Shiyong Sun

Biosorption of Strontium from Simulated Nuclear Wastewater by Scenedesmus spinosus under Culture Conditions: Adsorption and Bioaccumulation Processes and Models

Algae biosorption is an ideal wastewater treatment method when coupled with algae growth and biosorption. The adsorption and bioaccumulation of strontium from simulated nuclear wastewater by Scenedesmus spinosus were investigated in this research. One hundred mL of cultured S. spinosus cells with a dry weight of 1.0 mg in simulated nuclear wastewater were used to analyze the effects on S. spinosus cell growth as well as the adsorption and bioaccumulation characters under conditions of 25 ± 1 °C with approximately 3,000 lux illumination. The results showed that S. spinosus had a highly selective biosorption capacity for strontium, with a maximum bioremoval ratio of 76%. The adsorbed strontium ion on cell walls was approximately 90% of the total adsorbed amount; the bioaccumulation in the cytoplasm varied by approximately10%. The adsorption quantity could be described with an equilibrium isotherm. The pseudo-second-order kinetic model suggested that adsorption was the rate-limiting step of the biosorption process. A new bioaccumulation model with three parameters was proposed and could give a good fit with the experiment data. The results suggested that S. spinosus may be a potential biosorbent for the treatment of nuclear wastewater in culture conditions.

Programmed gradient descent biosorption of strontium ions by Saccaromyces cerevisiae and ashing analysis: A decrement solution for nuclide and heavy metal disposal

One of the waste disposal principles is decrement. The programmed gradient descent biosorption of strontium ions by Saccaromyces cerevisiae regarding bioremoval and ashing process for decrement were studied in present research. The results indicated that S. cerevisiae cells showed valid biosorption for strontium ions with greater than 90% bioremoval efficiency for high concentration strontium ions under batch culture conditions. The S. cerevisiae cells bioaccumulated approximately 10% of strontium ions in the cytoplasm besides adsorbing 90% strontium ions on cell wall. The programmed gradient descent biosorption presented good performance with a nearly 100% bioremoval ratio for low concentration strontium ions after 3 cycles. The ashing process resulted in a huge volume and weight reduction ratio as well as enrichment for strontium in the ash. XRD results showed that SrSO4 existed in ash. Simulated experiments proved that sulfate could adjust the precipitation of strontium ions. Finally, we proposed a technological flow process that combined the programmed gradient descent biosorption and ashing, which could yield great decrement and allow the supernatant to meet discharge standard. This technological flow process may be beneficial for nuclides and heavy metal disposal treatment in many fields.

Nano-Scale Spatial Assessment of Calcium Distribution in Coccolithophores Using Synchrotron-Based Nano-CT and STXM-NEXAFS

Calcified coccolithophores generate calcium carbonate scales around their cell surface. In light of predicted climate change and the global carbon cycle, the biomineralization ability of coccoliths has received growing interest. However, the underlying biomineralization mechanism is not yet well understood; the lack of non-invasive characterizing tools to obtain molecular level information involving biogenic processes and biomineral components remain significant challenges. In the present study, synchrotron-based Nano-computed Tomography (Nano-CT) and Scanning Transmission X-ray Microscopy-Near-edge X-ray Absorption Fine Structure Spectromicroscopy (STXM-NEXAFS) techniques were employed to identify Ca spatial distribution and investigate the compositional chemistry and distinctive features of the association between biomacromolecules and mineral components of calcite present in coccoliths. The Nano-CT results show that the coccolith scale vesicle is similar as a continuous single channel. The mature coccoliths were intracellularly distributed and immediately ejected and located at the exterior surface to form a coccoshpere. The NEXAFS spectromicroscopy results of the Ca L edge clearly demonstrate the existence of two levels of gradients spatially, indicating two distinctive forms of Ca in coccoliths: a crystalline-poor layer surrounded by a relatively crystalline-rich layer. The results show that Sr is absorbed by the coccoliths and that Sr/Ca substitution is rather homogeneous within the coccoliths. Our findings indicate that synchrotron-based STXM-NEXAFS and Nano-CT are excellent tools for the study of biominerals and provide information to clarify biomineralization mechanism.

