Growth Of Algal Cells Research Articles

An in situ method for synthesis of magnetic nanomaterials and efficient harvesting for oleaginous microalgae in algal culture

An in situ approach for magnetic nanomaterial synthesis and harvesting of oleaginous Chlorella sp. HQ in an algal culture was explored. Fe-based nanomaterials were synthesized by an in situ reduction reaction using NaBH4 and FeCl3∙6H2O in an algal culture. The various reactant molar ratios and the reaction system of a water solution or an algal culture determined the different formation pathways of magnetic nanomaterials. With the optimal reactant molar ratio of 2:1, this in situ magnetic harvesting method obtained a high harvesting efficiency in a broad pH and temperature range and different algal concentration levels with cost of $505 US per ton of algal biomass harvested. During this in situ process, the algal antioxidant defense system efficiently eliminated the cellular reactive oxygen species caused by nanomaterials via catalase and superoxide dismutase. Fatty acid methyl ester composition analysis indicated that the Fe-based nanomaterials affected the relative contents of several components, but the predominant types were still palmitic acid (C16:0), linoleic acid (C18:2) and γ-linoleic acid (C18:3), which were suitable for biofuel production. Additionally, the recycled cultivation medium maintained normal algal cell growth within 18 days after the biomass had reached the harvesting level. This novel in situ method has promising potential for the harvest of oleaginous microalgae with good biocompatibility.

Responses of unicellular alga Chlorella pyrenoidosa to allelochemical linoleic acid

Linoleic acid (LA), is the product of secondary metabolism secreted from Microcystis aeruginosa, and it exhibits allelopathic activity against eukaryotic algae. However, information about on the mechanisms associated with the inhibition of algal activity by LA is limited. In this study, Chlorella pyrenoidosa was treated with LA (20–120 μg L−1) for 4 days, and its growth inhibition and physiological responses were examined for potential toxic mechanisms. The photosynthetic efficiency of C. pyrenoidosa was inhibited by LA treatments, and the Fv/Fm parameter decreased significantly compared to that of controls; however, the photosynthetic pigment content did not change significantly. Peroxidase activity was enhanced, relieving oxidative damage in algae after LA treatments. However, superoxide dismutase and catalase were suppressed, ultimately leading to the aggravation of lipid peroxidation. Transcriptome-based gene expression analysis revealed that the 120 μg L−1 LA treatment significantly inhibited the transcription of genes related to photosynthesis, carbon metabolism, and amino acid metabolism in C. pyrenoidosa, suggesting that these genes might be key LA targets in C. pyrenoidosa. Moreover, the expression of genes involved in vitamin, lipid, nitrogen cycling, terpenoid, and ascorbate metabolism was also affected, suggesting that LA inhibits algal cell growth through multiple pathways. The identification of LA-responsive genes in C. pyrenoidosa provides new insight into LA stress responses in eukaryotic algae.

Evaluation of the toxic response induced by azoxystrobin in the non-target green alga Chlorella pyrenoidosa.

The top-selling strobilurin, azoxystrobin (AZ), is a broad-spectrum fungicide that protects against many kinds of pathogenic fungi by preventing their ATP production. The extensive use of AZ can have negative consequences on non-target species and its effects and toxic mechanisms on algae are still poorly understood. In this work, Chlorella pyrenoidosa that had been grown in BG-11 medium was exposed to AZ (0.5-10mgL-1) for 10d. The physiological and molecular responses of the algae to AZ treatment, including photosynthetic efficiency, lipid peroxidation level, antioxidant enzyme activities, as well as transcriptome-based analysis of gene expression, were examined to investigate the potential toxic mechanism. Results shows that the photosynthetic pigment (per cell) increased slightly after AZ treatments, indicating that the photosystem of C.pyrenoidosa may have been strengthened. Glutathione and ascorbate contents were increased, and antioxidant enzyme activities were induced to relieve oxidative damage (e.g., from lipid peroxidation) in algae after AZ treatment. Transcriptome-based analysis of gene expression combined with physiological verification suggested that the 5mgL-1 AZ treatment did not inhibit ATP generation in C.pyrenoidosa, but did significantly alter amino acid metabolism, especially in aspartate- and glutamine-related reactions. Moreover, perturbation of ascorbate synthesis, fat acid metabolism, and RNA translation was also observed, suggesting that AZ inhibits algal cell growth through multiple pathways. The identification of AZ-responsive genes in the eukaryotic alga C.pyrenoidosa provides new insight into AZ stress responses in a non-target organism.

