Lixiao Ni

Isolation and identification of an anti-algal compound from Artemisia annua and mechanisms of inhibitory effect on algae

The goals of this work were to isolate and identify an anti-algal compound from extracts of Artemisia annua and study its mode of action on Microcystis aeruginosa. The anti-algal compound was isolated from the extracts using column chromatography and activity-guided fractionation methods. Artemisinin with strong anti-algal activity was identified by gas chromatography-mass spectrometry and (1)H Nuclear Magnetic Resonance. The EC(50) of artemisinin on M. aeruginosa was 3.2mg L(-1). Artemisinin decreased the soluble protein content and increased the superoxide dismutase activity and ascorbic acid content of M. aeruginosa, but exerted no effect on soluble sugar content. The results suggested the mode of action of artemisinin on algae may primarily be the increasing level of reactive oxygen species in algae cells. The results of our research could aid in the development of new anti-algal substances and lead to further study of mechanisms of inhibitory effect on algae.

Effect of linoleic acid sustained-release microspheres on Microcystis aeruginosa antioxidant enzymes activity and microcystins production and release.

The objective of this work was to identify the optimal dose range for good anti-algal effect of linoleic acid (LA) sustained-release microspheres and investigate their impact on the antioxidant enzymes (super oxide dismutase, Catalase and Peroxidase) activity changes of Microcystis aeruginosa, as well as the production and release of microcystins (MCs). Based on measured changes in algal cell density and inhibitory ratio (IR), the optimal dose of LA microspheres was 0.3 g L(-1) with over 90% of IR in this study. The Chlorophyll a content and antioxidant enzymes activity in the LA microspheres group decreased markedly until beyond the minimal detection limit after 16 d and 9 d, respectively. In addition, LA microspheres demonstrated no significant impact on the extracellular release of MCs during the culturing period. The amount of intracellular microcystin-LR (MC-LR) per 10(6) algal cells in LA microspheres group was highest among all groups during the whole experimental process. Under the sustained stress of LA released from LA microspheres, the LA microspheres could decrease the production and release of algal toxins. There was no increase in the total amount of MC-LR in the algal cell culture medium. These indicated that LA sustained-release microspheres represent a high degree of ecological safety and their practical applications for the treatment of water undergoing algal blooms need further study.

Effects of Artemisinin on Photosystem II Performance of Microcystis aeruginosa by In Vivo Chlorophyll Fluorescence

Effects of artemisinin (derived from Artemisia annua) on the photosynthetic activity of Microcystis aeruginosa was investigated by using chlorophyll a (Chl a) fluorescence transient O-J-I–P and JIP-test after exposure to elevated artemisinin concentration. High artemisinin concentration resulted in a significant suppression in photosynthesis and respiration. Results showed that the OJIP curves flattened and the maximal fluorescence yield reached at the J step under artemisinin stress. The decreased values of the energy needed for the RCs’ closure (Sm) and the number of oxidation and reduction (N) suggested that the reduction times of primary bound plastoquinone (QA) was also decreased. The absorption flux (ABS/RC) per photosystem II (PSII) reaction center and the electron transport flux (ET0/RC) decreased with increasing artemisinin concentration. Excess artemisinin had little effect on the trapping flux (TR0/RC). The results showed that the decrease of photosynthesis in exposure to excess artemisinin may be a result of the inactivation of PSII reaction centers and the inhibition of electron transport in the acceptor side.

Characterization of unsaturated fatty acid sustained-release microspheres for long-term algal inhibition.

The unsaturated fatty acid (linoleic acid) sustained-release microspheres were prepared with linoleic acid (LA) using alginate-chitosan microcapsule technology. These LA sustained-release microspheres had a high encapsulation efficiency (up to 62%) tested by high performance liquid chromatography with a photo diode array. The dry microspheres were characterized by a scanning electron microscope, X-ray diffraction measurement, dynamic thermogravimetric analysis and Fourier transform infrared spectral analysis. The results of characterization showed that the microspheres had good thermal stability (decomposition temperature of 236°C), stable and temperature independent release properties (release time of more than 40 d). Compared to direct dosing of LA, LA sustained-released microspheres could inhibit Microcystis aeruginosa growth to the non-growth state. The results of this study suggested that the LA sustained-release microspheres may be a potential candidate for algal inhibition.

Preparation and characterization of anti-algal sustained-release granules and their inhibitory effects on algae

The objectives of this work were to prepare and characterize an anti-algal sustained-release granule, then study its mode of action on Microcystis aeruginosa. The anti-algal sustained-release granule was prepared with artemisinin using alginate-chitosan microcapsule technology and characterized by a high performance liquid chromatography with an evaporative light-scattering detector, Fourier transform infrared spectral analysis, and a scanning electron microscope. The optimum preparation (in %, w/v) using the orthogonal method was: 2.5 sodium alginate; 0.25 chloride; 0.6 artemisinin; 2 calcium chloride; and 1.5 mL of the cross-linking agent, glutaraldehyde. These artemisinin sustained-release granules had a high encapsulation efficiency (up to 68%) and good release properties (release time of more than 40 d). Artemisinin sustained-release granules released cumulatively in a solution containing M. aeruginosa, and the stress on algae increased gradually within 30 d. Artemisinin sustained-release granules decreased the content of the soluble protein, Chlorophyll a in 30 d, increased the superoxide dismutase activity of M. aeruginosa, but exerted no effect on the soluble sugar content. Compared to direct dosing of artemisinin, algae can be inhibited longer and more effectively by the artemisinin sustained-release granules. The results of our research can aid in the development of new anti-algal sustained-release granules and lead to further study of their application in the field.