Metabolic Influence of Psychrophilic Diatoms on Travertines at the Huanglong Natural Scenic District of China

Diatoms are a highly diversified group of algae that are widely distributed in aquatic ecosystems, and various species have different nutrient and temperature requirements for optimal growth. Here, we describe unusual psychrophilic diatoms of Cymbella in a travertine deposition environment in southwestern China in winter season. Travertine surfaces are colonized by these psychrophilic diatoms, which form biofilms of extracellular polysaccharide substances (EPS) with active metabolic activities in extremely cold conditions. The travertine in Huanglong, is a typical single crystalline calcite with anisotropic lattice distortions of unit cell parameters along axes of a and c, and this structure is suggestive of some level of metabolic mediation on mineralization. Near-edge X-ray absorption fine structure spectroscopy (NEXAFS) results further confirmed the occurrence of biogenic distortion of the crystal lattice of travertine calcite. Overall, our results imply that the metabolic influence of psychrophilic diatoms may be particularly important for promoting formation and dissolution of travertine in extremely cold environments of Huanglong. The EPS of psychrophilic diatoms will protect travertine from HCO3− etching and provide template for forming travertine when water re-flowing, in warm season.

A histone-like protein induces plasmid DNA to form liquid crystals in vitro and gene compaction in vivo.

The liquid crystalline state is a universal phenomenon involving the formation of an ordered structure via a self-assembly process that has attracted attention from numerous scientists. In this study, the dinoflagellate histone-like protein HCcp3 is shown to induce super-coiled pUC18 plasmid DNA to enter a liquid crystalline state in vitro, and the role of HCcp3 in gene condensation in vivo is also presented. The plasmid DNA (pDNA)-HCcp3 complex formed birefringent spherical particles with a semi-crystalline selected area electronic diffraction (SAED) pattern. Circular dichroism (CD) titrations of pDNA and HCcp3 were performed. Without HCcp3, pUC18 showed the characteristic B conformation. As the HCcp3 concentration increased, the 273 nm band sharply shifted to 282 nm. When the HCcp3 concentration became high, the base pair (bp)/dimer ratio fell below 42/1, and the CD spectra of the pDNA-HCcp3 complexes became similar to that of dehydrated A-form DNA. Microscopy results showed that HCcp3 compacted the super-coiled gene into a condensed state and that inclusion bodies were formed. Our results indicated that HCcp3 has significant roles in gene condensation both in vitro and in histone-less eukaryotes in vivo. The present study indicates that HCcp3 has great potential for applications in non-viral gene delivery systems, where HCcp3 may compact genetic material to form liquid crystals.

Contribution of surface functional groups and interface interaction to biosorption of strontium ions by Saccharomyces cerevisiae under culture conditions

Contribution of surface functional groups and detailed interface interaction for biosorption of strontium ions by Saccharomyces cerevisiae under culture conditions was investigated through chemical modification, in addition to spectroscopic and mesoscopic methods. The results showed that the biosorption ratio decreased approximately 10%, 60%, and 70% for ester group, carboxyl group, and amino group modified yeast cells, respectively. Fourier transform infrared spectroscopy and surface functional group potentiometric titration results revealed that –NH2, –COOH, and –OH were the major binding groups. The amino group displayed the greatest contribution to biosorption of strontium ions, followed by the carboxyl group and, finally, the ester group. Electrostatic interaction was the initial role and establishment of a coordination complex was the most common mechanism of interface interaction between strontium ions and the yeast cell surface. Mesoscopic analysis suggested that strontium ions may be first adsorbed on the cell surface and then transported into the cytoplasm. Transmembrane transport and the bioaccumulation model revealed that yeast cells may regulate the distribution of strontium ions through a transportation mechanism. A detailed interface interaction was discussed for S. cerevisiae biosorption of low concentration strontium ions under culture conditions. The results suggested that optimal biosorption for a microorganism relies upon enrichment of proteins and polysaccharides on the cell surface.