Physicochemical characteristics and toxicity of surface-modified zinc oxide nanoparticles to freshwater and marine microalgae

Because of wide applications of surface-modified zinc oxide nanoparticles (ZnO-NPs) in commercial sunscreens and their easiness of being released into water, concerns have been raised over their potential effects on aquatic organisms. This study compared physicochemical properties of silane-coated and uncoated ZnO-NPs to elucidate their toxic potencies toward three freshwater and three marine microalgae. Surfaces of ZnO-NPs (20 nm) were modified by coating with 3-aminopropyltrimethoxysilane (A-ZnO-NPs) that provides the particles with a more hydrophilic surface, or dodecyltrichlorosilane (D-ZnO-NPs) that turns the particles to hydrophobic. Uncoated ZnO-NPs formed larger aggregates and released more Zn2+ than did either of the two coated ZnO-NPs. The three nanoparticles formed larger aggregates but released less Zn2+ at pH 8 than at pH 7. Although sensitivities varied among algal species, A-ZnO-NPs and uncoated ZnO-NPs were more potent at inhibiting growth of algal cells than were D-ZnO-NPs after 96-h exposure to ZnO, uncoated ZnO-NPs, each of the coated ZnO-NPs or ZnSO4 at 10 concentrations ranging from 0.1 to 100 mg/L. The marine diatom Thalassiosira pseudonana exposed to ZnO-NPs, A-ZnO-NPs or D-ZnO-NPs resulted in differential expressions of genes, suggesting that each of the coatings resulted in ZnO-NPs acting through different mechanisms of toxic action.

Optogenetic regulation of artificial microRNA improves H2 production in green alga Chlamydomonas reinhardtii

BackgroundChlamydomonas reinhardtii is an ideal model organism not only for the study of basic metabolic processes in both plants and animals but also the production of biofuels including hydrogen. Transgenic analysis of C. reinhardtii is now well established and very convenient, but inducible exogenous gene expression systems remain under-studied. The most commonly used heat shock-inducible system has serious effects on algal cell growth and is difficult and costly to control in large-scale culture. Previous studies of hydrogen photoproduction in Chlamydomonas also use this heat-inducible system to activate target gene transcription and hydrogen synthesis.ResultsHere we describe a blue light-inducible system with which we achieved optogenetic regulation of target gene expression in C. reinhardtii. This light-inducible system was engineered in a photosynthetic organism for the first time. The photo-inducible heterodimerizing proteins CRY2 and CIB1 were fused to VP16 transcription activation domain and the GAL4 DNA-binding domain, respectively. This scheme allows for transcription activation of the target gene downstream of the activation sequence in response to blue light. Using this system, we successfully engineered blue light-inducible hydrogen-producing transgenic alga. The transgenic alga was cultured under red light and grew approximately normally until logarithmic phase. When illuminated with blue light, the transgenic alga expressed the artificial miRNA targeting photosynthetic system D1 protein, and altered hydrogen production was observed.ConclusionsThe light-inducible system successfully activated the artificial miRNA and, consequently, regulation of its target gene under blue light. Moreover, hydrogen production was enhanced using this system, indicating a more convenient and efficient approach for gene expression regulation in large-scale microalgae cultivation. This optogenetic gene control system is a useful tool for gene regulation and also establishes a novel way to improve hydrogen production in green algae.

Effect of pH on Biohydrogen Production in Green Alga Tetraspora sp. CU2551

The green alga Tetraspora sp. CU2551 has previously been identified as a hydrogen producing organism. With the promising potential in a high H2 production yield, we further studied the enhancement of the H2 production capacity by a substrate-level control to the key enzyme, Hydrogenase. This enzyme catalyzes the formation of biohydrogen gas from protons and electrons. Here, we investigated the effect of pH on the production rate which directly affected the flow of proton flux to the hydrogenase enzyme. The result revealed that pH of culture TAP medium was simply controlled by the use of HCl/NaOH solution over the pH range of 6.5 - 9.0 without any effect on the growth of algal cells. The H2 production was observed in all ranges of our focusing pH with comparable to the control condition (pH 7.0 of TAP medium). In our best condition, an increase of the H2 yield about 24% was found in cells cultivated in TAP medium adjusted the pH to 6.5 compared to the control condition. Our finding confirms the successful biohydrogen production enhancement by a substrate-level control for the key hydrogenase enzyme.

