Pullulan suppresses the denaturation of myofibrillar protein of grass carp (Ctenopharyngodon idella) during frozen storage.

This study aims to investigate the effect of pullulan on the denaturation of the myofibrillar protein of grass carp (Ctenopharyngodon idella) during frozen storage at -18°C for 30days. Pullulan or commercial cryoprotectant (1g dry weight) were added to 100g of the myofibrillar protein of grass carp (C. idella), respectively, which was frozenly stored at -18°C for 30days, and the changes in the state of unfrozen of water, solubility, Ca2+-adenylpyrophosphatase (ATPase) activity, and sulfhydryl content of myofibrils were monitored during frozen storage. Pullulan addition increased unfrozen water and sulfhydryl contents in the myofibrillar protein and solubility and ATPase activity of the myofibrillar protein compared with those of the control during frozen storage at -18°C. Moreover, the cryoprotective efficiency of pullulan on the myofibrillar protein of grass carp (C. idella) was higher than that of commercial cryoprotectant.

Stimulating effects of polysaccharide from Angelica sinensis on the nonspecific immunity of white shrimps (Litopenaeus vannamei).

Angelica sinensis polysaccharide (ASP) was prepared by hot water extraction. Then, high-performance liquid chromatography and ion chromatography analyses were conducted, and the results indicated that ASP is a heteropolysaccharide, has a molecular mass of 82,000 Da and consists of arabinose, galactose and glucose (molar ratio of 6:1:1). The effects of ASP on the nonspecific immunity of white shrimps (Litopenaeus vannamei) were investigated by feeding them with ASP-containing diets (0.5, 1 and 1.5 g/kg) during a 12-week breeding experiment. Oral ASP administration significantly improved the survival rate, phenoloxidase activity, superoxide dismutase activity, glutathione peroxidase level, disease resistance against V. alginolyticus, total haemocyte count and number of hyaline cells, semigranular cells and granular cells (p < .05). ASP exhibits immunostimulatory effects on Pacific white shrimps (L. vannamei) and may thus be used as a diet supplement for them.

Physical process-aided fabrication of periodic Au-M (M = Ag, Cu, Ag-Cu) alloyed nanoparticle arrays with tunable localized surface plasmon resonance and diffraction peaks.

Periodic alloyed (Au-Ag, Au-Cu, Au-Ag-Cu) nanoparticle (NP) arrays with uniform size, controllable composition and center-to-center spacing were fabricated by a novel and facile strategy based on physical vapor deposition on a monolayer colloidal crystal template and further heat treatment. The composition and center-to-center spacing were manipulated by adjusting the sputtering target in the deposition process and the size of colloidal spheres of the template, respectively. The shadow effect and a dewetting model were employed to analyze the whole process of evolution from a metallic thin film to spherical nanoparticles with uniform size. The localized surface plasmon resonance (LSPR) and diffraction peaks of these alloyed arrays were systematically measured. The dielectric constant has an important influence on LSPR peaks and diffraction peaks. Both the LSPR and diffraction peaks of Au-Ag alloyed NPs arrays exhibit a blue shift due to their lower dielectric constant than that of pure Au NPs. However, compared with Au, Cu possesses a higher dielectric constant, leading to a red shift of the LSPR and diffraction peaks of Au-Cu alloyed NPs arrays. With the increase of NP size, the diffraction peaks of both binary alloyed NPs exhibit a slight red shift. Moreover, the LSPR absorption peaks were more sensitive to the composition of the NPs than the diffraction peaks. This work would open up a novel strategy in the production of alloyed NP arrays with tunable LSPR peaks and diffraction peaks, which would be very helpful to improve their practical applications in various fields.

Pullulan-based coatings for preservation of razor clam Sinonovacula constricta.

Glutathione has antioxidant activity, and citric acid exhibits acidity. Potassium sorbate displays antibacterial activity. Effects of pullulan-based coatings with 0.05% glutathione, 0.5% citric acid and 0.2% potassium sorbate on the preservation of razor clam Sinonovacula constricta meats (SCMs) during refrigerated storage (∼2°C) were investigated. The glutathione-, citric acid- and potassium sorbate-incorporated pullulan-based coatings inhibited bacterial growth. Moreover, results showed reduced increase in pH, decreased total volatile basic nitrogen and enhanced overall acceptability score of SCMs during refrigerated storage (∼2°C). These results indicated that treatment with pullulan-based coatings with glutathione, citric acid and potassium sorbate could prolong the shelf life of SCM for up to 10 days.

