有机锡对斜生栅藻(Scenedesmus obliquu)的毒性影响试验研究

有机锡对海洋环境有着很大的破坏作用,为此以一甲基氯化锡(CH3SnC l3)和二甲基氯化锡((CH3)2SnC l2)为代表,研究了不同浓度有机锡对斜生栅藻(Scenedesmus obliquus)的毒性影响,并且对两种有机锡的毒性进行了对比试验。结果表明,一甲基氯化锡和二甲基氯化锡对斜生栅藻的生长均有一定抑制作用,且二甲基氯化锡的毒性大于一甲基氯化锡。当有机锡浓度为200μg.L-1时,对藻细胞的生长抑制达到20.4%;随着有机锡浓度的增加,抑制效应增大。

壶状臂尾轮虫(Brachionus urceus)培养滤液对斜生栅藻(Scenedesmus obliquus)形态和多聚糖含量的影响

分离自太湖的壶状臂尾轮虫(Brachionus urceus (Linnaeus))按1000 ind.L-1的密度置于斜生栅藻(Scenedesmus obliquus)中培养24h后,用孔径0.10μm的微孔滤膜抽滤,得到壶状臂尾轮虫培养滤液。将壶状臂尾轮虫培养滤液以20%的比例添加到纯培养的斜生栅藻中,进行为期7d的试验。结果表明壶状臂尾轮虫培养滤液能显著地影响斜生栅藻的形态,处理组中诱发性多细胞群体增加,导致处理组中斜生栅藻种群平均每个个体的细胞数量显著高于对照组。斜生栅藻在壶状臂尾轮虫诱发下形成群聚体可以解释为一种诱发性的反牧食防御,同时也进一步证实了栅藻对浮游动物牧食的响应是一种广泛存在的现象。壶状臂尾轮虫培养滤液处理后的斜生栅藻在生长率上与对照组没有显著性差异,说明诱发性防御群聚体形成的代价没有体现在对生长的影响上。在壶状臂尾轮虫培养滤液诱发下,较多栅藻细胞聚积在一起形成群聚体后,栅藻溶解性胞外多聚糖和固着性胞外多聚糖均有显著提高,而胞内多聚糖略有下降。但从总多聚糖含量看,处理组明显高于对照组,这也说明轮虫培养滤液刺激了栅藻多聚糖合成的额外增加,且被分泌到胞外,充当细胞之间的粘合物,促使细胞容易聚合形成群聚体,有效防御象轮虫这些小型浮游动物的进一步牧食,保持种群得以延续。

盐度对一株淡水栅藻Scenedesmus sp.生长及生化组成的影响

通过管式光生物反应器培养,分析比较不同盐度(0-40‰)对一株淡水栅藻(Scenedesmus sp.)生长和生化特性影响,评价海水培养该藻株的产业化潜力,探讨其高盐适应机制,为进一步海水驯化研究提供理论参考。采用显微观察、索氏提取法、凯氏定氮法、苯酚硫酸法、气相色谱法及高效液相色谱法分别测定微藻生长及蛋白质、油脂、多糖含量以及色素、脂肪酸组成情况。结果表明,高盐条件下藻细胞明显增大,并出现自然沉降现象,可实现低成本采收。随盐度增加,栅藻生长逐步被抑制,40‰盐度条件下生长完全停止,但在3‰盐度下仍良好生长,培养末期生物量可达2.84 g/L。30‰盐度组蛋白质含量相对淡水组提高95.40%、产率与淡水组相近,加之高盐培养可较大幅度降低蛋白质的生产成本,因此,采用海水培养栅藻来开发蛋白资源具有一定的潜力。研究还表明,30‰盐度下藻细胞内β-胡萝卜素、虾青素、可溶性多糖等成分大量积累,可能是其适应高盐胁迫的重要生理基础。

Effects of silica nanoparticles on growth and photosynthetic pigment contents of Scenedesmus obliquus

To assess the aquatic ecosystem safety for silica （SiO2） nanoparticles （NPs）, the growth inhibition and photosynthetic pigment contents of Scenedesmus obliquus in logarithm growth phase exposed to SiO2 NPs and SiO2 bulk particles （BPs） suspensions were measured. SiO2 NPs with 10-20 nm diameters were found to be toxic. The 20% effective concentration （EC20） values for 72 and 96 hr were 388.1 and 216.5 mg/L, respectively. The contents of chlorophyll decreased significantly under moderate and high concentration （50, 100, and 200 mg/L） of SiO2 NPs after 96-hr exposure, but the carotenoids did not. SiO2 BPs were found to be nontoxic up to 200 mg/L. The toxicity of SiO2 NPs probablely due to their sorption to algal cells surface. The results imply that there is potential harm to aquatic environment by using SiO2 NPs, and it should deserve special concern.