Bacterial Associates Modify Growth Dynamics of the Dinoflagellate Gymnodinium catenatum.

Marine phytoplankton cells grow in close association with a complex microbial associate community known to affect the growth, behavior, and physiology of the algal host. The relative scale and importance these effects compared to other major factors governing algal cell growth remain unclear. Using algal-bacteria co-culture models based on the toxic dinoflagellate Gymnodinium catenatum, we tested the hypothesis that associate bacteria exert an independent effect on host algal cell growth. Batch co-cultures of G. catenatum were grown under identical environmental conditions with simplified bacterial communities composed of one-, two-, or three-bacterial associates. Modification of the associate community membership and complexity induced up to four-fold changes in dinoflagellate growth rate, equivalent to the effect of a 5°C change in temperature or an almost six-fold change in light intensity (20–115 moles photons PAR m-2 s-1). Almost three-fold changes in both stationary phase cell concentration and death rate were also observed. Co-culture with Roseobacter sp. DG874 reduced dinoflagellate exponential growth rate and led to a more rapid death rate compared with mixed associate community controls or co-culture with either Marinobacter sp. DG879, Alcanivorax sp. DG881. In contrast, associate bacteria concentration was positively correlated with dinoflagellate cell concentration during the exponential growth phase, indicating growth was limited by supply of dinoflagellate-derived carbon. Bacterial growth increased rapidly at the onset of declining and stationary phases due to either increasing availability of algal-derived carbon induced by nutrient stress and autolysis, or at mid-log phase in Roseobacter co-cultures potentially due to the onset of bacterial-mediated cell lysis. Co-cultures with the three bacterial associates resulted in dinoflagellate and bacterial growth dynamics very similar to more complex mixed bacterial community controls, suggesting that three-way co-cultures are sufficient to model interaction and growth dynamics of more complex communities. This study demonstrates that algal associate bacteria independently modify the growth of the host cell under non-limiting growth conditions and supports the concept that algal–bacterial interactions are an important structuring mechanism in phytoplankton communities.

