Selenium nanoparticles coated with polysaccharide-protein complexes from abalone viscera improve growth and enhance resistance to diseases and hypoxic stress in juvenile Nile tilapia (Oreochromis niloticus).

The use of selenium nanoparticles (SeNPs) in aquaculture has been increasing gradually over the past few years. SeNPs enhance immunity, are highly effective against pathogens, and have low toxicity. In this study, SeNPs were prepared using polysaccharide-protein complexes (PSP) from abalone viscera. The acute toxicity of PSP-SeNPs to juvenile Nile tilapia and their effect on growth performance, intestinal tissue structure, antioxidation capacity, hypoxic stress, and Streptococcus agalactiae infection were investigated. The results showed that the spherical PSP-SeNPs were stable and safe, with an LC50 of 13.645 mg/L against tilapia, which was about 13-fold higher than that of sodium selenite (Na2SeO3). A basal diet supplemented with 0.1-1.5 mg/kg PSP-SeNPs improved the growth performance of tilapia juveniles to a certain extent, increased the intestinal villus length, and significantly enhanced the activities of liver antioxidant enzymes, including superoxide dismutase (SOD), glutathione peroxidase (GSH-PX), and catalase (CAT). PSP-SeNPs also enhanced the resistance of tilapia to hypoxic stress and Streptococcus agalactiae infection, with supplementation at 0.1-0.3 mg/kg exerting more obvious effects than 1.5 mg/kg. However, PSP-SeNPs at a concentration of 4.5 mg/kg and Na2SeO3 at 0.3 mg/kg negatively affected the growth, gut health, and the activity of the antioxidant enzymes of tilapia. Quadric polynomial regression analysis revealed that 0.1-1.2 mg/kg was the optimal PSP-SeNP supplementation concentration for tilapia feeds. The findings of this study lay a foundation for the application of PSP-SeNPs in aquaculture.

Preparation and growth-promoting effect of selenium nanoparticles capped by polysaccharide-protein complexes on tilapia.

BACKGROUND: Compared with traditional inorganic and organic selenium compounds, nano-selenium exhibited higher biological safety and nutritional potency. However, the biological efficacy of nano-selenium has not been comprehensively and accurately evaluated due to its dispersion instability. RESULTS: In this study, novel selenium nanoparticles (SeNPs) with high dispersion stability were successfully prepared using a polysaccharide-protein complex (PSP) as the capping agent. This was isolated from abalone viscera. The average particle size and zeta potential of polysaccharide-protein complex selenium nanoparticles (PSP-SeNPs) were 63.33 nm, and -37.1 mV, respectively. The SeNPs were firmly capped by PSP through SeO and SeN bonds, as demonstrated by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. Due to this capping, the dispersion of PSP-SeNPs remained stable for 12 months at 4 °C, as evidenced by visual inspection and multiple light scattering. Furthermore, PSP-SeNPs imparted an excellent growth-promoting effect on tilapia. The FBW, WGR, and SGR values of tilapia juveniles fed with PSP-SeNPs supplemented diets (0.5-4.5 mg/kg) were significantly higher than those of the control (P < 0.05). A weight gain rate of 4.1%-43.4% and specific growth rate of 0.15%-1.74% were obtained in tilapia during 45-day feeding. CONCLUSIONS: The use of marine viscera polysaccharides is a promising, green method for the synthesis of selenium nanoparticles. There are good opportunities for the application of the synthesized PSP-SeNPs in the life sciences. © 2020 Society of Chemical Industry.

Physicochemical Properties of Bovine Serum Albumin-Glucose and Bovine Serum Albumin-Mannose Conjugates Prepared by Pulsed Electric Fields Treatment.

The pulsed electric fields (PEF) treatment is a novel method for obtaining glycated proteins by way of a Maillard reaction between proteins and polysaccharides but its effect on the preparation of protein-monosaccharide conjugate has not been explored. This study aimed to prepare bovine serum albumin (BSA)-glucose and BSA-mannose conjugates using PEF in pH 10.0 at an intensity of 10 or 20 kV/cm, frequency of 1 kHz, pulse width of 20 µs and 73.5 pulses. The conjugates were evaluated for physicochemical properties. The results indicated that PEF not only promoted Maillard reaction between BSA and glucose or mannose but also alleviated the undesirable browning. PEF treatment favored the increased surface hydrophobicity and emulsifying activity in BSA but reduced surface hydrophobicity and foaming stability and improved foaming capacity in BSA-glucose and BSA-mannose conjugates. These findings provided useful considerations in the application of PEF treatment as a potential method to prepare BSA-monosaccharide conjugates by Maillard reaction.

