Danfeng Wang

Production of chitin from shrimp shell powders using Serratia marcescens B742 and Lactobacillus plantarum ATCC 8014 successive two-step fermentation.

Shrimp shell powders (SSPs) were fermented by successive two-step fermentation of Serratia marcescens B742 and Lactobacillus plantarum ATCC 8014 to extract chitin. Taguchi experimental design with orthogonal array was employed to investigate the most contributing factors on each of the one-step fermentation first. The identified optimal fermentation conditions for extracting chitin from SSPs using S. marcescens B742 were 2% SSP, 2h of sonication time, 10% incubation level, and 4d of culture time, while that of using L. plantarum ATCC 8014 fermentation was 2% SSP, 15% glucose, 10% incubation level, and 2d of culture time. Successive two-step fermentation using identified optimal fermentation conditions resulted in chitin yield of 18.9% with the final deproteinization (DP) and demineralization (DM) rate of 94.5% and 93.0%, respectively. The obtained chitin was compared with the commercial chitin from SSP using scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FT-IR) and X-ray diffraction (XRD). Results showed that the chitin prepared by the successive two-step fermentation exhibited similar physicochemical and structural properties to those of the commercial one, while significantly less use of chemical reagents.

Optimization of the fermentation conditions of Rhizopus japonicus M193 for the production of chitin deacetylase and chitosan

To improve the production of chitin deacetylase (CDA) for the bioconversion of chitin to chitosan with desirable functionality, the effect of the nutritional requirement on the CDA production from Rhizopus japonicus M193 fermentation was investigated under submerged conditions. Nutritional elements including glucose (g/L), inoculum level (%), and MgSO4·7H2O (g/L), as well as culture time (d) were identified as the most critical factors for the CDA production based on the results from Plackett-Burman design (PBD). Taguchi design with orthogonal array was further employed to optimize R. japonicus M193 fermentation conditions based on the results from PBD, in which 2.5% chitin, 5 g/L glucose, 5% inoculum level, 0.6g/L MgSO4·7H2O, and 5d culture time were identified as the optimal fermentation conditions. Under this condition, the maximum CDA production, DDA and MM of produced chitosan were 547.38 ± 12.06 U/L, 78.85 ± 1.68%, and 125.63 ± 3.74 kDa, respectively. Obtained chitosan displayed similar physicochemical and structural properties to those of commercial chitosan extracted using chemical method based on the results from Fourier transform infrared spectrometer (FT-IR), thermogravimetric analysis (TGA)-differential scanning calorimetry (DSC), and nuclear magnetic resonance (NMR) assays, while the use of chemical reagents was significantly reduced.

Comparison of microbiological loads and physicochemical properties of raw milk treated with single-/multiple-cycle high hydrostatic pressure and ultraviolet-C light

The effects of ultraviolet-C radiation (UV-C, 11.8 W/m2), single-cycle and multiple-cycle high hydrostatic pressure (HHP at 200, 400 or 600 MPa) on microbial load and physicochemical quality of raw milk were evaluated. Reductions of aerobic plate count (APC) and coliform count (CC) by HHP were more than 99.9% and 98.7%, respectively. Inactivation efficiency of microorganisms increased with pressure level. At the same pressure level, two-cycle treatments caused lower APC, but did not show CC differences compared with single-cycle treatments. Reductions of APC and CC by UV-C were somewhere between 200 MPa and 400/600 MPa. Both HHP and UV-C significantly decreased lightness and increased pH, but did not change soluble solids content and thiobarbituric acid-reactive substances’ values. Two 2.5 min cycles of HHP at 600 MPa caused minimum APC and CC, and maximum conductivity. Compared with HHP, UV-C markedly increased protein oxidation and reduced darkening.

VPPIPP and IPPVPP: two hexapeptides innovated to exert antihypertensive activity.