温度和营养盐限制对网状原角藻生长与产毒的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 温度和营养盐限制对网状原角藻生长与产毒的影响 DOI: 10.5846/stxb201605200974 作者: 作者单位: 国家海洋局第一海洋研究所 青岛,国家海洋局第一海洋研究所 青岛,国家海洋局第一海洋研究所 青岛,国家海洋局第一海洋研究所 青岛,国家海洋局东海预报中心 上海,国家海洋局第一海洋研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金（41206161）；海洋公益性行业科研专项经费项目（201305010）；国家海洋局第一海洋研究所基本科研业务专项资金项目（2012T08， GY2013G28）；国家基金委-山东省联合基金项目"海洋生态与环境科学"（U1406403）；青岛市创业创新领军人才项目计划（13-CX-28） Effects of temperature and nutrient limitation on growth and yessotoxin production of Protoceratium reticulatum Author: Affiliation: First Institute of Oceanography, SOA,,,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:网状原角藻（Protoceratium reticulatum）是能够形成有毒赤潮的海洋甲藻之一，所产毒素为虾夷扇贝毒素（yessotoxins， YTXs），该藻在全球很多海域中普遍存在，其生长与产毒特征表现出较强的海域差异性。以分离自我国北黄海海域的网状原角藻为实验对象，研究了温度和营养盐（N、P）限制对该藻生长与产毒的影响。研究发现：温度和营养盐限制对藻细胞的生长和产毒均有影响，但营养盐限制影响更为显著。较低的温度更适宜P.reticulatum的生长，15℃时无营养盐限制的L1-Si培养基中藻细胞生长最好。营养盐限制尤其是P限制能够显著降低藻细胞的比生长速率和细胞密度（P < 0.01），缩短藻细胞指数生长期和稳定期的持续时间。所有温度下N、P限制均有利于藻细胞内毒素累积，15℃ P限制培养基中单个藻细胞中YTX毒素最高，达到92.6 pg/细胞，分别是相同培养温度下N限制和L1-Si中藻细胞毒素含量的3.8倍和7.1倍。温度变化对N和P限制下藻细胞毒素含量影响不同：在5-15℃范围内，随温度升高，N限制培养基中藻细胞YTX含量增幅逐渐下降，而P限制条件下反之。在所有培养条件下，滤液中毒素含量在稳定期后开始增多，与L1-Si相比，N、P限制不利于毒素的释放。高温能促进L1-Si培养基和N限制培养基中毒素的释放，但对P限制影响不显著。 Abstract:Protoceratium reticulatum,a marine dinoflagellate that produces yessotoxins (YTXs), is common in coastal waters worldwide and can form toxic algal blooms. There are marked differences in its growth and toxin-producing characteristics in different areas. This study investigated the effects of temperature and nutrient (N, P) limitation on the growth and toxin production of P. reticulatum recently isolated from the North Yellow Sea. The results showed that temperature and nutrient limitation affected growth and toxin production of the alga to different degrees, but nutrient limitation had a more significant influence. Lower temperatures were more suitable for the growth of P. reticulatum. Growth of algal cells in L1-Si medium without nutrient limitation was best at 15℃. P limitation greatly reduced the specific growth rate and cell density (P < 0.01), and shortened the duration of the exponential and stationary phases. N-limited cultures, in contrast, resulted in a growth rate and maximum cell density similar to those in L1-Si medium, but with a shorter stationary phase. At all temperatures, both N and P limitation were favorable for the accumulation of YTX in algal cells, which was particularly marked in the latter. The maximum YTX content of 92.6pg/cell was observed in 1/10P medium at 15℃ at the end of the stationary phase. This was approximately 3.8 times and 7.1 times that of the YTX in the N limited and L1-Si medium at the same culture temperature, respectively. Changes in temperature had different influences on the content of intracellular YTX in N-and P-limitation cultures. In the range of 5-15℃, temperature change had a negative effect on YTX increase under N limitation, whereas in P-limited medium, the effect was positive. In all culture conditions, the YTX concentration in the filtrate began to increase during the stationary phase. Compared with L1-Si, both N-and P-limited media were not conducive to the release of toxins. Higher temperature helpful to YTX release in the L1-Si and N-limited media, but it did not significantly affect that in the P-limited medium. 参考文献 相似文献 引证文献

A Method to Prepare Magnetic Nanosilicate Platelets for Effective Removal of Microcystis aeruginosa and Microcystin-LR.

Algal toxin is a unique type of toxin generated with harmful algal blooms in water bodies. This phenomenon is worsened by eutrophication caused by excessive discharge of nutrients into surface water bodies. Since algal toxins are hard to remove after they enter the water treatment processes, an efficient method is required to inhibit the growth of algal cells, to settle the cells at the bottom of the water body and to removes the toxin from the water. We report an efficient way to prepare a novel nanohybrid material, i.e., magnetic nanosilicate platelet (MNSP), and its effects on the removal of microcystin toxins as well as the cells of Microcystis aeruginosa. MNSP was fabricated by a special treatment of a clay mineral, montmorillonite, and then its surface was decorated with magnetite nanoparticles by in situ synthesis. The nanohybrid can efficiently inhibit the growth of M. aeruginosa-a typical species that can generate one of the most notorious algal toxins, i.e., microcystins. Algal cells can be settled with minimal 500 ppm MNSP, and the turbidity can be reduced by more than 67%. The removal of microcystin-LR (MC-LR) was as high as 99.39% at an concentration of 100 ppm, while the pristine nanosilicate platelet could only remove 36.84% at the same dosage.

Inhibitory effects of tributyl phosphate on algal growth, photosynthesis, and fatty acid synthesis in the marine diatom Phaeodactylum tricornutum.

The widely used solvent extractant, tributyl phosphate (TBP), primarily used as a solvent for the conventional processing of nuclear fuel, has come under scrutiny recently due to concerns surrounding potential environmental contamination and toxicity. In this study, we found that, in Phaeodactylum tricornutum, administration of TBP severely inhibited algal cell growth by reducing photosynthetic efficiency and inducing oxidative stress. We further explored the effect of TBP by examining the gene expression of the photosynthetic electron transport chain and its contribution to reactive oxygen species (ROS) burst. Our data revealed that TBP affected both fatty acid content and profile by regulating the transcription of genes related to glycolysis, fatty acid biosynthesis, and β-oxidation. These results demonstrated that TBP did in fact trigger the synthesis of ROS, disrupting the subcellular membrane structure of this aquatic organism. Our study brings new insight into the fundamental mechanism of toxicity exerted by TBP on the marine alga P. tricornutum.

