Freshwater Microalga Scenedesmus Research Articles

Morpho-physiological effects of ibuprofen on Scenedesmus rubescens

The pollution of aquatic bodies by drugs is an emerging environmental problem, because of their extensive use in animal and human context. Ibuprofen, 2-[4-(2-methylpropyl)phenyl]propanoic acid, is the non-steroidal anti-inflammatory drug mainly present both in wastewater and in rivers and lakes in Europe. Since in literature there is little information about the effects of ibuprofen on microalgae, in this paper we presented the results on the effects of this molecule at different concentrations (62.5μgL−1, 250μgL−1 and 1000μgL−1) on cultures of the freshwater microalga Scenedesmus rubescens (P.J.L. Dangeard) E. Kesslet et al. Ibuprofen effects on the alga were assayed at first through analyses of the growth curve. Moreover, analyses of cell morphology, ultrastructure, and photosynthetic pigments were additionally performed. The first negative effect of the drug was on the microalga growth, suggesting a drug action dose-dependent mechanism type, more evident at the concentration of 1000μgL−1 ibuprofen and in the last phase of the growth curve. In support of this, following ibuprofen exposure, the cells exhibited morphological and ultrastructural alterations, mainly consisting in large cytoplasmic inclusions, probably of lipids and/or carotenoids. The decrease of chlorophyll amounts and, on the contrary, the increase of carotenoids were correlated with a stressful condition induced by drug.

Identification and characterization of a freshwater microalga Scenedesmus SDEC-8 for nutrient removal and biodiesel production

The selection of the right strains is of fundamental important to the success of the algae-based oil industry. From the six newly isolated microalgae strains tested for growth, fatty acid methyl ester (FAME) profiles and biodiesel properties, Scenedesmus SDEC-8, with favorable C16:0 fatty acids (73.43%), showed the best combined results. Then, morphological and molecular identification were examined. From the three wastewaters samples, Scenedesmus SDEC-8 showed good ability to yield oil and remove nutrients, which were comparable with other reports. In b artificial wastewater (TN 40 mg L(-1), TP 8 mg L(-1)), Scenedesmus SDEC-8 achieved the highest value of lipid productivity (53.84 mg L(-1) d(-1)), MUFA content (35.35%) and total FAME content (59.57±0.02 mg g(-1) DW), besides higher removal efficiencies of TN (99.18%) and TP (98.86%) helped effluent directly discharge and smaller dilution factor of N, P (3.3 and 9) which was good for lessening water utilization.

Effect of indigo dye effluent on the growth, biomass production and phenotypic plasticity of Scenedesmus quadricauda (Chlorococcales)

The effect of indigo dye effluent on the freshwater microalga Scenedesmus quadricauda ABU12 was investigated under controlled laboratory conditions. The microalga was exposed to different concentrations of the effluent obtained by diluting the dye effluent from 100 to 175 times in bold basal medium (BBM). The growth rate of the microalga decreased as indigo dye effluent concentration increased (p <0.05). The EC50 was found to be 166 dilution factor of the effluent. Chlorophyll a, cell density and dry weight production as biomarkers were negatively affected by high indigo dye effluent concentration, their levels were higher at low effluent concentrations (p <0.05). Changes in coenobia size significantly correlated with the dye effluent concentration. A shift from large to small coenobia with increasing indigo dye effluent concentration was obtained. We conclude that even at low concentrations; effluents from textile industrial processes that use indigo dye are capable of significantly reducing the growth and biomass production, in addition to altering the morphological characteristics of the freshwater microalga S. quadricauda. The systematic reduction in the number of cells per coenobium observed in this study further confirms that environmental stress affects coenobium structure in the genus Scenedesmus, which means it can be considered an important biomarker for toxicity testing.