The large dendritic fissures of travertine dam exposed by Jiuzhaigou earthquake, Sichuan, southwestern China

travertine dams remain unclear because of continuously flowing water and restrictions on human–travertine contact in protected reserves. On 8 August 2017, the Sparkling Lake dam (Jiuzhaigou Scenic Area; 33°12′25.14′′N, 103°54′2.17′′E; Fig. 1a) failed following a Ms 7.0 earthquake (epicenter located at 33.20°N, 103.82°E; focal depth of approximately 20 km). A unique section of a 232-m long travertine Pools and lakes can be formed by travertine dams (Ford and Pedley 1996; Pentecost 2005), which impound clear water with dramatic ranges of blue-green colors (Florsheim et al. 2013), as seen at many World Natural Heritage sites, including Yellowstone National Park (United States), Tivoli (Italy), Pamukkale (Turkey), Plitvice (Croatia), Jiuzhaigou, and Huanglong (China). However, the fine structures of

The Lowest Boundary Age of Travertine in Dawanzhangjia Ravine, Huanglong, China

One of major challenges in paleoenvironmental reconstruction using travertine in the Huanglong area is whether one can accurately determinate the age of travertine through high-precision and high-resolution dating techniques. Previous works of C or ESR chronology, however, have shown that the variation of deposition ages of travertine was displayed inconsistent with each other even conflict. For instance, (1) The oldest travertine age (80 ka) located in the middle of this travertine succession is departure from sequential deposition; (2) Top or boundary ages in this sedimentary section, even with the same dating method (C), are three times errors, moreover, the age of the depositional sequence is not continuous. We report here the U-Th ages in lowest boundary of travertine in Dawanzhangjia Valley, Huanglong, China, to discuss the effectiveness of U-series dating for cold-water travertine and the significance of age for vicissitude of paleoenvironment.

Laboratory assessment of bioleaching of shallow eutrophic sediment by immobilized photosynthetic bacteria

Eutrophic sediment is a serious problem in ecosystem restoration, especially in shallow lake ecosystems. We present a novel bioleaching approach to treat shallow eutrophic sediment with the objective of preventing the release of nitrate, phosphate, and organic compounds from the sediment to the water column, using porous mineral-immobilized photosynthetic bacteria (PSB). Bioactivity of bacteria was maintained during the immobilization process. Immobilized PSB beads were directly deposited on the sediment surface. The deposited PSB utilized pollutants diffused from the sediment as a nutritive matrix for growth. We evaluated the effects of light condition, temperature, initial pH, amount of PSB beads, and frequency of addition of PSB beads for contaminant removal efficiency during bioleaching operations. The presented study indicated that immobilized PSB beads using porous minerals as substrates have considerable application potential in bioremediation of shallow eutrophic lakes.

Cytotoxicity of Quartz and Montmorillonite in Human Lung Epithelial Cells (A549)

In this study, A549 cell viability, extracellular activities of lactate dehydrogenase (LDH), and tumor necrosis factor (TNF)-α and interleukin (IL)-6 levels were investigated after incubation with quartz (KWC-Q4 and KWC-Q3), Nano-SiO2, and KWC-M; the micronucleus test and comet assay were carried out to evaluate the genotoxicity. The results showed there were significant differences in the cell death rate and extracellular LDH activities compared with the control group, and showed a good linear relationship in certain concentration range. All mineral particles tested can induce the increase of TNF-α after incubation with mineral powders at 200 μg/mL for merely 3 h and also induce significant increase of IL-6 for 24 h; the results indicated that inflammatory reaction can be triggered by the exposure of KWC-Q4, KWC-Q3, Nano-SiO2, and KWC-M. The results of micronucleus test showed FMN (Frequency of micronucleus number) listed as Nano-SiO2>KWC-Q3>KWC-Q4. There was no significant FMN increase of KWC-M compared with the control group, which maybe resulted from its high cell mortality at low concentration. The comet assay confirmed the genotoxicity of all tested samples, and the DNA damage: KWC-M>Nano-SiO2>KWC-Q4>KWC-Q3.