Freshwater Green Alga Chlorella Research Articles

Freshwater green alga Chlorella sp. KLSc59 produced all forms of omega-3 oil: ALA, EPA, and DHA

Omega-3 fats are known to be the essential nutrient for human health, obtainable only through food sources. Algae and phytoplankton are primary sources that can synthesize various useful metabolites, such as carotenoids, antioxidants, and omega-3 oil. As the trend toward healthy alternative food options grows, this study aimed to screen eight strains of freshwater microalgae that might be promising sources of omega-3 oil. The results showed that three algal strains-BNG2, Chlorella sp. KLSc59, and Chlorella sp. KLSc61-had the ability to produce all forms of omega-3 oil, including alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). Among these strains, Chlorella sp. KLSc59 exhibited the most consistent omega-3 fatty acids-production when detected with gas chromatography equipped with flame ionization detector. Under optimal conditions (30 % flask volume, 10 mM CaCl2, pH of 6.0, and light incubation at 162 μmol photons m−2 s−1) for 5 days, Chlorella sp. KLSc59 produced the highest amount of omega-3 fat, yielding 21.74 ± 0.63 % of the total peak area (equivalent to 18.43 ± 0.6 μg/mg DCW), including 21.53 ± 0.66 % (equivalent to 18.26 ± 0.7 μg/mg DCW) ALA, 0.03 ± 0.2 % (equivalent to 0.02 ± 0.0 μg/mg DCW) EPA, and 0.18 ± 0.01 % (equivalent to 0.15 ± 0.0 μg/mg DCW) DHA, with an omega-6 to omega-3 ratio of 2.28. This study highlights the potential use of Chlorella sp. KLSc59 for omega-3 oil production and its role as an alternative source of omega-3 oil for the next generation.

Differences in the response of Chlorella pyrenoidosa to three antidepressants and their mixtures in different light-dark start cycles.

The use of antidepressants is increasing along with the continuing spike in the prevalence of depression worldwide. As a result, more and more antidepressants are entering the water and probably does harm to the aquatic organisms and even human health. Therefore, three antidepressants, including fluoxetine (FLU), citalopram (CIT), and aspirin (APC), were selected to investigate the toxic risks of antidepressants and their mixtures to a freshwater green alga Chlorella pyrenoidosa (C. pyrenoidosa). Due light is critical for the growth of green algae, six different light-dark cycle experiments were constructed to investigate the differences in toxicity and interaction responses of C. pyrenoidosa to antidepressants and their ternary mixture designed by the uniform design ray method. The toxic effects of individual antidepressants and their mixtures on C. pyrenoidosa were systematically investigated by the time-dependent microplate toxicity analysis (t-MTA) method. Toxicity interactions (synergism or antagonism) within mixtures were analyzed by the concentration addition (CA) and the deviation from the CA model (dCA) models. The results showed that the toxicities of the three antidepressants were different, and the order was FLU > APC > CIT. Light-dark cycles obviously affect the toxicity of three antidepressants and their combined toxicity interaction. Toxicity of the three antidepressants increases with the duration of light but decreases with the duration of darkness. The ternary antidepressant mixture exhibits antagonism, and the longer the initial lighting is, the stronger the antagonism. The antagonism of the ternary mixture is also affected by exposure time and mixture components' pi as well as exposure concentration.

Effects of harvesting on morphological and biochemical characteristics of microalgal biomass harvested by polyacrylamide addition, pH-induced flocculation, and centrifugation

The effects of microalgae harvesting methods on microalgal biomass quality were evaluated using three species namely the freshwater green alga Chlorella vulgaris, marine red alga Porphyridium purpureum and marine diatom Phaeodactylum tricornutum. Harvesting efficiencies of polyacrylamide addition, alkaline addition, and centrifugation ranged from 85 to 95, 59–92 and 100%, respectively, across these species. Morphology of the harvested cells (i.e. compromised cell walls) was significantly impacted by alkaline pH-induced flocculation for all three species. Over 50% of C. vulgaris cells were compromised with alkaline pH compared to < 10% with polyacrylamide and centrifugation. The metabolic profiles varied depending on harvesting methods. Species-specific decrease of certain metabolites was observed. These results suggest that the method of harvest can alter the metabolic profile of the biomass amongst the three harvesting methods, polyacrylamide addition showed higher harvesting efficiency with less compromised cells and higher retention of industry important biochemicals.