The characterization of dissolved organic matter extracted from different sources and their influence on cadmium uptake by Microcystis aeruginosa

The present study examines the uptake of the heavy metal cadmium (Cd) by Microcystis aeruginosa in the presence of dissolved organic matter (DOM) from different origins. The DOM used in the present study were extracted from soil, sediment taken from Meiliang Bay at Taihu Lake, and from M. aeruginosa cultured in the laboratory. The 3 different DOM samples were characterized using ultraviolet-visible absorption spectroscopy and Fourier transform infrared spectroscopy. The excitation-emission matrix (EEM) fluorescence spectroscopy was used to characterize the interactions of DOM with Cd2+ . The results showed that all types of DOM extracted from the 3 sources in the present study exhibited aliphatic and aromatic characteristics and contained hydroxyls, carbonyls, phenols, carboxyls, carbohydrates, amines, and ethers. Humic acids and fulvic acids proved to be the major components of DOM. The sediment DOM had the highest degrees of aromatization and humification among the samples. The results also showed that sediment and soil DOM samples had lower molecular weights than M. aeruginosa DOM. The DOM could react with Cd2+ by complexing to alter Cd speciation. When exposed to Cd, EEM fluorescence intensities of all 3 DOM types had a significant decrease, and the intracellular Cd content improved with increasing Cd concentrations. The addition of DOM greatly enhanced Cd uptake by M. aeruginosa compared with the control group. Environ Toxicol Chem 2017;36:1856-1863.

Correlation Among Soil Enzyme Activities, Root Enzyme Activities, and Contaminant Removal in Two-Stage In Situ Constructed Wetlands Purifying Domestic Wastewater.

Two-stage in situ wetlands (two vertical flow constructed wetlands in parallel and a horizontal flow constructed wetland) were constructed for studying domestic wastewater purification and the correlations between contaminant removal and plant and soil enzyme activities. Results indicated the removal efficiency of NH4+ and NO3− were significantly correlated with both urease and protease activity, and the removal of total phosphorus was significantly correlated with phosphatase activity. Chemical oxygen demand removal was not correlated with enzyme activity in constructed wetlands. Plant root enzyme (urease, phosphatase, protease and cellulose) activity correlation was apparent with all contaminant removal in the two vertical flow constructed wetlands. However, the correlation between the plant root enzyme activity and contaminant removal was poor in horizontal flow constructed wetlands. Results indicated that plant roots clearly played a role in the removal of contaminants.

Rapid Removal of Tetracycline (TC) by Ozonation after Extraction TC from Water into Acetic Acid Solution Using Granular Activated Carbon

This study quantifies the rapid removal of tetracycline (TC) in acetic acid solution by ozonation after extraction from water into acetic acid solution using granular activated carbon (GAC). Systematic laboratory experiments show that GAC can be used as an adsorbent to transfer TC from water to acetic acid. Ozone gas has a high degree of stability and solubility in acetic acid, and therefore apparently enhances the removal rate of TC. TC removal efficiency is better in 10% acetic acid solution than that in water, 15% and 20% acetic acid solution. Removal rate of TC in the acetic acid solution decreases as the initial molar ratio of TC and O3 increases. Inhibition effect of tertiary butyl alcohol (TBA) on TC removal is smaller in acetic acid than that in water. metal-TC complex was produced in the presence of Fe3+ and Co3+, which inhibited the degradation of TC by ozone in acetic acid. Removal of TC by ozone in the acetic acid solution might be affected by multiple factors, which should be considered in practical applications.

Rapid Removal of Nitrobenzene in a Three-Phase Ozone Loaded System with Gas–Liquid–Liquid

This study explores the removal rate of nitrobenzene (NB) using a new gas–liquid–liquid (G–L–L) three-phase ozone-loaded system consisting of a gaseous ozone, an aqueous solvent phase, and a fluorinated solvent phase (perfluorodecalin, or FDC). The removal rate of NB was quantified in relation to six factors including (1) initial pH, (2) initial NB dosage, (3) gaseous ozone dosage, (4) free radical scavenger, (5) FDC pre-aerated gaseous ozone, and (6) reuse of FDC. NB removal rate is positively affected by the first three of these factors. Compared with the conventional gas–liquid (water) (G–L) two-phase ozonation system, the free radical scavenger (tertiary butyl alcohol) has much less influence on the removal rate of NB in the G–L–L system. The FDC-loaded ozone acts as an ozone reservoir and serves as the main reactive phase in the G–L–L three-phase system. The reuse of FDC has little influence on the removal rate of NB. These experimental results suggest that the oxidation efficiency of ozonation in the G–L–L three-phase system is better than that in the conventional G–L two-phase system.

Research on adsorption of cationic dyes by waste brewer's yeast

The potential of waste brewers yeast(WBY) used as bio-adsorbent to adsorb BasicGreen(BG) was investigated in this paper. Adsorption of BG was pH-dependent and the optimum pH for cation dye is 5.0 . Kinetic process of Basic Green adsorbed by waste brewerys yeast can well described by pseudo-second-order models. With the increase of initial dye concentration, the adsorption quantity increased and the adsorption percentages of the dyes decreased . The higher the initial concentration was, the longer the time required to reach adsorption equilibrium was. The higher the temperature was, the greater the adsorption on dye by WBY was and the adsorption is also easier to carry out. To the dyes, the isothermal data of adsorption followed both the Langmuir and Freundlich models, but much butter to the Freundlich models. Amino, amide, carboxyl, phosphate groups are responsible for the dye adsorbed by waste brewerys yeast. The results in this study indicated that WBY was a good cationic dye sorbent and a low cost biomaterial for dye wastewater treatment. It is feasible to use WBY to adsorp cationic dye wastewater.