Cellular responses and bioremoval of nonylphenol and octylphenol in the freshwater green microalga Scenedesmus obliquus

The removal of nonylphenol (NP) and octylphenol (OP) by the freshwater green microalga Scenedesmus obliquus was studied in cultures exposed to different concentrations of NP and OP for 5 days. In most cases, low NP and OP concentrations (<1mg/L) did not affect the growth, fluorescence transient (Fv/Fm), photosynthetic pigments and cell ultrastructure of S. obliquus, whereas high NP and OP concentrations (>1mg/L) suppressed algal growth, decreased Fv/Fm and photosynthetic pigments, and destroyed algal ultrastructure. S. obliquus had a rapid and high ability to remove NP and OP. After 5 days of culturing, >89 percent NP and >58 percent OP were removed by this alga, with the highest removal efficiency being near 100 percent. The removal of NP and OP was mainly caused by algal degradation. Extracellular NP contents of S. obliquus were lower than intracellular NP contents, with the ratios changing from 0 to 0.74. However, most of extracellular OP contents of S. obliquus were higher than intracellular OP contents, with the ratios changing from 0.74 to 2.15. The two alkylphenols exhibited a high bioconcentration potential, with one-day bioconcentration factors (BCF) of NP and OP varying between 3393 to 13262 and 949 to 3227, respectively. After 5 days of culturing, high BCF values were still recorded when NP and OP initial concentrations were higher than 0.5mg/L. These results demonstrated potential application of this algal species in the removal of organic contaminants including alkylphenols in addition to nutrients and metals.

Accumulation characteristics of soluble algal products (SAP) by a freshwater microalga Scenedesmus sp. LX1 during batch cultivation for biofuel production

Algae cultivation is the essential basis for microalgal biofuel production. Soluble algal products (SAP) are significant obstacle to large-scale, high-cell-density cultivation processes. SAP accumulation during batch cultivation of Scenedesmus sp. LX1 (a unique strain accumulating lipid substantially while growing fast under low-nutrient conditions) with different initial nitrogen concentrations (7.4–34.0mgNL−1) was investigated. The SAP content varied in the range of 3.4–17.4mgDOCL−1 at stationary phase, with average yield per cell of 0.5–2.5pgDOCcell−1. High SAP accumulation up to 15.2–17.4mgDOCL−1 were observed with initial nitrogen above 20.2mgNL−1. The maximum SAP production rate per unit culture volume (rSAP) was 2.6mgDOC(Ld)−1 and that per cell (νSAP) was 1.5pgDOC(celld)−1. The rSAP increased with cell growth rate and decreased with cell density linearly. The SAP accumulation was majorly due to the release of growth-associated products.

Growth and lipid accumulation properties of a freshwater microalga Scenedesmus sp. under different cultivation temperature

Microalgal lipid is a promising feedstock for biodiesel production. Effect of cultivation temperature on the growth and lipid accumulation properties of a freshwater microalga Scenedesmus sp. LX1 was studied. Scenedesmus sp. LX1 could grow in a wide range of temperature (10∼30°C), and the growth activation energy was 49.3 kJ·mol(-1). The optimal temperature to produce microalgal biomass and lipid was 20°C, and after 15 days of batch cultivation the productivities of 313.3 g biomass·(g P)(-1), 112 g lipid (g P)(-1) and 14.7 g TAGs·(g P)(-1) were obtained. The content of polyunsaturated fatty acids decreased with the increase of cultivation temperature. The reactive oxygen species (ROS) levels at 10°C and 20°C were higher than that under higher temperature. For the first time the cultivation temperature, ROS level, specific growth rate and lipid content per microalgal biomass were correlated together.

Effects of different nitrogen and phosphorus concentrations on the growth, nutrient uptake, and lipid accumulation of a freshwater microalga Scenedesmus sp.

Microalgae have high potential to remove inorganic nutrients from wastewater and to produce biodiesel. Effects of nitrogen and phosphorus concentrations on growth, nutrient uptake, and lipid accumulation of a freshwater microalga Scenedesmus sp. LX1 were studied. Scenedesmus sp. LX1’s growth was in accordance with the Monod model. The following Monod parameters were obtained: the N- and P-saturated maximum growth rate was 2.21 × 10 6 cells mL −1 d −1, and the half-saturation constants of N and P uptake were 12.1 mg L −1 and 0.27 mg L −1, respectively. In the nitrogen/phosphorus ratio of 5:1–12:1, 83–99% nitrogen and 99% phosphorus could be removed. In conditions of nitrogen (2.5 mg L −1) or phosphorus (0.1 mg L −1) limitation, Scenedesmus sp. LX1 could accumulate lipids to as high as 30% and 53%, respectively, of its algal biomass. The lipid productivity/unit volume of culture, however, was not enhanced. Further research should be made on how to enhance both lipid content and lipid productivity.