Utilization of pyrolytic substrate by microalga Chlamydomonas reinhardtii: cell membrane property change as a response of the substrate toxicity.

Acetic acid derived from fast pyrolysis of lignocellulosic biomass is a promising substrate for microalgae fermentation for producing lipid-rich biomass. However, crude pyrolytic acetic acid solution contains various toxic compounds inhibiting algal growth. It was hypothesized that such an inhibition was mainly due to the cell membrane damage. In this work, the cell membrane property of algal cells was evaluated at various conditions to elucidate the mechanisms of inhibition caused by the pyrolytic substrate solution. It was found that acetic acid itself served a carbon source for boosting algal cell growth but also caused cell membrane leakage. The acetic acid concentration for highest cell density was 4g/L. Over-liming treatment of crude pyrolytic acetic acid increased the algal growth with a concurrent reduction of cell membrane leakage. Directed evolution of algal strain enhanced cell membrane integrity and thus increased its tolerance to the toxicity of the crude substrate. Statistical analysis shows that there was a significant correlation between the cell growth performance and the cell membrane integrity (leakage) but not membrane fluidity. The addition of cyto-protectants such as Pluronic F68 and Pluronic F127 enhanced the cell membrane integrity and thus, resulted in enhanced cell growth. The transmission electron microscopy (TEM) of algal cells visually confirmed the cell membrane damage as the mechanism of the pyrolytic substrate inhibition. Collectively, this work indicates that the cell membrane is one major reason for the toxicity of pyrolytic acetic acid when being used for algal culture. To better use this pyrolytic substrate, cell membrane of the microorganism needs to be strengthened through either strain improvement or addition of membrane protectant reagents.

Effects of the timing of a culture temperature reduction on the comprehensive metabolite profiles of Chlorella vulgaris

This study investigated the effects of different temperature conditions on the comprehensive metabolite profiles of Chlorella vulgaris using gas chromatography–mass spectrometry coupled with multivariate statistical analysis. C. vulgaris cells cultivated at 20 °C were transferred to 10 °C incubators at different time points of cultivation [days 0 (TR0D), 7 (TR7D), and 14 (TR14D)], then they were cultivated at 10 °C until harvesting at day 21 to compare the growth and comprehensive metabolite profiles with those cultivated under a constant cultivation temperature of 20 °C (T20). There was no significant difference in algal cell growth between cultivation under the T20 and temperature reduction (TR) conditions. Algal fatty-acid profiles under TR were different from those of the T20 condition. Specifically, the contents of octadecanoic acid (C18:0), octadecenoic acid (C18:1), hexadecadienoic acid (C16:2), and octadecadienoic acid (C18:2) increased the most under TR0D. The relative levels of metabolites such as β-alanine, glutamine, glycine, isoleucine, proline, valine, and myo-inositol, which act as osmolytes, and bioactive compounds such as neophytadiene and ascorbic acid were increased under TR conditions on day 21. Among the metabolites, the contents of neophytadiene and ascorbic acid were further investigated, and the content of ascorbic acid was highest on day 14 under the TR7D condition, while the content of neophytadiene was highest on day 21 under the TR0D and TR14D condition. Therefore, we suggest that a TR from 20 to 10 °C could enhance the production in C. vulgaris cultures of bioactive fatty acids such as C18:1, C16:2, and C18:2 (TR0D), organic osmolytes such as β-alanine, glutamine, glycine, isoleucine, proline, valine, and myo-inositol (TR conditions), ascorbic acid (TR7D), and neophytadiene (TR0D and TR14D).

Change in Photosystem II Photochemistry During Algal Growth Phases of Chlorella vulgaris and Scenedesmus obliquus.

