Contribution of groundwater discharge and associated contaminants input to Dongting Lake, Central China, using multiple tracers (222Rn, 18O, Cl-).

Lacustrine groundwater discharge (LGD) can play an important role in water and contaminant mass balance of lakes. Dongting Lake is the second largest fresh lake in China which is connected to Yangtze River and has quite prominent ecological status and function within Yangtze River basin. However, the effect of groundwater discharge on the balance of water and contaminant in Dongting Lake has long been overlooked. This study estimated the groundwater discharge and associated contaminants input into Dongting Lake during the dry season using multiple tracers (222Rn, 18O, Cl-). After sensitivity analysis of different models, it is found that the result of 222Rn mass balance model is the most reliable. Based on the 222Rn mass balance model, the groundwater discharge rate is estimated to be 73.94 mm/d and the contribution of LGD to water balance is 10.94%. As the main nutrient components, NH3-N, P and Si from groundwater input account for 23.65%, 5.12% and 30.15%  % of the total input, respectively. As the main heavy metal components, Fe, Mn and As from groundwater input all account for more than 50% of the total input. Although the LGD rate is relatively small, the contaminant input from LGD is significant enough, which may be a potential threat to the ecological stability of Dongting Lake. In this study, the mass balance models of multiple tracers were integrated to understand the role of groundwater in maintaining the water balance and pollution status of Dongting Lake, which has certain reference significance for the LGD study in plain lakes or reservoirs with complex water systems in humid regions.

Technology for Blending Recombined Flour: Substitution of Extruded Rice Flour, Quantity of Addition, and Impact on Dough.

In a previous study, rice bread was prepared using a combination of rice-wheat mixed flour. To investigate the impact of the partial adoption of extruded rice flour (ERF) on mixed flour (MF) and mixed dough (MD), the effects of adding ERF on the pasting, mixing characteristics, texture, and water retention of the MF and MD were examined by a rapid visco analyzer (RVA), Mixolab, texture profile analysis (TPA), and a low-field nuclear magnetic resonance analyzer (LF-NMR). The PV, TV, BD, FV, and SV of the MF declined as the incorporated amount of ERF increased. There was no significant difference in the PT at the 5-15% addition level (p < 0.05), but it showed an increasing trend at the 20-30% level (p < 0.05). The incorporation of ERF led to a significant increase in the water absorption (WA) of the MD, while the DT, ST, C2, C3, C4, and C5 exhibited a declining trend. The texture analysis revealed a significant decrease in the dough hardness with the addition of ERF, with a 55% reduction in the hardness of the 30% improved mixed dough (IMD), and the cohesiveness increased significantly (p < 0.05). The IMD was mainly composed of weakly bound water. The content of weakly bound water increased with the ERF amount.

Methanobactin-mediated one-step synthesis of gold nanoparticles.

Preparation of gold nanoparticles with a narrow size distribution has enormous importance in nanotechnology. Methanobactin (Mb) is a copper-binding small peptide that appears to function as an agent for copper sequestration and uptake in methanotrophs. Mb can also bind and catalytically reduce Au (III) to Au (0). In this study, we demonstrate a facile Mb-mediated one-step synthetic route to prepare monodispersed gold nanoparticles. Continuous reduction of Au (III) by Mb can be achieved by using hydroquinone as the reducing agent. The gold nanoparticles have been characterized by UV-visible spectroscopy. The formation and the surface plasmon resonance properties of the gold nanoparticles are highly dependent on the ratio of Au (III) to Mb in solution. X-ray photoelectron spectroscopy (XPS), fluorescence spectra and Fourier transform-infrared spectroscopy (FT-IR) spectra suggest that Mb molecules catalytically reduce Au (III) to Au (0) with the concomitant production of gold nanoparticles, and then, Mb statically adsorbed onto the surface of gold nanoparticles to form an Mb-gold nanoparticles assembly. This avoids secondary nucleation. The formed gold nanoparticles have been demonstrated to be monodispersed and uniform by transmission electron microscopy (TEM) images. Analysis of these particles shows an average size of 14.9 nm with a standard deviation of 1.1 nm. The gold nanoparticles are extremely stable and can resist aggregation, even after several months.