In this study, two hexapeptides of IPPVPP and VPPIPP were innovated by using two commercial antihypertensive peptides IPP and VPP as two domains cis-linked and trans-linked, respectively. The IPPVPP and VPPIPP were chemically synthesized and evaluated for the antihypertensive activity in vitro/vivo. The in vitro ACE-inhibitory study showed that VPPIPP (34.71±4.38%) has a significantly stronger activity than that of IPPVPP (13.17±0.25%) at a treatment concentration of 10 µmol/L, but it was weaker than the commercial IPP (56.97±2.40%) (P<0.05). However, VPPIPP, IPPVPP, and IPP lowered the systolic blood pressure by 21±0.9%, 17.4±1.3% and 17.5±0.9%, respectively, in rats at 1.5 mg/kg body weight dosage. The result was consistent with the mRNA level of sarcoplasmic reticulum Ca2+, Mg2+ -ATPase Gene (SERCA 2a) in rat hearts. Additionally, VPPIPP and IPPVPP showed no negative impact on blood glycometabolism. The results suggested that the two hexapeptides could be potent bioactive peptides in functional foods for people with high blood pressure.

Degradation kinetics and antioxidant capacity of anthocyanins in air-impingement jet dried purple potato slices

We investigated the types, degradation kinetics, and antioxidant capacities of anthocyanins in purple potato slices subjected to air-impingement jet drying (AIJD) at different drying temperatures (50, 65, and 80°C). Petunidin-3-p-coumaroylrutinoside-5-glucoside was the predominant anthocyanin in AIJD-treated purple potato and was positively correlated with antioxidant capacity. Anthocyanin concentration decreased with drying time, and anthocyanin degradation followed first-order reaction kinetics. At high drying temperatures, anthocyanin degradation had higher degradation rates and shorter half-life than at low drying temperatures. Thermodynamic results revealed that the degradation of anthocyanins is a non-spontaneous, endothermic reaction and that the transition state has lower structural freedom than the reactant. AIJD at 65°C contributed to the highest anthocyanin content and antioxidant capacity.

Structural and oxidative modifications, and antioxidant activity of β-lactoglobulin treated by ultraviolet light-C and ultrasound

ABSTRACT β-Lactoglobulin (β-Lg) was treated with ultraviolet light-C (UV-C) at 11.8 W m–2 or ultrasound at 900 W for 15 or 30 min. All treatments increased the β-structure, free sulfhydryl groups (FSH), dityrosine, and ABTS radical scavenging activity, but decreased the α-helicity, random coils, disulfide bonds (S–S), and intrinsic fluorescence intensity. UV-C treatment produced higher surface hydrophobicity (Ho), carbonyl, dityrosine, and antioxidant activity, and lower fluorescence intensity, total sulfhydryl group (TSH), and S–S compared with ultrasound treatment. UV-C treatment for 30 min gave the maximum Ho, carbonyl, dityrosine, and antioxidant activity, but the minimum TSH and S–S contents from β-Lg. Ultrasound treatment for 15 min produced the maximum β-sheet, TSH, and S–S contents, while treatment for 30 min gave the minimum carbonyl, dityrosine, and antioxidant activity. Data obtained in this study suggest that ultrasound and UV-C treatments demonstrated the potential for improving antioxidant activity in β-Lg, especially UV-C treatment.

Impact of UV-C Radiation on Antioxidant Activity, Malondialdehyde and Quality of Pleurotus Eryngii

The aim of this study was to investigate the effect of different doses of ultraviolet C (UV-C) radiation (0[control], 2, 3, 4 kJ/m 2 ) on antioxidant contents, antioxidant capacity and quality of postharvest Pleurotus eryngii during storage at 2°C for 35 days . Samples treated with UV-C radiation maintained the color and the total soluble solids better than the control. UV-C radiation decreased the accumulation of malondialdehyde but increased total phenolic contents compared with the control. Moreover, UV-C radiation improved the antioxidant capacity and reducing power of the mushroom compared with control. However, the effects of different UV-C radiation treatments on respiration were not statistically ( P >0.05) significant. In summary, all results suggested that UV-C radiation had the potential to extend the shelf life and improve the total antioxidant capacity of Pleurotus eryngii .