Cultivation of Microalgae in Unsterile Malting Effluent for Biomass Production and Lipid Productivity Improvement

Microalgae have the potential to grow in nutrient-rich environments and have the ability to accumulate nutrients from wastewater. The nutrients in malting wastewater are ideal for microalgae cultivation. However, there is limited published work on the growth characteristics of freshwater microalgae grown in malting effluent. This study examined the potential of diluted malting effluent for the growth of freshwater green algae Chlorella sp. and Chlamydomonas sp. isolated from northern Ontario and subsequent biomass and lipid production. Under the 18:6 h light/dark cultivation cycle, the highest cell number counted (540 × 104 cell·mL−1 on day 20) and total chlorophyll content were found in 50% diluted malting effluents for Chlorella sp., whereas the 70% dilution concentration was the most productive for Chlamydomonas (386 × 104 cell·mL−1 on day 16). The total lipid content was higher in the 50% dilution concentration of malting effluent in both Chlorella sp. (maximum 20.5%–minimum 11.5% of dry weight) and Chlamydomonas sp. (max 39.3%–min 25.9% of dry weight). These results emphasize the suitability of using unsterile diluted malting effluent for microalgae cultivation.

Structural characterization of the photosystems in the green alga Chlorella sorokiniana.

The supramolecular organization of the photosystem supercomplexes in the green alga Chlorella sorokiniana belonging to Trebouxiophyceae are essentially the same as those of Chlamydomonas reinhardtii belonging to Chlorophyceae. The photosynthetic conversion of light energy into chemical energy is performed by photosystems II and I (PSII and PSI) embedded within the thylakoid membranes. In plants and green algae, PSII and PSI comprise the core complex and light-harvesting complexes (LHCII and LHCI), forming PSII-LHCII and PSI-LHCI supercomplexes, respectively. The structural information about photosystem supercomplexes of green algae has been limited to chlorophytic algae. Here, to obtain an insight into the evolution of Chlorophyta, we determined the supramolecular organization of the PSII-LHCII and PSI-LHCI supercomplexes from the freshwater green alga Chlorella sorokiniana, which belongs to Trebouxiophyceae. The obtained results showed that the supramolecular organizations of the photosystem supercomplexes in C. sorokiniana were essentially the same as those of the model green alga C. reinhardtii, which belongs to Chlorophyceae, namely PSII-LHCII supercomplex formed the C2S2M2L2 configuration and PSI-LHCI supercomplex was associated with 10 LHCI subunits.

Time-course effects of Tris(1,3-dichloro-2-propyl) phosphate (TDCPP) on Chlorella pyrenoidosa: Growth inhibition and adaptability mechanisms

Tris(1,3-dichloro-2-propyl) phosphate (TDCPP), a widely used chlorinated organophosphorus flame retardant, is an increasingly widespread contaminant of aquatic environment. In this study, time-dependent effect of TDCPP on the freshwater green-algae Chlorella pyrenoidosa was investigated and its underlying mechanisms were explored. We show that TDCPP lower than 10 ppm caused a reversible inhibition of algal growth, with complete inhibition occurring at 15 ppm. This inhibition was not caused by damage from reactive oxygen species, but rather resulted from the impairment of photosynthetic function, with PSII reaction center as the primary target, as indicated by Chl a fluorescence induction, QA− reoxidation, S-state distribution and immunoblot analysis. The reversal of damage caused by TDCPP concentrations under 10 ppm might be attributable to the repair of photosynthetic function by de novo protein biosynthesis in the chloroplast, with the most likely explanation being the replacement of the damaged PSII D1 protein. The results provide novel insights into mechanisms of TDCPP toxicity toward freshwater microalgae and better understanding of ecological consequences of TDCPP in the environment.

Preconcentration with Chlorella vulgaris combined with energy dispersive X-ray fluorescence spectrometry for rapid determination of Cd in water.

Freshwater green algae Chlorella vulgaris was selected as an adsorbent, and a simple, rapid, economical and environmentally friendly method for the detection of heavy metal Cd in water samples based on preconcentration with C. vulgaris combined with energy dispersive X-ray fluorescence (EDXRF) spectrometry was proposed. Chlorella vulgaris could directly and rapidly adsorb Cd2+ without any pretreatment, and the maximum adsorption efficiency could be obtained when the contact time was 1 min with an optimal pH of 10. The obtained Cd-enriched thin samples after preconcentration with C. vulgaris by suction filtration of reaction solution had very good uniformity, which could be directly measured by EDXRF spectrometry, and the net integral fluorescence intensity of Cd Kα characteristic peak had a very good linear relationship with the initial concentration of Cd in the range of 0.703–74.957 µg ml−1 with a correlation coefficient of 0.9979. When the Cd thin samples with a Cd-enriched region of 15.1 mm in diameter were formed by the developed preconcentration method with suction filtration of 10 ml reaction solution, the detection limit of this method was 0.0654 µg ml−1, which was lower than the maximum allowable discharge concentration of Cd in various industrial wastewaters. The proposed method was simple to operate, and could effectively remove the influence of matrix effect of water samples and effectively improve the sensitivity and stability of EDXRF spectrometry directly detecting heavy metals in water samples, which was successfully applied to detect Cd in real water samples with satisfactory results, and the recoveries ranged from 94.80% to 116.94%. Moreover, this method can be applied to the rapid detection and early warning of excessive Cd in discharged industrial wastewaters. This work will provide a methodological basis for the development of rapid and online monitoring technology and instrument of heavy metal pollutants in water.