Effects of lactic acid bacteria fermentation on the physicochemical and structural characteristics of starch in blends of glutinous and japonica rice.

In this study, the effects of lactic acid bacteria (LAB) fermentation on the physicochemical and structural characteristics of mixed starches in blends of glutinous and japonica rice were investigated. Five starter cultures improved in varying degrees the hydration ability, transparency, and freeze-thaw stability of the mixed starches. Mixed starch I, prepared by fermentation of Lactobacillus acidophilus HSP001, exhibited optimal water-holding capacity, solubility, and swelling power. In comparison, mixed starches V and III involved fermentation of L. acidophilus HSP001 and Latilactobacillus sakei HSP002, using ratios of 2:1 and 1:1 to achieve higher transparency and freeze-thaw stability, respectively. The LAB-fermented, mixed starches exhibited excellent pasting properties due to their high peak viscosities and low setback values. Moreover, the viscoelasticity of mixed starches III-V, prepared by compound fermentation of L. acidophilus HSP001 and L. sakei HSP002 in ratios of 1:1, 1:2, and 2:1, respectively, proved superior to their single strain fermentation counterparts. Meanwhile, LAB fermentation resulted in reduced gelatinization enthalpy, relative crystallinity, and short-range ordered degree. Thus, the effects of five LAB starter cultures on mixed starches were inconsistent, but these results provide a theoretical basis for the application of mixed starches. PRACTICAL APPLICATION: Lactic acid bacteria was used to ferment blends of glutinous and japonica rice. Fermented mixed starch had better hydration, transparency, and freeze-thaw stability. Fermented mixed starch exhibited nice pasting properties and viscoelasticity. LAB fermentation corroded starch granules, leading to the decrease of ΔH. Relative crystallinity and short-range order of fermented mixed starch decreased.

Methanobactin-mediated synthesis of bimetallic Au-Pd/Al2O3 toward an efficient catalyst for glucose oxidation.

A green bioreductive approach with methanobactin was adopted to fabricate bimetallic Au-Pd/Al2O3 catalysts for solvent-free oxidation of glucose to gluconic acid with H2O2 at atmospheric pressure. The catalyst was characterised by diffuse reflectance UV-vis spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction techniques to understand synergistic interactions between Au and Pd. Effects of Au to Pd molar ratio on the catalytic activity of Au-Pd/Al2O3 were investigated. The Au-Pd/Al2O3 catalyst with Au/Pd molar ratio of 0.8:0.2 exhibited excellent catalytic performance. With the catalyst, the oxidation activities of glucose to gluconic acid 2856 mmol min-1 g-1 and selectivity 99.6% were attained at 323 K with H2O2. The results indicated the activity and selectivity was affected by the ratio of Au/Pd on the Al2O3. The formation of Au0.8Pd0.2/Al2O3 was favourable for the catalytic reaction.

Colorimetric detection of melamine based on methanobactin-mediated synthesis of gold nanoparticles.

A simple and rapid field-portable colorimetric method for the detection of melamine in liquid milk was reported. Methanobactin (Mb) could reduce Au (III) to Au (0) and mediate the synthesis of gold nanoparticles (Au-NPs). Upon the addition of melamine, melamine interacted with oxazolone ring of Mb, which interrupted the formation of Au-NPs. Melamine could also stimulate the aggregation of formed Au-NPs. In this paper, these characteristics have been used to detect melamine in liquid milk by naked eyes observation with a detection limit of 5.56 × 10(-6)M (0.7 mg/kg). Further, the plasmon absorbance of the formed Au-NPs allowed the quantitative detection of melamine by UV-vis spectrometer. A linear correlation was existed between the absorbance and the melamine concentration ranging from 3.90 × 10(-7)M to 3.97 × 10(-6)M with a correlation coefficient of 0.9685. The detection limit (3σ) obtained by UV-vis spectrum was as low as 2.38 × 10(-7)M (i.e., 0.03 mg/kg).