Salt response of the freshwater microalga Scenedesmus obliquus(Turp.)Kutz is modulated by the algal growth phase

Growth and biochemical responses of the coenobial green alga Scenedesmus obliquus to salinity stress were monitored across different phases of growth.The alga was cultured on BG11 growth medium and subjected to 0,30,100,and 200 mmol/L NaCl for a period of 20 d,during which algal cultures were harvested at 4-d intervals.The salinity-induced inhibition of algal growth was accompanied with prolongation of timing of the different growth phases.The sharp and progressive salinity-induced inhibition of algal growth rate during the early phase of growth points to salt shock but moderation of inhibition at the subsequent stages of growth means algal acclimation to salinity.The concentrations of chlorophylls a and b,soluble sugars,proteins as well as those of K+and Na+in the alga exhibited peaks at the initiation of the exponential phase of growth,with increasing magnitude in proportion to the increase in the level of salinity.Nevertheless,whereas soluble sugars of the alga peaked at initiation of the exponential phase,starch concentration progressively increased with culture age,reaching saturation towards the stationary phase.Whereas the salinity-induced increase in soluble sugars was most evident at the early stages of growth the reverse was true for starch.The present results point to fast acclimation of S.obliquus to salt stress post a brief salt shock,utilizing soluble sugars,K+and Na+for osmotic adjustment.Increasing salinity from 0 to 200 mmol/L NaCl led to progressive increase in soluble sugars,proteins,K+and Na+concentrations of the algal cells,particularly at the early stages of growth.However,the salinity-induced increase in chlorophyll concentration approached a limit at 100 mmol/L NaCl whereas that in starch concentration was more evident at the later stages of growth.

Split internal-loop photobioreactor for Scenedesmus sp.microalgae:Culturing and hydrodynamics

In this study,the evaluation of the performance of the split internal loop photobioreactor for culturing a species of green microalgae,Scenedesmus sp.under different operating superficial gas velocity and during a different time of growth(i.e.,starting for the first day until end day of the culturing process)was addressed.The evaluation of the performance of the split internal loop photobioreactor was included assessing the density,pH,temperature,viscosity,surface tension,the optical density,cell population,dry biomass,and chlorophyll of the culture medium of the microalgae culturing.Additionally,the hydrodynamics of a Split Internal-Loop Photobioreactor with microalgae culturing was comprehensively quantified.Radioactive particle tracking(RPT)and gamma-ray computed tomography(CT)techniques were applied for the first time to quantify and address the influence of microalgae culture on the hydrodynamic parameters.The hydrodynamics parameters such as local liquid velocity field,shear stresses,turbulent kinetic energy,and local gas holdup profiles were measured at different superficial gas velocities as well as under different times of algae growth.The obtained results indicate that the flow distribution may significantly affect the performance of the photobioreactor,which may have substantial effects on the cultivation process.The obtained experimental data can serve as benchmark data for the evaluation and validation of computational fluid dynamics(CFD)codes and their closures.This,in turn,allows us to develop efficient reactors and consequently improving the productivity and selectivity of these photobioreactors.