Preparation and antibacterial activity of the oligosaccharides derived from Rhizoma Phragmites.

In this study, we prepared Rhizoma Phragmites derived oligosaccharides (ROs) by hydrolysis with hydrogen peroxide (H2O2). The ROs yield was affected by reaction time, temperature, and H2O2 concentration. Too long reaction time and too high temperature decreased the ROs yield. Maximum ROs yield (11.26%) was obtained at reaction time 4h, temperature 75 °C, and H2O2 concentration 3.5% (v/v). The oligosaccharides sample contained 93.16% sugar, of which the average degree was approximately 11, was water-soluble, and showed white. The ROs had the highest antibacterial activity against Staphylococcus aureus, followed by Bacillus subtilis and Escherichia coli at the concentration of 100 µg/mL.

Cellulase-assisted extraction and antioxidant activity of polysaccharides from Rhizoma imperata.

In this study, the cellulase-assisted extraction and antioxidant activity of the polysaccharides from Rhizoma imperata were investigated. To improve the yield of R. Imperata polysaccharides (RPs), the extraction conditions were optimized as follows: time, 69.48 min; temperature, 45.36°C; pH, 4.58; cellulase amount, 1,200 U/g. Under these optimum conditions, the yield of RPs reached 0.67% (w/w), and was higher than that of the traditionally aqueous extraction method. The sugar content in the RPs product reached up to 93.25% (w/w). The RPs product has high antioxidant activity including hydroxyl radical scavenging activity and 2,2-diphenyl-ß-picrylhydrazyl radical scavenging activity at the concentration of 100mg/mL.

The polysaccharides from porphyra yezoensis suppress the denaturation of bighead carp myofibrillar protein.

In this study, investigated was the effect of the porphyra yezoensis polysaccharides (PPs) on the denaturation of bighead carp (Aristichthys nobilis) myofibrillar protein (Mf) during frozen storage at -18°C for 90d. The PPs (2.5%, 5%, and 7.5%, respectively) was added to 100g of Mf. The changes in the Ca-adenylpyrophosphatase (ATPase) activity and unfrozen water content in Mf were examined to evaluate he denaturation of Mf during frozen storage. Ca-ATPase activity decreased gradually during frozen storage at -18°C upon addition of PPs. By contrast, Ca-ATPase activity in the control group dropped drastically during the first 45d of storage and then further decreased gradually for up to 90d of storage, indicating a biphasic denaturation pattern. PPs addition significantly increased sulfhydryl contents in the Mf of the treatment groups compared with that of the control group (p<0.05) during frozen storage at -18°C.

Preparation and antioxidant activity of Lycium barbarum oligosaccharides.

In this study, the Lycium barbarum oligosaccharides (LBO) were prepared by hydrolysis using hydrogen peroxide (H2O2). The yield of the LBO was monitored during the hydrolysis process. The hydrolysis conditions were optimized as follows: time, 4h; temperature, 70 °C; and H2O2 concentration, 2.5% (v/v). The hydrolysates were filtered, concentrated to ∼20% (w/v), precipitated with 6 volumes of absolute ethanol, freeze-dried, and ground to yield a water soluble and white powder. The sugar content of the product was 95.8%, and the yield was 21.05% (w/w), respectively. The LBO show higher hydroxyl radical scavenging activity (86.46%) than Vc (40.96) at the concentration of 100 µg/mL.

Effect of nitrogen source on curdlan production by Alcaligenes faecalis ATCC 31749.

This study aims to investigate the effect of nitrogen source on curdlan production by Alcaligenes faecalis ATCC 31749. Curdlan production fell when excess nitrogen source was present, while biomass accumulation increased as the level of nitrogen source raised. Curdlan production and biomass accumulation were greater with urea compared with those with other nitrogen sources. The highest production of curdlan and biomass accumulation by A. faecalis ATCC 31749 was 28.16 g L(-1) and 9.58 g L(-1), respectively, with urea, whereas those with NH(4)Cl were 15.17 g L(-1) and 6.25 g L(-1), respectively. The optimum fermentation time for curdlan production was also affected by the nitrogen source in the medium.