Improving the water solubility of Monascus pigments under acidic conditions with gum arabic.

BACKGROUND: Monascus pigments (Mps) are natural food colorants and their stability in acidic solutions is important for application in the food industry. This study aimed to evaluate the use of gum arabic (GA) as a stabilizer for maintaining the solubility of Mps in an acidic aqueous solution exposed to a high temperature, and to analyze the molecular interactions between GA and Mps. RESULTS: Mps dispersed (0.2 g kg-1 ) in deionized water at pH 3.0-4.0 without GA formed precipitates but remained in a stable solution in the presence of GA (1 g kg-1 ). The significant improvement of Mps water solubility under acidic conditions was attributed to the formation of Mps-GA complexes, as indicated by a sharp increase in the fluorescence intensity. The results on particle size, zeta potential, and transmission electron microscopy further suggested that molecular binding of Mps to GA, electrostatic repulsion, and steric hindrance of GA were contributing factors to preventing the aggregation of Mps in acidic solutions. A mechanistic model was presented for GA-Mps interactions and complex structures. CONCLUSION: GA was proven to be an effective stabilizer of natural food colorants in acidic solutions. © 2016 Society of Chemical Industry.

Formation and Physiochemical Properties of Silver Nanoparticles with Various Exopolysaccharides of a Medicinal Fungus in Aqueous Solution.

Natural polysaccharides are the most widely used biopolymers for green synthesis of eco-friendly silver nanoparticles (AgNPs). In a previous study, a high molecular weight (MW) fraction of exopolysaccharides (EPS) produced by a medicinal fungus Cs-HK1 has been shown useful for green and facile synthesis of AgNPs in water. This study was to further evaluate the effects of molecular properties of EPS on the formation, stability and properties of AgNPs with different EPS fractions at various pH conditions. Three EPS fractions (P0.5, P2.0 and P5.0: MW high to low and protein content low to high) were reacted with silver nitrate at various pH 3.0-8.0 in water. The most favorable pH range was 5.5-8.0 for the formation and stable dispersion of AgNPs. At a given pH, the maximum amount of AgNPs was produced with P5.0, and the minimum with P0.5. The shape, size and physiochemical properties of AgNPs were strongly affected by the molecular characteristics of EPS (MW and conformation). The results may be helpful for understanding the factors and mechanisms for formation of stable AgNPs with natural polysaccharides and the interactions between AgNPs and the polysaccharide hydrocolloids in water.

Study on the metabolic effects of hexavalent chromium [Cr (VI)] on rat astrocytes using un-targeted metabolomics.

Introduction: Hexavalent chromium [Cr (VI)] has been identified as a human carcinogen and environmental pollutant capable of affecting multiple systems in the human body. However, the specific mechanisms by which Cr (VI) affects the human nervous system remain unclear. Objective: Following confirmation of Cr (VI)'s toxic effects on rat astrocytes, this study explores the metabolites and associated metabolic pathways of rat astrocytes under different doses of Cr (VI) exposure. Methods: Cell viability was assessed using CCK8 assays, intracellular reactive oxygen species (ROS) levels were measured using DCFH-DA fluorescent probes, intracellular 8-hydroxydeoxyguanosine (8-OHdG) content was determined by Elisa, mitochondrial membrane potential was observed using JC-1 probes, and key metabolites were identified through untargeted metabolomics analysis. Results: With increasing Cr (VI) doses, significant decreases in cell viability were observed in the 4, 8, and 16 mg/L dose groups (p < 0.05). Elevated levels of ROS and 8-OHdG, increased caspase-3 activity, and significant reductions in mitochondrial membrane potential were observed in the 2 and 4 mg/L dose groups (p < 0.05). Untargeted metabolomics analysis revealed Cr (VI)'s impact on key metabolites such as sphingosine and methionine. Enrichment analysis of KEGG pathways highlighted the critical roles of sphingolipid metabolism and the methionine-cysteine cycle in the effects of Cr (VI) on rat astrocytes. Conclusion: Our study underscores the potential neuro-health risks associated with environmental and occupational exposure to Cr (VI) and provides new perspectives and directions for investigating neurotoxic mechanisms.

Quantitative studies on structure-DPPH• scavenging activity relationships of food phenolic acids.