Effects of iron and humic acid on competition between Microcystis aeruginosa and Scenedesmus obliquus revealed by HPLC analysis of pigments

Iron is a vital micronutrient for growth of bloom-forming Microcystis aeruginosa and competition with other algae,and its availability is affected by humic acid.The effect of iron and humic acid on growth and competition between M.aeruginosa and Scenedesmus obliquus was assessed.The results showed the growth of M.aeruginosa and S.obliquus in mono-cultures was inhibited by humic acid at low iron concentrations(0.01 mg/L);the maximum inhibition ratios were 67.84%and 38.31%,respectively.The inhibition of humic acid on the two species was significantly alleviated when iron concentrations were 1.00 mg/L,with the maximum inhibition rate reduced to 5.82%for M.aeruginosa and to 23.06%for S.obliquus.S.obliquus was the dominant species in mixed cultures,and the mutual inhibition between M.aeruginosa and S.obliquus at low iron concentration was greater than that at high iron concentration.The inhibition of S.obliquus on M.aeruginosa was reduced at low iron concentrations;it increased at high iron concentrations,as concentrations of humic acid rose.

Infl uences of aeration induced turbulence on growth and competition of Microcystis and Scenedesmus in the presence of sediments with varying particle sizes

Aeration is an important measure to prevent cyanobacterial growth in eutrophic lakes and reservoirs.The purpose of this study is to clarify the infl uence of aeration induced turbulence on growth and competition of Microcystis and Scenedesmus in the presence of sediments with varying particle sizes.Microcystis aeruginosa and Scenedesmus obliquus were selected as the model organisms.Sediments with varying particle sizes were added into mono and mixed cultures of the organisms.In the absence of sediment,both low-and high-intensity aerations(the turbulent dissipation rates were 1.60×10^(-6)and 1.16×10^(-5)m^(2)/s^(3),respectively)promoted the growth of Scenedesmus,but the growth of Microcystis was inhibited particularly obvious under the high-intensity aeration conditions.In the presence of sediment,Scenedesmus was promoted under all aeration conditions,while Microcystis was inhibited.The inhibition rate of Microcystis decreased with the increase of sediment size when treated with low-intensity aeration in the nighttime.The highest inhibition rate of M.aeruginosa(89.2%)was identifi ed under the condition of low-intensity aeration in the nighttime with small sediment addition.Furthermore,our results indicated that the impacts of sediment-induced light intensity reduction on algal growth were insignifi cant.In the mixed culture,the growth of Microcystis was inhibited by Scenedesmus in all treatments with aeration.Our results provided a theoretical basis for the practice in controlling cyanobacteria by aeration.

Temperature-Induced Stress on Growth and Expression of Hsp in Freshwater alga Scenedesmus quadricauda

Objective To investigate the impact of various levels of sublethal temperature （26℃, 31 ℃, 33℃, 36℃, and 39℃） on growth and heat shock protein （hsp） expression in freshwater green alga Scenedesmus quadricauda. Methods Impact of selected levels of temperature on growth rate （based on optical density）, population count, chlorophyll-a and biomass of the alga was evaluated in artificial growth medium for 19 days. To determine the induction of hsp in the alga, it was exposed to selected temperature levels for 3 h and further kept for 6 h at culturing condition at 26℃. Induction of hsp was confirmed by immuno-detection followed by SDS-polyacrylamide gel electrophoresis. Results The selected growth parameters such as growth rate, population count, chlorophyll-a and biomass were reduced significantly （P〈0.001） at 39℃. However, hsp 70 expression was observed only at 39℃. Conclusion Temperature up to 36℃ may be considered as the limit of safe exposure for thermal, stress for the alga Scenedesmus quadricauda.

THE TOXICITY OF TWO NEWLY-SYNTHESIZED COMPOUNDS ON SCENEDESMUS OBLIQUUS KǖTZ

LY-04 and WSQIF are newly-synthesized compounds which were presented by the Institute of Pesticides Chemistry, Central China Normal University. LY-04 belongs to α-oxophosphonic acid derivatives, while WSQIF is an aromatic acetyl oxophosphonic acid derivative. In this study, the toxicity of LY-04 and WSQIF on Scenedesmus obliquus Kütz was examined. The EC 50 of LY-04 and WSQIF were determined in S. obliquus cells at 24h, 48h, 72h, 96h represented by cell density. Our data showed that the 24h, 48h, 72h, 96h EC 50 of LY-04 were 1983mg/L, 2943mg/L, 240mg/L and 65.0mg/L acetone, respectively, and the 24h, 48h, 72h, 96h EC 50 of WSQIF were 15.9mg/L, 53.0mg/L, 98.0mg/L and 28.8mg/L respectively. LY-04 displayed a higher insecticidal activity, while WSQIF showed a higher phytocidal activity. As LY-04 and WSQIF were designed to act as insecticide and herbicide, respectively, the results were in contrast to the anticipated ones. According to the toxicant classification standard, EC 50 of both substances was far higher than 3mg/L, while the toxicity of LY-04 and WSQIF to aquatic algae were fairly low, indicating that these two pesticides are rather safe to the aquatic ecosystem.