Sensitivity of photosynthetic processes towards environmental stress is used as a bioanalytical tool to evaluate the responses of aquatic plants to a changing environment. In this paper, change of biomass density, chlorophyll a fluorescence and photosynthetic parameters during growth phases of two microalgae Chlorella vulgaris and Scenedesmus obliquus were studied. The photosynthetic growth behaviour changed significantly with cell age and algae species. During the exponential phase of growth, the photosynthesis capacity reached its maximum and decreased in ageing algal culture during stationary phase. In conclusion, the chlorophyll a fluorescence OJIP method and the derived fluorescence parameters would be an accurate method for obtaining information on maximum photosynthetic capacities and monitoring algal cell growth. This will contribute to more understanding, for example, of toxic actions of pollutants in microalgae test.

Validation of algal viability treated with total residual oxidant and organic matter by flow cytometry

Algal cell growth after starch and oxidant treatments in seawater species (Isochrysis galbana and Phaeodactylum tricornutum) and freshwater species (Selenastrum capricornutum and Scenedesmus obliquus) were evaluated by flow cytometry with fluorescein diacetate (FDA) staining to determine algal viability. Growth of algal cell was found to be significantly different among groups treated with NaOCl, starch and/or sodium thiosulfate, which are active substance (Total Residual Oxidant; TRO as Cl2), organic compound to meet efficacy testing standard and neutralizer of TRO by Ballast Water Management Convention of International Maritime Organization, respectively. The viability of algal cell treated with TRO in starch-add culture of 5days after treatment and neutralization was decreased significantly. ATP contents of the treated algal cells corresponded to the FL1 fluorescent signal of flow cytometry with FDA staining. I. galbana was the most sensitive to TRO-neutralized cultures during viability analysis.

Enzyme activity highlights the importance of the oxidative pentose phosphate pathway in lipid accumulation and growth of Phaeodactylum tricornutum under CO2 concentration.

BackgroundRising CO2 concentration was reported to increase phytoplankton growth rate as well as lipid productivity. This has raised questions regarding the NADPH supply for high lipid synthesis as well as rapid growth of algal cells.ResultsIn this study, growth, lipid content, photosynthetic performance, the activity, and expression of key enzymes in Calvin cycle and oxidative pentose phosphate pathway (OPPP) were analyzed in the marine diatom Phaeodactylum tricornutum under three different CO2 concentrations (low CO2 (0.015 %), mid CO2 (atmospheric, 0.035 %) and high CO2 (0.15 %)). Both the growth rate and lipid content of P. tricornutum increased significantly under the high CO2 concentration. Enzyme activity and mRNA expression of three Calvin cycle-related enzymes (Rubisco, 3-phosphoglyceric phosphokinase (PGK), phosphoribulokinase (PRK)) were also increased under high CO2 cultivation, which suggested the enhancement of Calvin cycle activity. This may account for the observed rapid growth rate. In addition, high activity and mRNA expression of G6PDH and 6PGDH, which produce NADPH through OPPP, were observed in high CO2 cultured cells. These results indicate OPPP was enhanced and might play an important role in lipid synthesis under high CO2 concentration.ConclusionsThe oxidative pentose phosphate pathway may participate in the lipid accumulation in rapid-growth P. tricornutum cells in high CO2 concentration.

Reduction in toxicity of wastewater from three wastewater treatment plants to alga (Scenedesmus obliquus) in northeast China

The toxicity of municipal wastewater to the receiving water bodies is still unknown, due to the lack of regulated toxicity based index for wastewater discharge in China. Our study aims at gaining insight into the acute toxic effects of local municipal wastewater on alga, Scenedesmus obliquus. Four endpoints, i.e. cell density, chlorophyll-A concentration, superoxide dismutase (SOD) activity and cell membrane integrity, of alga were analyzed to characterize the acute toxicity effects of wastewater from municipal wastewater treatment plants (WWTPs) with different treatment techniques: sequencing batch reactor (SBR), Linpor and conventional activated sludge. Influent and effluent from each treatment stage in these three WWTPs were sampled and evaluated for their acute toxicity. Our results showed that all three techniques can completely affect the algal chlorophyll-A synthesis stimulation effects of influent; the algal cell growth stimulation effect was only completely removed by the secondary treatment process in conventional activated sludge technique; toxic effects on cell membrane integrity of two influents from WWTPs with SBR and conventional activated sludge techniques were completely removed; the acute toxicity on SOD activity was partially reduced in SBR and conventional activated sludge techniques while not significantly reduced by Linpor system. As to the disinfection unit, NaClO disinfection enhanced wastewater toxicity dramatically while UV radiation had no remarkable influence on wastewater toxicity. Our results illustrated that SOD activity and chlorophyll-A synthesis were relatively sensitive to municipal wastewater toxicity. Our results would aid to understand the acute toxicity of municipal wastewater, as well as the toxicity removal by currently utilized treatment techniques in China.