Phenolic acids are potent antioxidants, yet the quantitative structure-activity relationships of phenolic acids remain unclear. The purpose of this study was to establish 3D-QSAR models able to predict phenolic acids with high DPPH• scavenging activity and understand their structure-activity relationships. The model has been established by using a training set of compounds with cross-validated q2 = 0.638/0.855, non-cross-validated r2 = 0.984/0.986, standard error of estimate = 0.236/0.216, and F = 139.126/208.320 for the best CoMFA/CoMSIA models. The predictive ability of the models was validated with the correlation coefficient r2(pred) = 0.971/0.996 (>0.6) for each model. Additionally, the contour map results suggested that structural characteristics of phenolics acids favorable for the high DPPH• scavenging activity might include: (1) bulky and/or electron-donating substituent groups on the phenol ring; (2) electron-donating groups at the meta-position and/or hydrophobic groups at the meta-/ortho-position; (3) hydrogen-bond donor/electron-donating groups at the ortho-position. The results have been confirmed based on structural analyses of phenolic acids and their DPPH• scavenging data from eight recent publications. The findings may provide deeper insight into the antioxidant mechanisms and provide useful information for selecting phenolic acids for free radical scavenging properties.

Aaqueous exposure to silver nanoparticles synthesized by abalone viscera hydrolysates promotes the growth, immunity and gut health of zebrafish (Danio rerio).

Silver nanoparticles (AgNPs) have the potential to be used in aquaculture, but their influence on the growth and health of aquatic organisms has not been extensively investigated. In this study, the abalone viscera hydrolysates decorated AgNPs (AVH-AgNPs) were dispersed into aquaculture water at different concentrations (0, 6, 9, and 18 µg/l) to evaluate the biological effects on zebrafish (Danio rerio). The results showed that the AVH-AgNPs treatments of 6 and 9 µg/l promoted the growth and did not cause obvious damage to the gills, intestines, and livers of zebrafish. All the treatments induced catalase (CAT) and superoxide dismutase (SOD) activities and increased glutathione (GSH) content in the livers and upregulated the expression of immune related genes. The effects of 9 and 18 µg/l AVH-AgNPs treatments were more obvious. After AVH-AgNPs treatment, the abundances of some potential pathogens, such as species Plesimonas shigelloides and Pseudomonas alcaligenes and genus Flavobacterium decreased significantly. In contrast, the abundance of some beneficial bacteria that can degrade pollutants and toxins (e.g., Rhodococcus erythropolis) increased significantly. Thus, the application of low concentrations (6 ~ 18 µg/l) of AVH-AgNPs in aquaculture water is relatively safe and has a positive effect on zebrafish farming.

Toxicity and modulation of silver nanoparticles synthesized using abalone viscera hydrolysates on bacterial community in aquatic environment.

Polysaccharide decorated silver nanoparticles (AgNPs) are a new type of antibacterial agent in aquaculture, but their effects on the bacterial community structure in aquaculture water are still unknown. In this study, the primary hydrolysate from abalone (Haliotis discus hannai) viscera (AVH) was used to biosynthesize AVH-AgNPs by in situ reduction, and the crystallinity nature, size, morphology, and chemical composition were analyzed by high-resolution characterization techniques such as Ultraviolet-visible spectroscopy (UV-vis), X-rays diffraction (XRD), Transmission Electron Microscope (TEM), Dynamic light scattering (DLS), Zeta potential, inductively coupled plasma-optical emission spectrometry (ICP-OES) and Turbiscan stability index (TSI) values. Furthermore, the acute toxicity of AVH-AgNPs to zebrafish (Danio rerio) and their effects on bacterial community structure in fish culture water at low concentrations were studied. The results showed that the spherical AVH-AgNPs with an average diameter of 54.57 ± 12.96 nm had good stability, low toxicity, and good in vitro antibacterial activity. Within the experimental concentration range, all AVH-AgNPs treatments had decreased the bacterial diversity in zebrafish culture water to varying degrees. The bacteria with significantly decreased abundances were pathogenic or potential pathogenic, such as Aeromonas veronii, Flavobacterium columnare, and genera Flectobacillus and Bosea. The abundance of Haliscomenobacter sp. JS224, which might cause sludge swelling, also decreased significantly. On the other hand, the relative abundance of some bacterial taxa could remove xenobiotics (e.g., Runella defluvii and Phenylobacterium), control water eutrophication (Sediminibacterium), and reduce toxic algae proliferation (Candidatus Intestinusbacter nucleariae and Candidatus Finniella), increased significantly. Thus, the application of AVH-AgNPs in aquaculture water at low concentrations is relatively safe and has positive significance for improving the aquaculture environment. Also, AVH-AgNPs have good prospects in aquaculture.