Nutrient Removal and Algal Community Variation from Urban River with the Isolated Microalgal Strains <i>Chlorella</i>sp. and <i>Scenedesmus</i>sp.

The objectives of this study were to determine nutrient removal rates and algal community variation using the isolated microalgal strains Chlorella sp. and Scenedesmus sp. from an urban river water. The concentration of total nitrogen (TN) and total phosphorus (TP) in river water declined after pouring into Chlorella sp. and Scenedesmus sp., it was indicated that the Scenedesmus sp. had respective advantage in removing nitrogen (86% removal rate) and Chlorella sp. in removing phosphorous (95% removal rate). The algae community composition showed extreme sensitivity to change in the joint of the Scenedesmus or Chlorella, respectively, the lower diversity and higher dominance of algae can be observed in Scenedesmus group, there existed an opposite tendency in Chlorella group. The results demonstrated that the high potential of using Chlorella sp. and Scenedesmus sp. for nutrient removal from riverwater.

Enhancement of Cell Growth and Lipid Content of a Freshwater Microalga <i>Scenedesmus</i>sp. by Optimizing Nitrogen, Phosphorus and Vitamin Concentrations for Biodiesel Production

The effects of nitrogen, phosphorus and vitamin on growth and lipid content of a freshwater microalgae Scenedesmus sp. were investigated under indoor conditions. Nitrogen, phosphorus and vitamin presented significant statistical effect on lipid content, and a maximum lipid content of 29.3% was obtained, corresponded to increases of 90% when compared to those obtained with the original nutrients medium. On the other hand, only nitrogen and phosphorus presented significant statistical effect on cell growth, achieving ash free dry biomass, algal density, and specific growth rate of 1.3 g·L-1, 1.5E+07 cells mL-1, and 0.62 d-1, respectively. By the use of the desirability function, it was possible to maximize the cell growth and lipid content simultaneously. The fatty acid composition of the microalgal lipid comprises over 80% of saturated and monounsaturated fatty acids. Thus, Scenedesmus sp. biomass could be used as suitable feedstock for biodiesel production.

Nutrients Extracted from Chicken Manure Accelerate Growth of Microalga <i>Scenedesmus obliquus</i>HTB1

Sustainable development using wastes as resources is a new paradigm. Chicken manure contains rich amounts of nitrogen and phosphorus and has been used as crop fertilizer. However, little is known about whether nutrients of chicken manure are suitable and efficient to support the rapid growth of microalgae. In this study, we explore the possibility of using nutrient extracted from chicken manure to grow microalgae. We used an algal strain Scenedesmus sp. HTB1, which is an oleaginous species with high CO2 tolerance capability. The growth performance of HTB1 on various media amended with nutrient extracted from three different chicken manure sources was monitored and compared to the growth rate of HTB1 grown in the standard medium BG11. Meanwhile, the changes of total nitrogen (N) and phosphorus (P), both organic and inorganic, were measured during the growth period. Culture media enriched with the nutrient extracted from two chicken manure sources outperformed the standard culture medium BG11 in terms of algal biomass production. When cultivated with manure nutrient, HTB1 utilized inorganic N efficiently, but consumed very little organic N during the experimental growth period. However, HTB1 was able to utilize both organic and inorganic phosphorus. We demonstrate that nutrient extracted from chicken manure support rapid growth and high biomass yield in microalgae?Scenedesmus obliquus?HTB1. Therefore chicken manure holds great promise to be used as a cost-effective and efficient fertilizer for large-scale production of microalgae.