Using a freshwater green alga Chlorella pyrenoidosa to evaluate the biotoxicity of ionic liquids with different cations and anions.

With the extensive use of ionic liquids (ILs) in various industrial fields, their potential toxicity to aquatic ecosystem has attracted considerable attention. In this work, biotoxicity of ILs with different cations and anions was evaluated by using a freshwater green alga Chlorella pyrenoidosa. Results showed that 1-butyl-3-methylimidazolium chloride ([C4mim]Cl), 1-octyl-3-methylimidazolium chloride ([C8mim]Cl), 1-octyl-3-methylimidazolium nitrate ([C8mim]NO3), 1-octyl-3-methylimidazolium tetrafluoroborate ([C8mim]BF4), and 1-dodecyl-3-methylimidazolium chloride ([C12mim]Cl) had a significant inhibition on the algal growth with EC50 values of 23.48, 4.72, 3.80, 4.44, and 0.10mgL-1 at the 72h of exposure, respectively. These data suggested that the toxicity of ILs increased with the increase of side alkyl chain length, while anions had little influences on their toxicity to this alga. Moreover, changes in chlorophyll a content and chlorophyll fluorescence parameters (Fv/Fm and ΦPSII) indicated that the five ILs could damage the photosynthetic system of this alga resulting in the decrease of photosynthetic efficiency. The increased soluble protein content and antioxidase activity could be considered as an active response mechanism of this alga against the exposure of ILs. Content of malondialdehyde (MDA) in this alga increased significantly when it was exposed to ILs, suggesting that reactive oxygen species (ROS) were accumulated in the algal cells, which would cause injury of the algal biofilm and chloroplast. Therefore, results obtained in this work would help to explain the possible underlying toxic mechanisms of ILs to C. pyrenoidosa, and provide a significant theoretical support for assessing the toxicity of ILs to aquatic organisms.

Efficiency of Green Algae Chlorella vulgaris in Remediation of Polycyclic Aromatic Hydrocarbon (Anthracene) from Culture Media

The fresh water green alga Chlorella vulgaris was selected to study its ability to degrade one of polycyclic aromatic hydrocarbon (PAHs)known is anthracene (ANT). ANT is widely used in artificial products such as wood preservatives; insecticides; dye and coating materials. This algae was cultivated in CH-10 medium under constant laboratory conditions and exposed to different concentrations (1, 3, and 5 mg/l) of anthracene for 3, 5, 7, 9 and 15 days, with the concentration of ANT measured by high performance liquid chromatographic analysis (HPLC). The results showed that C.vulgaris has high ability to reduce anthracene to 80% at 1mg/Lcon centration after 3 days and 100% after 5 days, while at 3 and 5 mg / L concentration, the highest percentages were 89% and 99%, respectively after 9 days, with the complete removal (100%) was achieved after 15 days. The results indicate that this alga(C. vulgaris) has high ability for remediation of ANT and yield not toxic compound to environment

Application of alga-activated sludge combined system (AASCS) as a novel treatment to remove cephalosporins

Abstract The present research applied an alga-activated sludge combined system as a novel treatment to remove cephalosporins. First of all, the removal efficiency and characteristic of the common freshwater green alga Chlorella pyrenoidosa on cephalosporins were evaluated. The total removal rates for cefradine, cefalexin, ceftazidime and cefixime arrived up to 89.9%, 94.9%, 89.7% and 100%, respectively. On the other hand, the green alga had a satisfactory growth ability with the enlarged algal cell size during the whole treatment process. Finally, the removal efficiency of the alga-activated sludge combined system was evaluated. Due to the impact of the antibiotic, the removal rate of the individual activated sludge treatment was lower than 23.0%. 46.3% of the antibiotic were removed by the acclimated activated sludge after a two-week adaptation. However, a high total removal rate (97.91%) was obtained based on the combined system. It indicated that the green alga performed an excellent removal capacity for cefradine in the first treatment process. The activation of the alga also improved the removal efficiency of the subsequent activated sludge treatment process without acclimation. Compared with the traditional biological treatment, the combined treatment system could use the un-acclimated activated sludge directly and finally obtain high removal efficiency.