Quantitative insight into dispersity and antibactericidal capability of silver nanoparticles noncovalently conjugated by polysaccharide-protein complexes.

Precise prediction and measurement of dispersibility of silver nanoparticles (AgNPs) under atmospheric conditions are extremely vital for their potential commercial application. In the present work, the dispersibility of AgNPs capped by polysaccharide-protein from viscera of abalone (PSP-AgNPs) was studied using the combination of ultraviolet-visible spectroscopy (UV-vis), dynamic light scattering (DLS) and multiple-light-scattering (MLS) techniques. The results showed that the combination of UV/vis, DLS and MLS not only accurately determined the dispersibility of PSP-AgNPs, but also provided detailed information about the aggregation behavior of PSP-AgNPs. Furthermore, the results revealed a high dispersibility of PSP-AgNPs in the studied environment. The system temperature, pH value and thermal treatment (pasteurization and sterilization) had no effect on the dispersion of PSP-AgNPs in the effective concentration range against the pathogenic bacteria. Besides, an excellent stable dispersion and antibacterial activity against common pathogenic vibrio was also found in the dispersed PSP-AgNPs in seawater. Overall, the study provides a suitable method for the precise measurement of the dispersibility of AgNPs in environment. The AgNPs act as a potential bactericide with good dispersion and antibacterial activity in mariculture and other fields.

Green and facile fabrication of silver nanoparticles using Konjac Glucomannan by photocatalytic strategy.

Green fabrication of highly stable silver nanoparticles (AgNPs) is vital for its development. Herein, AgNPs with enhanced stability were prepared in an environmentally friendly manner using aqueous mixture of 0.8 mM silver nitrate and 10.0 mg/mL Konjac glucomannan (KGM) through a photocatalytic strategy. AgNPs were fabricated in situ at room temperature, followed by exposure to ultraviolet light for 510 min, resulting in complete reduction of all silver ions to AgNPs-KGM. AgNPs were firmly capped at the hydroxyl and acetyl groups of KGM through the formation of AgO bonds, which promoted the stable dispersion of AgNP-KGM, as determined by TSI value of 0.29 using multiple light scattering. Furthermore, AgNPs-KGM possessed excellent antibacterial activity against Staphylococcus aureus and Escherichia coli, with MIC and MBC values of 5.11 and 10.23 µg/mL, and 10.23 and 20.46 µg/mL, respectively. The proposed protocol is facile and feasible for large-scale production, achieving the goal of green fabrication.

Fabrication of highly stable silver nanoparticles using polysaccharide-protein complexes from abalone viscera and antibacterial activity evaluation.

Silver nanoparticles (AgNPs) are eco-friendly antibacterial agents, yet their use is limited by their facile aggregation and precipitation. Therefore, the development of highly stable AgNPs is desirable. Herein, a polysaccharide-protein complex (PSP) was successfully obtained from viscera of abalone through a combination of enzymatic hydrolysis, membrane filtration, and gel permeation chromatography. Furthermore, highly stable AgNPs were successfully synthesized by using PSP as a reducing and capping agent in situ. AgNPs were firmly capped by PSP through the formation of AgO, AgN, and AgS bonds, as observed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning transmission electron microscopy. Such capping of AgNPs by PSP contributed to the stable dispersion of PSP-AgNP composites at room temperature for 12 months, as evidenced by visual inspection and multiple light scattering. Furthermore, PSP-AgNPs were found to have an excellent antibacterial activity and biocompatibility. The proposed synthesis of AgNPs with high antibacterial activity, dispersibility, and biocompatibility will be of likely benefit in the field of life science and technology.

Preparation and cellular protection against oxidation of Konjac oligosaccharides obtained by combination of γ-irradiation and enzymatic hydrolysis.

Konjac glucomannan (KGM) is an important source for preparation of Konjac oligo-glucomannan (KOG), but high molecular weight and viscosity in KGM inhibited its full degradation into KOG. In this study, KOG with a degree of polymerization between 2 and 9 was obtained by combining γ-irradiation and enzymatic hydrolysis in high yield. We investigated the protective effect of KOG against H2O2 - induced oxidative damage in vitro, using human hepatic cell line (LO2) as a cell model. Our results demonstrated that pretreating LO2 with KOG significantly increases cellular survival and antioxidant activities of GSH-Px and CAT enzymes, and reduces levels of LDH, MDA, intracellular accumulation of ROS and Ca2+ concentration within the cell. Marked protective effect against oxidative damage, in addition to obtained high yield of KOG, supports its potential use as an abundant source of antioxidant. To conclude, our study provided a theoretical perspective for future uses of KGM.

