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PubMed2002

Treatment of recalcitrant wastewater from ethanol and citric acid production using the microalga Chlorella vulgaris and the macrophyte Lemna minuscula.

Laboratory-scale experiments were performed to develop a procedure for biological treatment of recalcitrant anaerobic industrial effluent (from ethanol and citric acid production) using first the microalga Chlorella vulgaris followed by the macrophyte Lemna minuscula. This recalcitrant dark-colored wastewater, containing high levels of organic matter and low pH, prevents the growth of microalgae and macrophytes, and therefore, could not be treated by them. Therefore, the wastewater was diluted to 10% of the original concentration with wash water from the production line. Within 4 days of incubation in the wastewater, C. vulgaris population grew from 5 x 10(5) to 2 x 10(6) cells/mL. This culture reduced ammonium ion (71.6%), phosphorus (28%), and chemical oxygen demand (COD) (61%), and dissolved a floating microbial biofilm after 5 days of incubation. Consequently, L. minuscule was able to grow in the treated wastewater (from 7 to 14 g/bioreactor after 6 days), precipitated the microalgal cells (by shading the culture), and reduced other organic matter and color (up to 52%) after an additional 6 days of incubation. However, L. minuscula did not improve removal of nutrients. This study demonstrates the feasibility of combining microalgae and macrophytes for bioremediation of recalcitrant industrial wastewater.

Anaerobiosis↗
PubMed2001

Bioconcentration of the insecticide pyridaphenthion by the green algae Chlorella saccharophila.

A study was undertaken to examine the uptake of the organophosphate insecticide pyridaphenthion in the chlorophyta Chlorella saccharophila. Algae cultures were exposed to the initial nominal concentration 10.0 mg l(-1) pyridaphention during seven days. The insecticide bioconcentrates in the biomass to the highest level of 441.5 +/- 25.9 mg kg(-1) on the fifth day of exposure and was followed by a decrease to 76.6 +/- 5.1 mg kg(-1) on the seventh day. A model was constructed to describe the dynamic process, which estimated a bioconcentration factor (BCF) equal to 28. The study demonstrates the potential of accumulation of pyridaphenthion in aquatic organisms and helps to expand the pyridaphenthion toxicity database. The replacement of fenitrothion by pyridaphenthion concerning their use in rice flooded cultures is discussed.

Absorption↗
PubMed2001

Zinc acclimation and its effect on the zinc tolerance of Raphidocelis subcapitata and Chlorella vulgaris in laboratory experiments.

The effect of zinc acclimation of Raphidocelis subcapitata (syn. Selenastrum capricornutum) and Chlorella vulgaris on their sensitivity towards this metal was examined in a series of laboratory experiments. These two commonly used algal species were acclimated to 65 microg Zn/l and changes in zinc tolerance were monitored using standard growth inhibition tests. The chemically defined ISO medium was used as a control culture medium. Both species demonstrated a maximum increase in zinc tolerance of a factor of 3 after 100 days of acclimation. Shifts in the shape of the concentration-response curve due to acclimation were observed for R. subcapitata. Compared to non-acclimated algae, acclimated R. subcapitata exhibited higher growth rates in all zinc treatments as well as in the controls. This suggests that the use of ISO-medium results in sub-optimal growth due to zinc deficiency. These effects could not be demonstrated for C. vulgaris. The zinc tolerance of both species decreased significantly one week after returning the acclimated algae to control (ISO) medium. 72hEC50 values based on growth rate were two to four times higher than those calculated using biomass measurements. Algal toxicity test results, particularly if used for metal risk assessments, must not be conducted using nutrient deficient media.

Acclimatization↗
PubMed2000

Microcalorimetric studies on the metabolism of Chlorella vulgaris.