Assessment of Biomass Productivities of Chlorella vulgaris and Scenedesmus obliquus in Defined Media and Municipal Wastewater at Varying Concentration of Nitrogen

Microalgae are emerging as one of the most promising long-term sustainable sources of renewable energy. Studies were conducted on two freshwater Chlorophytes, Chlorella vulgaris and Scenedesmus obliquus to evaluate heterotrophic growth rate and biomass productivity in filter-sterilized defined medium (BG 11) and municipal wastewater, both with varying concentrations of nitrogen (N). For each isolate, cultures were separately incubated in triplicate at room temperature with constant agitation on a shaker at 150 rpm for 9 days. In 0.25 mg N/L BG11 medium, the growth rate and biomass productivity of C. vulgaris were 0.28 day-1 and 3.5 g·L-1, respectively. In wastewater, the same amount of N addition resulted in a higher growth rate 0.44 day-1 and associated biomass productivity of 4.96 g·L-1. Increasing N levels to 0.5 mg N/L in BG11 caused an increase in growth rate (0.37 day-1) and biomass productivity (4.28 g·L-1), while the increase in N in wastewater caused growth to decline to 0.32 day-1 with decreased biomass productivity of 2.19 g·L-1. A further increase in N to 1.0 mg N/L in BG11 caused an increase in the growth rate (0.43 day-1) and a decrease in biomass productivity (3.64 g·L-1), while in wastewater, growth rate and productivity of C. vulgaris were 0.32 day-1 and 2.31 g·L-1, respectively. Overall, C. vulgaris grew faster and produced greater biomass than S. obliquus under comparable conditions. Based on high growth rate and biomass productivity of C. vulgaris, it could be a potential candidate for further consideration for simultaneous wastewater treatment and biofuel production.

Osmotic Stress Effect over Carbohydrate Production in a Native Starin of Scenedesmus sp.

The production of biofuels is currently presented as a possible answer in the search for sustainable alternatives for the total or partial substitution of fossil fuels. One of the most successful biofuels that have been developed is bioethanol. However, bioethanol production has been limited since it relies on the use of sugar cane or cereals. These materials are important sources of food and their demand as both a biofuel and a foodstuff has led to the price increase and may lead to possible shortages. Our group has focused on searching for native microalgae as sources of carbohydrates and bioethanol, with the goal of finding a sustainable source of bioethanol. Currently, twelve different strains which reach growth rates between 0.7 - 1.8 g/L and present carbohydrate production under osmotic shock conditions have been isolated. In this work, we demonstrate the results obtained with the Chlorella sp. [1] strain and the results obtained with the Scenedesmus sp. strain. The Scenedesmus sp. strain showed an increase in the production from 22 to 650 mg/sugar/g of biomass (dry weight), after 24 hours of osmotic shock with 0.1 M NaCl. The osmolytes which were produced after osmotic shock were identified as sucrose and trehalose, both of which are fermentable. These results demonstrate that this strain, through the photosynthetic pathway and osmotic shock, is a potential source of fermentable sugars.

Toxic effects of enrofloxacin on Scenedesmus obliquus

In this article, the toxic effects of Enrofloxacin （ENFX） on Scenedesmus obliquus were studied, through investigating the growth, photosynthetic pigments, and protein contents. The possible toxic mechanisms of ENFX were analyzed by determining the superoxide dismutase （SOD） activity, malondialdehyde （MDA） content, proline content, and superoxide anion （O2） generation rate. Results showed that the growth of algae was inhibited by ENFX and the 50% effective concentration （EC50） values for 24, 48, 72, and 96 h of ENFX were 88.39, 63.86, 45.10, and 59.16 mg .L^-1, respectively. After treated with ENFX for 96h, the contents of photosynthetic pigments decreased with the increase of ENFX concentration, the content of soluble protein and the activity of SOD increased and then decreased, and the generation rate of superoxide anion （O2^-） increased continually. The contents of MDA and proline changed little in lower ENFX concentration groups, but increased rapidly when treated with higher concentration groups. These results suggested that ENFX affected the growth ofS. obliquus, and the main toxicity mechanism was that algal cells generated the reactive oxygen species under ENFX stress, and then the reactive oxygen species （ROS） induced the oxidation damages of biologic macromolecules and changed the biomembrane permeability further.