Growth and nutrient removal properties of a freshwater microalga Scenedesmus sp. LX1 under different kinds of nitrogen sources

Microalgae have received much attention for the inorganic nutrient removal in tertiary treatment of domestic wastewater. Effect of different kinds of nitrogen sources on the growth and nitrogen/phosphorus removal properties of a newly isolated freshwater microalga, Scenedesmus sp. LX1, from a low-nutrient environment condition was studied and reported in this paper. The order of specific growth rate of the microalga with different nitrogen sources was NH 4-N > urea-N > NO 3-N. With nitrate or urea as nitrogen source, the microalga could grow well and remove both nitrogen and phosphorus efficiently (90% nitrogen and nearly 100% phosphorus were removed). However, with ammonium as the nitrogen source, the maximum algal density was relatively low, and the nitrogen and phosphorus removal efficiencies were as low as 31.1% and 76.4%, respectively. This was caused by the inhibitory effect of algal culture's acid pH due to H + releasing from NH 4 + during algal cultivation process.

Effects of norfloxacin and butylated hydroxyanisole on the freshwater microalga Scenedesmus obliquus

The toxic effects of norfloxacin (NOR) and butylated hydroxyanisole (BHA) on the microalga Scenedesmus obliquus were assessed in terms of growth rate, concentration of chlorophyll a, activities of 7-ethoxyresorufin-o-dealkylases (EROD), glutathione s-transferase (GST), catalase (CAT) and total malondialdehyde content (MDA). The 96 h EC(50) was 38.49 and 11.12 mg/l for NOR and BHA, respectively. Growth of S. obliquus was affected slightly under low concentrations of BHA (<4 mg/l) and NOR (<15 mg/l) over the 96 h exposure period. With the increasing concentrations of these two compounds, growth of S. oblique decreased significantly. Growth inhibition was 82.4% at 60.0 mg/l for NOR and 60.6% at 16.0 mg/l for BHA after 96 h. A similar trend was also observed for chlorophyll alpha. NOR and BHA affected Phase I and Phase II enzyme activities differently. Upon exposure to NOR, EROD was induced at concentration <15.0 mg/l and depressed at concentrations >30 mg/l significantly. CAT and GST exhibited similar trends during the exposure period. Compared to controls, MDA content only showed high induction at high concentrations of NOR (>30 mg/l). However, EROD activity did not display any change compared to control responses during BHA exposure, whereas GST showed significant induction for all concentrations over the exposure period. CAT activity showed induction at low concentration and depression at high concentration. MDA content increased with the rise of BHA during the exposure period. These types of assays, revealing toxic effects of NOR and BHA to phototrophs, could be employed to assess the potential risks of these xenobiotics to aquatic ecological systems.

Toxicity of ionic copper to the freshwater microalga Scenedesmus acuminatus (Chlorophyceae, Chlorococcales)

A.T. Lombardi, T.M.R. Hidalgo, A.A.H. Vieira and A.L. Sartori. 2007. Toxicity of ionic copper to the freshwater microalga Scenedesmus acuminatus (Chlorophyceae, Chlorococcales). Phycologia 46: 74–78. DOI: 10.2216/06-40.1Metal ecotoxicity testing with microalgae is subject to interferences such as change in bioavailable metal fraction by excreted metabolites. Moreover, high metal loads are usually necessary for obtaining 50% effect concentration (EC50) values based on cell number or chlorophyll a. Thus, sensitive parameters, which promptly respond to low dissolved metal variations at environmentally relevant concentrations, are much needed. The genus Scenedesmus, a coenobium-forming freshwater microalga, is cosmopolitan and inhabits pristine and contaminated waters. The present investigation addressed cellular phenotypic alterations in Scenedesmus acuminatus (Largerheim) Chodat 1902 caused by the presence of copper. Copper toxicity to the alga was investigated under laboratory-controlled conditions using a concentration range of 10−8 mol l−1 to 10−3 mol l−1 total dissolved Cu2+, thus including environmentally relevant concentrations. Free Cu2+ concentrations were determined using an ion-selective electrode calibrated with a metal ion buffer. The phenotypic plasticity of S. acuminatus was measured as the number of cells per coenobia and found to be readily affected at low copper concentrations. Under healthy conditions (10−8 mol l−1 total dissolved Cu2+, 10−11 mol l−1 free Cu2+) S. acuminatus formed eight-celled coenobia, whereas at 10−7 mol l−1 total dissolved Cu2+ (3 × 10−10 mol l−1 free Cu2+) these were absent and at 10−5 mol l−1 total dissolved Cu2+ (5 × 10−8 mol l−1 free Cu2+) free cells were predominant. Chlorophyll a synthesis was affected by 5 × 10−8 mol l−1 free Cu2+ or higher. EC50 (3.3 × 10−5 mol l−1 free Cu2+) was obtained using chlorophyll a values after 96-h exposure to the toxicant. The number of cells per coenobia was a more sensitive parameter than chlorophyll a to assess Cu toxicity, and at concentrations that may be encountered in the environment.