The heat output of the non-growth metabolism of Chlorella vulgaris has been determined using an LKB-2277 BioActivity Monitor. The experimental results indicate that there is a turn-point on the metabolic thermogenic curves, which can be divided into two parts, an early phase and a later phase. For the early phase, there is a linear relationship between the metabolic power (P) and the cell concentration (C), and that the heat output produced by a single cell's metabolism (P0) depends on the cell concentration (C) and is inhibited by the cell density, the thermokinetic equation of their metabolism is dP/dt = k0, k0 = 0.

Calorimetry, Indirect↗
PubMed2003

Effect of three nitrophenols on carbon metabolism in Nostoc muscorum and Chlorella vulgaris.

Carbon metabolism in selected strains of Nostoc muscorum and Chlorella vulgaris grown in the presence of three nitrophenols [o-nitrophenol, m-nitrophenol and 2,4-dinitrophenol] was assessed by examining activities of the enzymes such as amylase, starch phosphorylase, fructose 1,6-biphosphatase, sucrose phosphate synthase, and invertase. Marked alterations were observed in activities of the enzymes involved in starch metabolism. The cellular content of starch in nitrophenol-grown cultures was significantly reduced, whereas the levels of nonreducing and reducing sugars significantly increased. There was a significant increase in the activities of amylase and phosphorylase, and these alterations are probably responsible for the decreased amount of starch in the cultures. Furthermore, significant changes were noticed in activities of the enzymes involved in synthesis of sucrose as well.

Amylases↗
PubMed1997

Effect of hot water extract of Chlorella vulgaris on cytokine expression patterns in mice with murine acquired immunodeficiency syndrome after infection with Listeria monocytogenes.

We have previously reported that oral administration of hot water extract of Chlorella vulgaris (CVE) enhances resistance to Listeria monocytogenes through augmentation of Listeria-specific cell-mediated immunity in normal mice and mice with murine acquired immunodeficiency syndrome (MAIDS) caused by murine leukemia virus (MuLV) LP-BM5. To elucidate the mechanisms whereby CVE augments the cell-mediated immunity, we examined the expression patterns of mRNA for cytokines in normal and MAIDS mice given CVE orally after L. monocytogenes infection. The expression levels of IL-1 alpha, IL-12, GM-CSF, MIP and TNF alpha genes were significantly augmented in the peritoneal adherent cells by oral administration of CVE for 2 weeks before Listeria infection. The expression levels of gamma IFN and IL-12 mRNA were significantly higher in the spleen after Listeria infection in CVE-treated mice than in normal mice, while the expression of IL-10 mRNA in the spleen was decreased by CVE administration. In MAIDS mice, oral administration of CVE also augmented the expression of gamma IFN and IL-12 mRNA in the spleen after Listeria infection, while it rather reduced the expression of IL-10 mRNA. These results suggest that CVE may preferentially augment THI responses against Listeria via activation of macrophages to produce IL-12 and enhance host defence against Listeria infection both in normal and MAIDS mice.

Animals↗
PubMed2002

Physiological response of freshwater microalga (Chlorella vulgaris) to triazine and phenylurea herbicides.

The effects of two herbicides used wide-spread, isoproturon (phenylurea) and terbutryn (triazine), on growth, dry weight, elemental composition, photosynthetic pigments and protein content, and cell volume assayed by flow cytometry in the freshwater microalgae Chlorella vulgaris were studied. Different parameters for algal activity show widely different sensitivities to these aquatic pollutants. After 96 h of herbicide exposure, terbutryn was the strongest inhibitor of growth, giving an EC50 value for growth twice lower than that for isoproturon cultures (EC50 terbutryn=0.097 microM; EC50 isoproturon=0.199 microM). However, lower concentrations of the triazine herbicide provoked an increase in the cellular density and growth rate of this microalga, not observed in the phenylurea-treated cultures. Cellular volume and dry weight of C. vulgaris cells were increased strongly in the presence of isoproturon and terbutryn. Other cellular parameters, such as pigment and protein content, were stimulated with both herbicides at higher concentrations.

Adaptation, Physiological↗
PubMed2002

The effect of water hardness on the toxicity of uranium to a tropical freshwater alga Chlorella sp.