Resolution of Lipid Content from Algal Growth in Carbon Sequestration Studies

Green microalgae species was collected from Bhavani Lake of Erode in Erode District, Tamilnadu State, India. The Morphological studies were examined by utilizing Fourier Transform Infrared Spectroscopy, Microscope studies, Scanning Electron Microscopic studies and isolated and identified by PCR studies and by these studies that the collected specimen is to be Chlorella sp. In this study to check growth behavior and tolerance of fresh water green algae chlorella sp, under different pH,Temperature ,different concentrations of sodium bicarbonate salt, carbon dioxide gas and under different levels of sodium chloride salt.. From the study it is clear that optimum levels of proper carbon source and salinity is very much essential for growing Chorella sp., as they influences its growth rate, biomass and lipid productivity. The experiment aims to analyze the biomass productivity and total lipid content of the microalgae strain under various growth conditions. All the cultures were grown for a period of 10 days. For the growth study reveals that, pH range 4-7, Temperature 26-40, sodium bicarbonate salt concentrations 50-60 mg/l, sodium chloride concentration 0.02, maximum growth rate was observed, when CO2 gas was supplied at 40% concentration, maximum growth and maximum lipid yield of 15 in %dry cell weight were recorded. A highest total lipid content of 20 % was obtained.

An efficient and scalable extraction and quantification method for algal derived biofuel

Microalgae are capable of synthesizing a multitude of compounds including biofuel precursors and other high value products such as omega-3-fatty acids. However, accurate analysis of the specific compounds produced by microalgae is important since slight variations in saturation and carbon chain length can affect the quality, and thus the value, of the end product. We present a method that allows for fast and reliable extraction of lipids and similar compounds from a range of algae, followed by their characterization using gas chromatographic analysis with a focus on biodiesel-relevant compounds. This method determines which range of biologically synthesized compounds is likely responsible for each fatty acid methyl ester (FAME) produced; information that is fundamental for identifying preferred microalgae candidates as a biodiesel source. Traditional methods of analyzing these precursor molecules are time intensive and prone to high degrees of variation between species and experimental conditions. Here we detail a new method which uses microwave energy as a reliable, single-step cell disruption technique to extract lipids from live cultures of microalgae. After extractable lipid characterization (including lipid type (free fatty acids, mono-, di- or tri-acylglycerides) and carbon chain length determination) by GC–FID, the same lipid extracts are transesterified into FAMEs and directly compared to total biodiesel potential by GC–MS. This approach provides insight into the fraction of total FAMEs derived from extractable lipids compared to FAMEs derived from the residual fraction (i.e. membrane bound phospholipids, sterols, etc.). This approach can also indicate which extractable lipid compound, based on chain length and relative abundance, is responsible for each FAME. This method was tested on three species of microalgae; the marine diatom Phaeodactylum tricornutum, the model Chlorophyte Chlamydomonas reinhardtii, and the freshwater green alga Chlorella vulgaris. The method is shown to be robust, highly reproducible, and fast, allowing for multiple samples to be analyzed throughout the time course of culturing, thus providing time-resolved information regarding lipid quantity and quality. Total time from harvesting to obtaining analytical results is less than 2h.

EFFECT OF TEMPERATURE ON THE ACTIVITY OF ACID PHOSPHATASES ISOLATED FROM CHLORELLA FUSCA, CLADOPHORA GLOMERATA AND PHORMIDIUM FAVEOLARUM AND THERMAL STABILITY OF THE ENZYMES

Temperature effect has been investigated in this study on the phosphatases isolated from three algae representing different groups; a unicellular freshwater green alga Chlorella fusca, a filamentous green macroalga Cladophora glomerata and a filamentous freshwater blue green microalga, Phormidium faveolorum. The temperature dependence of the enzyme activity could be summarized as that 60 oC was the optimum temperature for the enzyme activity in Cladophora glomerata as well as Chlorella fusca whereas Phormidium faveolorum had an optimum temperature of 70 oC for both isolated enzyme fractions, the cell wall-bound and the secreted extracellular. The thermal behavior of the phosphatases isolated from the tested algae showed toleration to the thermal activation when p-nitrophenyl phosphate (pNPP) was utilized as a substrate which has been investigated to be itself is not sensitive to high temperatures. The two fractions of the enzyme isolated from the algae exhibited high stability at high temperatures even above 80 oC