The adsorption kinetics of metal ions onto different microalgae and siliceous earth

In the present work the adsorption kinetics of the six metal ions aluminum, zinc, mercury, lead, copper, and cadmium onto living microalgae were measured. The freshwater green microalga Scenedesmus subspicatus, the brackish water diatom Cyclotella cryptica, the seawater diatom Phaeodactylum tricornutum, and the seawater red alga Porphyridium purpureum were the subject of investigation. In most cases the adsorption rate of the metals could be well described by using the equation of the Langmuir adsorption rate expression. Inverse parameter estimation allowed the determination of the rate constants of the adsorption process and the maximum metal content of the algae. The highest values for the rate constant were obtained for Porphyridium purpureum followed by Phaeodactylum tricornutum. High values for the maximum content were obtained for Cyclotella cryptica and Scenedesmus subspicatus. The maximum rate constant was 24.2 l h −1 for the adsorption of Hg to Porphyridium purpureum whereas the maximum metal content (0.243 g g −1) was obtained for Zn on Cyclotella cryptica. A comparison of these values with those obtained for the mineral siliceous earth exhibiting low maximum content and high adsorption rates reveals that the mechanism of adsorption onto the algae is a mixture of adsorption and accumulation.

Influence of phosphorus concentration and temperature on growth and phosphorus uptake by the microalga Scenedesmus obliquus

The growth of the freshwater microalga Scenedesmus obliquus has been studied in a mineral medium with P concentrations of between 0 and 372 μM and temperatures of 20, 25, 30 and 35°C. At all the temperatures, growth was inhibited by the P. The inhibition by P was highly dependent on temperature, detected at concentrations on the order of 1 μM at 35°C, 2 μM at 20 and 25°C, and 350 μM at 30°C. The greatest specific growth rate, 0.047 h −1, was registered at 30°C. The specific growth rates were adjusted to a semistructured model of inhibition by the substrate. The inhibition constants, K 1 (μM), increased with rising temperatures from 20 to 25 and 30°C, and decreased at higher temperatures. At 35°C, the lowest value was recorded for K 1 1.20 μM, and thus the inhibitory effect was the most pronounced. At 30°C, within the interval of P concentrations of 0–300 μM, it was possible for the variation in μ S 0 to be fitted to a semistructured Monod kinetic model of limitation by the substrate. Yield of biomass varied with temperature. The highest yields were reached at 20°C. The specific rates of P consumption increased with S 0, tending towards a constant value. The highest values, obtained at 30°C and 35°C, were practically the same, and the lowest were obtained at 20°C.

Influence of phosphorus concentration on the growth kinetics and stoichiometry of the microalga Scenedesmus obliquus

The growth of the freshwater microalga Scenedesmus obliquus was studied at 30°C in a mineral culture medium with phosphorus concentrations of between 0 and 372 μ m. The values for the specific growth rates, between S 0=0 μ m and S 0=298 μ m , fitted a semistructured substrate-limitation model with μ m1 = 0·0466 h −1, μ m2 = 0·0256 h −1 and K S = 0·2 μ m . The specific uptake rate of phosphorus reached a maximum value of q Sm1 = 658·01 × 10 −4 μmol P mg −1 biomass h −1.

Wastewater nutrient removal with microalgae immobilized in carrageenan

Two species of the green freshwater microalga Scenedesmus have been immobilized in beads of κ-carrageenan. Growth curves were similar to those observed with free cells. The uptake of nitrogen and phosphorus from wastewater was similar for free and entrapped microalgae. The reduction of N-NH + 4 was 90% within 4 h at pH 9.0 and 70% within 5 h at an adjusted pH of ∼7.7. From these experiments, we conclude that immobilized Scenedesmus microalgae can grow well within gel beads and that they are as physiologically active for wastewater nutrient removal as free cells.