Uranium (U) derived from mining activities is of potential ecotoxicological concern to freshwater biota in tropical northern Australia. Few data are available on the effects of water hardness (Ca and/or Mg), which is elevated in U mine wastewaters, on the toxicity and bioavailability of U to freshwater biota, particularly algae. This study determined the effect of water hardness (8, 40, 100 and 400 mg CaCO(3) x l(-1), added as calcium (Ca) and magnesium (Mg) sulphate) on the toxicity (72 h growth rate inhibition) of U to the unicellular green alga, Chlorella sp., in synthetic freshwater, at constant pH (7.0) and alkalinity (8 mg CaCO(3) x l(-1)), similar in chemical composition to sandy coastal streams in tropical northern Australia. A 50-fold increase in water hardness resulted in a 5-fold decrease (P 0.05) differences in the predicted speciation (% distribution) of U amongst the four water hardness levels. The reduction in U toxicity with increasing water hardness was most likely due to competition between U and Ca and/or Mg for binding sites on the algal cell surface. The minimum detectable effect concentrations of U were approximately 3 and 24 times higher (at 8 and 400 mg CaCO(3)x l(-1) hardness, respectively) than the national interim U guideline value (0.5 micro g x l(-1)) for protecting aquatic ecosystems. Overall, the results reinforce the need for a more flexible U guideline based on a hardness-dependent algorithm, which may allow environmental managers to relax the national guideline for U on a site-specific basis.

Biological Availability↗
PubMed1998

1H and 13C NMR studies of a truncated heme domain from Chlorella vulgaris nitrate reductase: signal assignment of the heme moiety.

A water soluble truncated heme domain (a tetramer of MW = 45 kDa) of the tetrameric nitrate reductase complex from the green alga Chlorella vulgaris has been overexpressed and purified. This truncated heme domain with four identical subunits has a high redox potential (midpoint potential E1/2 = +16 mV) as compared with other heme-containing flavoproteins. We have undertaken a determination of the detailed configuration of the heme moiety in order to understand the unique electrochemical property of the heme moiety of this enzyme. We report here the study of the heme prosthetic group of the truncated heme domain by the use of 2D 1H and 13C NMR techniques. A complete signal assignment of the heme has been achieved. Our observations suggest that the heme configuration is similar to that of the crystal structure of the membrane-bound bovine liver cytochrome b5.

Animals↗
PubMed2000

Chlorella vulgaris culture supernatant (CVS) reduces psychological stress-induced apoptosis in thymocytes of mice.

A glycoprotein prepared from Chlorella vulgaris culture supernatant (CVS) is a biological response modifier (BRM) which exhibits protective activities against tumor metastasis and 5-fluorouracil-induced immunosuppression. We here show that oral administration of CVS prevented significantly the apoptosis of thymocytes in mice undergoing psychological stress in a communication box. Mice were exposed to the emotional stress for 14 days by witnessing other mice being exposed to foot-shock. The numbers in thymocytes, especially CD4(+)CD8(+) population, were decreased significantly and apoptotic cells, as assessed by Annexin V expression, were reciprocally increased after the exposure to the psychological stress. C. vulgaris culture supernatant (CVS) administration significantly suppressed the increase in serum corticosterone level in the psychologically stressed mice. These results suggest that CVS prevents psychological stress and maintain homeostasis in the face of external environmental changes.

Animals↗
PubMed1999

Oral administration of hot water extracts of Chlorella vulgaris reduces IgE production against milk casein in mice.

Hot water extract of Chlorella vulgaris (CVE) is a biological response modifier (BRM) which enhances resistance to Listeria monocytogenes through augmentation of helper T cell type 1 (Thl) responses producing gamma-interferon (gammaIFN). We show here that oral administration of CVE in mice suppressed the production of immunoglobulin (Ig)E against casein antigen accompanied by increased gammaIFN and IL-12 mRNA expression. Oral administration of CVE enhanced Thl response to casein in the spleen of casein immunized mice. CVE may be useful for prevention of allergic diseases with a predominant Th2 response.