Physicochemical properties and cellular protection against oxidation of degraded Konjac glucomannan prepared by γ-irradiation.

Konjac glucomannan (KGM) is an important functional polysaccharide in food research. However, unstable dispersibility of KGM inhibits its in-depth study and wide application. In this study, a degraded KGM (100kGy-KGM), which showed excellent dispersibility and specific physicochemical properties, were obtained by γ-irradiation in a dosage of 100kGy. We investigated the protective effect of 100kGy-KGM against H2O2 induced oxidative damage in LO2 cells. Our results demonstrated that pretreatment of LO2 cells with 100kGy-KGM not only significantly increased cellular survivals and activities of GSH-Px and CAT, but also reduced levels of LDH, MDA and intracellular accumulation of ROS. The marked protective effect against oxidative damage and excellent dispersibility in 100kGy-KGM allowed its possible use as an antioxidant. Our study provided fundamental knowledge to understand the structure-functions relationships of degraded-KGM, which could result in a theoretical guidance for the future application of KGM.

Effect of molecular characteristics of Konjac glucomannan on gelling and rheological properties of Tilapia myofibrillar protein.

Konjac glucomannan (KGM) is an important gelling agent in composite gels. This study aimed to investigate the effects of KGM molecular characteristics (molecular weight, size and conformation) on gelling properties of Tilapia myofibrillar protein (TMP). In this work, TMP composite gels were prepared under neutral pH with varying KGM (native KGM, 10kGy-KGM, 20kGy-KGM, and 100kGy-KGM) of different molecular characteristics. Native KGM, 10kGy-KGM, and 20kGy-KGM exerted negative effect on gel strength or whiteness of TMP gels. Interestingly 100kGy-KGM improved gelling properties and whiteness of TMP gels. Such effects presented by varying KGM were attributed the physical filling behaviors and the interaction between KGM and TMP. These behaviors or interactions are resulted from different molecular size and conformation. Smaller molecular size (root-mean square radius, Rz 20.2nm) and approximated spherical conformation in 100kGy-KGM enhanced its interaction with TMP and maintained its compact and smooth structure, but the larger molecular size (Rz≥40.2nm) and random coil conformation in other KGMs inhibited part of actins from gelling and deteriorated the network structure. Our study provided principle knowledge to understand the structure-functions relationships of KGM-TMP composite gels. These results can be used to provide theoretical guidance for surimi gel processing.

Effects of pH and temperature on colloidal properties and molecular characteristics of Konjac glucomannan.

The hydrocolloidal characteristics of Konjac glucomannan (KGM) are important for its application as a thickening and gelling agent for liquid foods. In this study, the rheological behavior and molecular properties such as molar mass, hydrodynamic radius and chain conformation of KGM in water were determined at various pH levels (4.0-10.0) during heating from 20 to 80 °C. Acidic and neutral conditions (pH 4.0-7.0) promoted the dispersion of KGM, and alkaline condition at pH 10 favored its aggregation in water, while KGM maintained a random coil conformation in the whole pH range. Associated with the pH effects were changes in the rheological behavior during heating from 20 to 80 °C. The significant differences in the colloidal and rheological characteristics were mainly attributed to alteration of intermolecular interaction (attractive or repulsive) rather than deacetylation at various pH levels. Deacetylation occurred in both acidic and alkaline condition. The second virial value was positive in acidic and negative in alkaline condition. The results showed that hydrocolloidal characteristics of KGM in water were significantly affected by pH.

Study on preparation and separation of Konjac oligosaccharides.

To study the preparation and separation of Konjac oligosaccharides, Konjac Glucomannan was degraded by the combination of γ-irradiation and ß-mannanase, and then the degradation product was separated by ultrafiltration. To our interest, for most of Konjac oligosaccharides obtained by this method, the molecular mass was lower than 2200 Da. In addition, the 1000 Da molecular weight cut off membrane could effectively separate the Konjac oligosaccharides. In conclusion, the combination of γ-irradiation and ß-mannanase was an efficient method to obtain Konjac oligosaccharides, and the oligosaccharides of molecular mass lower than 1000 Da could be effectively separated by ultrafiltration.