Effect of nitrogen source in low‐cost media on biomass and lipid productivity of Nannochloropsis salina for large‐scale biodiesel production

A major cost component for large‐scale algal cultivation is the medium. In this study, a significantly higher growth rate was found for Nannochloropsis salina in an inexpensive medium of seawater and agricultural fertilizer than was reached in the f/2 medium. A key difference between this new low‐cost medium and the f/2 medium is the nitrogen source. In the conditions tested herein, with aeration using air, biomass productivity reached 0.5496 g L−1 day−1 after 10 days in the low‐cost medium compared with 0.1215 g L−1 day−1 in the f/2 medium. The lipid productivity of algae grown in the low‐cost medium was also higher than that in the f/2 medium (0.1281 g L−1 day−1 versus 0.0432 g L−1 day−1). The strong linear correlation (R2 = 0.9721) between chlorophyll content and biomass concentration demonstrated that this new medium can support healthy and consistent growth of algal cells. The results suggest that it would be preferable to feed the algae for large‐scale biodiesel production with agricultural waste stream or untreated swine wastewater containing high levels of ammonia rather than treated effluent in which the ammonia/urea has been oxidized to nitrate. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 297–303, 2015

Removal of nitrogen and phosphorus from municipal wastewater effluent using Chlorella vulgaris and its growth kinetics

Chlorella vulgaris was used for the removal of residual ammonia/ammonium ion (NH3/) and orthophosphate ion () from secondary wastewater effluent collected from a municipal wastewater treatment plant. The uptake rates for nitrogen and phosphorus were studied with different initial algal cell densities and the addition of CO2 gas for pH control and supply of inorganic carbon. Our result showed that typical NH3/ and concentrations could be readily removed within 48 h. It was found that the culture with an initial algal cell density of ∼350 mg/L and CO2 gas supply could significantly enhance both the rates of cell growth and nutrient uptake. The Monod equation well described the algal cell growth under substrate-limiting conditions, and could be used for the design and operation of photobioreactors for potential tertiary wastewater treatment.

Community level physiological study of algicidal bacteria in the phycospheres of Skeletonema costatum and Scrippsiella trochoidea

Bacteria in the phycosphere have a unique ecological relationship with host algae due to their utilization of algal extracellular products as nutrients. Some bacteria control the growth of algal cells and even lyse them. The diversity of bacteria and their community dynamics in the phycosphere of microalgae are still relatively little understood, especially of those associated with red tide-causing algae. In this study, scanning electron microscope (SEM) images of algal cell morphology revealed that the phycosphere bacteria of the red tide-causing algae, Skeletonema costatum and Scrippsiella trochoidea, could lyse them within 72h. The community level physiology of the algicidal bacteria was studied using Biolog ECO microplates, a common method for the ecological study of microbial communities. The average well color development (AWCD) values of bacteria in the phycospheres of both species were low, indicating that the bacteria had low metabolic activity overall. The diversity indices were both lower than the bacterial diversity from natural environments. However, the bacteria associated with S. trochoidea demonstrated a higher AWCD value and diversity than those in the phycosphere of S. costatum. The utilization of carbon sources significantly changed at different lytic times, reflecting that the bacterial community structure changed during the algae-lysing process. These results revealed that the bacterial communities in phycospheres had a simple structure and low diversity. When the balance between algae and bacteria broke down, the total bacterial density increased while the algicidal bacteria accumulated and became the dominant species, changing the bacterial community structure in this micro-ecosystem.

Toxicity of Copper Oxide Nanoparticles on the Green Algae: &lt;i&gt;Chlorella pyrenoidosa&lt;/i&gt;

The toxicity of CuO engineered nanoparticles (ENPs) to chlorella pyrenoidosa was investigated in this study. CuO ENPs inhibited the growth of algal cells significantly, while the Cu ion and CuO bulk particles (BPs) showed lower toxicity than ENPs. The black dots observed in cells using Transmission electron microscopic (TEM) were determined as copper compound by EDS analysis. Cu content in algal cells measured confirmed the Cu internalized.