Administration, Oral↗
PubMed1999

Effects of Chlorella vulgaris on bone marrow progenitor cells of mice infected with Listeria monocytogenes.

In this study we investigated the effects of the treatment with Chlorella vulgaris extract (CVE) on the hematopoietic response of granulocyte-macrophage colony-forming unit (CFU-GM) of mice infected with a sublethal dose of Listeria monocytogenes (1 x 10(4) organisms/animal). CVE was given orally as 50 mg/kg/day for 5 days. In the CVE treated/infected groups L. monocytogenes was administered at the end of CVE treatment. The colony stimulating activity of the serum (CSA) was also studied in all groups. Although no effects on CFU-GM, as compared to controls, were observed in the groups receiving CVE alone, the extract produced an increase in CSA levels as compared to controls. On the other hand, the presence of the infection led to a significant reduction in the numbers of CFU-GM as observed at 48 and 72 h after the infection, in spite of the significant increase in serum CSA activity. CVE treatment of infected animals restored the numbers of CFU-GM to control levels. In the treated/ infected group the increased serum CSA was significantly higher than that observed in the only infected group. The CVE treatment (50 and 500 mg/kg) of mice infected with a dose of 3 x 10(5) bacteria/animal, which was lethal for all the non-treated controls, produced a dose-response protection which led to a 20 and 52% survival, respectively. These results demonstrated that CVE produces a significant increase in the resistance of the animals infected with L. monocytogenes, and that this protection is due, at least in part, to increased CFU-GM in the bone marrow of infected animals.

Administration, Oral↗
PubMed2003

Comparative characteristic of mitochondria ultrastructural organization in Chlorella cells under altered gravity conditions.

Results from experiments that used cells from the unicellular alga Chlorella vulgaris (strain Larg-1) grown on a clinostat, demonstrated the occurrence of rearrangements in cellular organelles, including changes in the mitochondrial ultrastructure compared to controls. Changes in mitochondrial structure were observed in auto- and heterotrophic regimes of cells grown in altered gravity conditions, especially in long-term experiments. The mitochondrial rearrangements become apparent during cell proliferation, which resulted in an increase in the relative volume of mitochondria per cell: up to 2.7 +/- 0.3% in short-term clino-rotation (2.2 +/- 0.1% in the control) and up to 5.3 +/- 0.4% and 5.1 +/- 0.4% in long-term clinorotation (2.3 +/- 0.2% in the control). The size of the mitochondria and their cristae increased in cells grown under long-time clinorotation. In addition, hypertrophied organelles, not typical for this strain, were observed. These changes in the cells were accompanied by increased electron density of the matrix and a well-ordered topography of the cristae. To examine the separation of oxidative phosphorylation and respiration, an inhibitory agent 2,4-dinitrophenol (2,4-DNP) was applied to cells which resulted in insignificant volume changes of the mitochondria (2.5 +/- 0.4% versus 2.1 +/- 0.2% in the control). The increase of mitochondrial size with regularly arranged cristae, with more condensed matrix and extension of cristae areas of clino-rotated cells, may demonstrate higher functional activity of the mitochondria under altered gravity conditions. Changes observed early in clinorotated cells, in particular the increased level of respiration, adenylate content (especially ATP) and more intensive electron-cytochemical reactions of Mg2(+)-ATPase and succinate [correction of succinat] dehydrogenase (SDH) in mitochondria (including hypertrophic organelles), also suggest increased activity of mitochondria from cells grown under altered gravity conditions compared to controls.

2,4-Dinitrophenol↗
PubMed1975

[The effect of SH group inhibitors on phosphate transport in Chlorella pyrenoidosa].

