ratios of M9:Y11 strains also improved the color, aroma and taste for rice noodles.

Effect of phosphates on gelling characteristics and water mobility of myofibrillar protein from grass carp (Ctenopharyngodon idellus)

Effect of phosphates on the heat-induced gel characteristics of myofibrillar protein (MP) from grass carp was investigated. Both heating and phosphates exerted significant influences. Heating induced more elastic, water-holding and less flowing gel. But phosphates had diverse effects at different temperatures. At 4 °C and 40 °C, phosphate as a dominant factor reduced the gel elasticity and resistance and increased flowability with increasing levels of phosphates. Furthermore, 280 mg/kg sodium pyrophosphate (SPP) or 440 mg/kg sodium triphosphates (STP) transformed MP from weak gel into concentrated solution. It clarified phosphates disentangled MP macromolecules and inhibited their aggregation and pre-gelation at low temperature. At 80 °C, heating accompanied with phosphates governed MP gelation. The appropriate level of phosphates (SPP superior to STP) endowed MP-phosphate gels with the lowest flowability and greatest elasticity, textural properties as well as finest microstructures. Besides, phosphates entrapped a portion of weak immobile water more tightly into smaller-sized pores of protein network.