Metabolites change of Scenedesmus obliquus exerted by AgNPs

With increasing emission of silver nanoparticles(AgNPs) into the environment, it is important to understand the effects of ambient concentration of AgNPs. The biological effects of AgNPs on Scenedesmus obliquus, a ubiquitous freshwater microalgae, was evaluated. AgNPs exerted a minor inhibitory effect at low doses. Non-targeted metabolomic studies were conducted to understand and analyze the effect of AgNPs on algal cells from a molecular perspective. During the 48 hr of exposure to AgNPs, 30 metabolites were identified, of which nine had significant changes compared to the control group. These include D-galactose, sucrose, and D-fructose.These carbohydrates are involved in the synthesis and repair of cell walls. Glycine, an important constituent amino acid of glutathione, increased with AgNP exposure concentration increasing, likely to counteract an increased intracellular oxidative stress. These results provide a new understanding of the toxicity effects and mechanism of AgNPs. These metabolites could be useful biomarkers for future research, employed in the early detection of environmental risk from AgNPs.

Attached cultivation of Scenedesmus sp.LX1 on selected solids and the effect of surface properties on attachment

Attached cultivation systems in the literature do not present a methodology to screen materials for microalgal growth. Hence, a method is needed to find suitable materials for attached cultivation that may enhance attachment of microalgae. In this paper, we have tested seven materials culturing Scenedesmus sp. LX1 (S. sp. LX1)to evaluate the attachment of microalgae on the material surface, its growth in suspension phase and the properties of the materials. Two materials showed attachment of S. sp. LX1, polyurethane foam and loofah sponge, and allowed microalgae to grow both in the surface of the material and suspended phase. Polyurethane foam proved to be a good material for attachment of S. sp. LX1 and the amount of attached microalgae obtained was 51.73 mg/L when adding 100 pieces/L. SEM images showed that the surface and the pore size of the materials affected the attachment of the microalgae, increasing its attachment in scaffold-like materials. Furthermore, the hydrophilic and hydrophobic properties of the materials also affected the attachment of microalgae. This research can be used as a methodology to search for the assessment of a material suitable for attachment of microalgae.

亚硝态氮对铜绿微囊藻和四尾栅藻生长的影响

采用室内培养法,将铜绿微囊藻和四尾栅藻分别置于5种含不同质量浓度亚硝态氮（NO2^--N）（0.5 mg/L、1.0 mg/L、2.0 mg/L、4.0mg/L和8.0 mg/L）的培养液中,培养10 d,测定不同质量浓度NO2^--N对铜绿微囊藻和四尾栅藻生长的影响。结果表明,0.5-8.0 mg/L的NO2^--N可激活铜绿微囊藻的亚硝酸氧化酶和亚硝酸还原酶,进而促进铜绿微囊藻的生长。四尾栅藻因仅具有亚硝酸还原酶,因此只能利用0.5-2.0 mg/L的NO2^--N,其利用能力远没有铜绿微囊藻强。培养8 d后,铜绿微囊藻培养液中NH4^＋-N和NO2^--N的质量浓度明显升高,而NO3^--N质量浓度的变化不大;四尾栅藻培养液中NH4^＋-N、NO2^--N和NO3^--N质量浓度的变化不大。研究表明,低于8.0 mg/L的NO2^--N可促进铜绿微囊藻的生长,高于2.0 mg/L的NO2^--N抑制四尾栅藻的生长。

缺氮条件对栅藻油脂积累与光合作用的影响

栅通过油脂分析、光合放氧、叶绿素荧光等手段,研究了缺氮处理对栅藻(Scenedesmus dimorphus)油脂含量、油脂组分以及光合作用影响。结果显示,总脂含量由22.4%±0.6%提高到36.3%±0.7%,其中甘油三酯含量由4.6%±1.2%提高到68.3%±2.5%而磷脂含量由92.8%±1.6%降低到26.8%±2.0%。缺氮处理1 d后,叶绿素含量明显下降,呼吸速率明显升高。缺氮处理初始阶段,栅藻光系统Ⅱ最大光能转化效率(Fv/Fm)和非光化学猝灭系数(NPQ)维持稳定,4 d后Fv/Fm显著降低而NPQ显著升高。上述变化可能是光能过剩引起的防御反应,也可能是自身代谢模式发生转变的结果而与光能耗散无关。