The effect of Sulphydryl reagents have been investigated. pCMB inhibits the transport of phosphate in Chlorella pyrenoidosa. This inhibition is immediate and does not change as a function of time of incubation. This inhibition affects non starved and starved cells (phosphate omitted). pCMPS and Mersalyl act in the same manner as pCMB. When these compounds are used at low concentrations, inhibition of phosphate uptake is observed only in starved cells. The substrate (phosphate) cannot provide protection against this inhibition. NEM inhibits phosphate uptake and this inhibition increases as a function of time of incubation. When the time of incubation is very short (about 15 seconds) the effects seems to be superficial and NEM reacts with SH groups involved in the transport system. When phosphate is present (for 15 seconds of incubation with NEM) the inhibition is less important than when phosphate is omitted. The substrate protects against NEM, but this protection disappears as the incubation with NEM is prolonged. NEM inhibits phosphate uptake in non starved and starved cells, however, it is observed that the inhibition is less important in starved cells than in non starved cells. The authors conclude that two kinds of SH groups might exist in the phosphate transport system, one reacting with pCMB and the other with NEM.

4-Chloromercuribenzenesulfonate↗
PubMed2000

Kinetics of uptake of cadmium by Chlorella marina in different media.

The kinetics of cadmium binding to living Chlorella marina cells during a short time (a few minutes) has been studied in seawater conditions, being also considered separately the influence of calcium and chloride. Cadmium complexes with surface groups of C. marina cells are labile in terms of differential pulse anodic stripping voltammetry in media (0.01-0.7) M NaNO3 since the complexation reaction is kinetically fast. However, in media 0.7 M NaCl, 0.7 M NaCl + 10(-2) M Ca2- and in synthetic seawater diluted 1:4 or not, the complexes are inert, since kinetics is determined by the rate of exchange with alkaline-earth metals and/or the chloride anion.

Cadmium↗
PubMed1999

Thermodynamics of uptake of cadmium by Chlorella marina.

From voltammetric titration curves of living Chlorella marina cells with cadmium ion, at constant pH, the surface binding capacity of the alga was determined and interpreted in terms of average conditional equilibrium constants and of differential equilibrium function. Since the alga can live in estuaries, the influence of ionic strength and competition of alkaline and alkaline earth cations has been considered. Cadmium complexation with dead algae killed by heat or using formaldehyde has also been studied for comparison.

Algorithms↗
PubMed2003

Optical whole-cell biosensor using Chlorella vulgaris designed for monitoring herbicides.

An optical biosensor was designed for determination of herbicides as aquatic contaminants. Detection was obtained with immobilised Chlorella vulgaris microalgae entrapped on a quartz microfibre filter and placed in a five-membrane-home-made-flow cell. The algal chlorophyll fluorescence modified by the presence of herbicides was collected at the tip of an optical fibre bundle and sent to a fluorimeter. A continuous culture was set up to produce algal cells in reproducible conditions for measurement optimisation. Effects of flow rate, algal density, temperature, and pH on the biosensor response to atrazine were studied. Reversibility and detection limits were determined for DNOC and atrazine, simazine, isoproturon, diuron. Detection of photosystem II (PSII) herbicides was achieved at sub-ppb concentration level.

Atrazine↗
PubMed2003

Chlorella sorokiniana immobilized on the biomatrix of vegetable sponge of Luffa cylindrica: a new system to remove cadmium from contaminated aqueous medium.

A new sorption system of microalgal cells immobilized on the biostructural matrix of Luffa cylindrica for sequestering cadmium is reported. Free and immobilized Chlorella sorokiniana removed cadmium from 10 mgl(-1) solution at the efficiency of 92.7% and 97.9% respectively. Maximum cadmium sorption was observed to be 39.2 mgg(-1) at equilibrium (C(eq)) of 112.8 mgl(-1) by immobilized microalgal biomass as compared to 33.5 mgg(-1) at C(eq) of 116.5 mgl(-1) by free biomass from initial concentration of 150 mgl(-1). In continuous liquid flow column, the cadmium sorption capacity of immobilized C. sorokiniana was 192 mgg(-1), which was 73.2% of the total metal passed in 51.5 l. Metal desorption with 0.1 M HCl was 100% and the desorbed immobilized system was reusable with a similar efficiency in the subsequent cycle.

Adsorption↗