Copper and zinc tolerance of two tropical microalgae after copper acclimation

Current toxicity tests with microalgae are often criticized as being overly sensitive to metals because algae are cultured in metal-deficient media. If such bioassays overestimate copper toxicity in surface waters, the relevance of water quality guidelines derived from these tests is questionable. In this study, the effect of acclimation to copper at environmentally relevant concentrations, on the sensitivity of the marine diatom Nitzschia closterium and the freshwater green alga Chlorella sp. to copper and zinc was examined. N. closterium was acclimated in culture medium containing 5 or 25 microg Cu L(-1) for 200 days, while Chlorella sp. was acclimated in medium containing 2 microg Cu L(-1) for 100 days. Changes in algal growth rates and copper and zinc tolerance were monitored using standard growth inhibition toxicity tests in minimal medium over 72 h. Neither of the two acclimated N. closterium cultures had increased zinc or copper tolerance compared with that of the nonacclimated algae, nor were there any changes in control growth rates. Similarly, no changes in copper tolerance or control growth rates were observed for the acclimated Chlorella sp. culture. This was supported by measurements of intracellular and extracellular copper which confirmed that there were no differences in copper accumulation in either acclimated or nonacclimated algae. These results suggest that these algae grown in standard culture media are generally no more sensitive than algae grown in a metal-enriched medium. This supports the continued use of current laboratory bioassays with microalgae, as part of a suite of tests for assessing metal bioavailability, for use in ecological risk assessments and for providing data for the derivation of water quality guidelines.

Growth Response and Heat Shock Protein (Hsp) Expression in Chlorella vulgaris Exposure to Elevated Temperatures

The present paper deals with the impact of various sublethal levels of temperature (26, 31, 33, 36, 39, 42 and 45o C) on growth and heat shock protein (Hsp) expression in freshwater green alga Chlorella vulgaris. Impact of select 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 a period of 15 days. To determine the induction of Hsp in the alga, it was exposed to select temperature levels for 3 hrs. and further kept for 6 hrs at culturing conditions at 26o C. Induction of Hsp was confirmed by immuno detection followed by SDSPolyacrylamide gel electrophoresis. The select growth parameters of the alga were reduced drastically at 39, 42 &amp; 45o C. Temperatures below 39o C may be considered as the limit of safe exposure for thermal stress of the alga. The Hsp 70 expression was also observed only at 39o C.

Inhibition of the water splitting system by sodium chloride stress in the green alga Chlorella vulgari

The effect of sodium chloride on the photosynthetic electron transport chain was investigated in the freshwater green alga Chlorella vulgaris. It was found that the rate of oxygen evolution under steady state and flash light conditions diminished by increasing salt concentrations. Salt treatment of cells also decreased the fluorescence and delayed luminescence yields. However, the fluorescence yield was almost completely restored by the addition of an artificial electron donor to the NaCl-treated cells. The oscillation pattern of the thermoluminescence B band as a function of flash number indicated that the S2&lt;FONT FACE=Symbol&gt;®&lt;/FONT&gt;S3 transition of the water splitting system is inhibited by NaCl treatment.

The effect of culture medium on metal toxicity to the marine diatom Nitzschia closterium and the freshwater green alga Chlorella pyrenoidosa

The composition of the culture medium and its effects on the toxicity of ionic copper and zinc to the marine diatom Nitszchia closterium and the toxicity of copper and lead to the freshwater green alga Chlorella pyrenoidosa were examined. The inhibitory concentration of copper giving 50% reduction in cell division rate in C. pyrenoidosa increased from 16 μg Cu l −1 in synthetic softwater and 24 μg Cu l −1 in EPA-AAP medium (minus EDTA) to >200 μg Cu l −1 in high nutrient MBL medium. Similarly, marine medium f reduced copper and zinc toxicity to N. closterium 10–20 fold compared to seawater. To overcome the problems of metal complexation by chelators such as silicate, iron and EDTA in the assay medium, unsupplemented seawater and buffered synthetic softwater, enriched only with nitrate and phosphate, have been used for the study of metal toxicities to marine and freshwater algae. These low nutrient media are sufficient to support algal growth over the 4-day assay period.

Comparison of physicochemical speciation procedures with metal toxicity to chlorella pyrenoidosa

Metal speciation as measured by anodic stripping voltammetry (ASV), adsorption on a resin with adsorbed hydrated aluminium oxide, and dialysis with receiving resins is compared with the toxicity of the metals to the freshwater green alga Chlorella pyrenoidosa Chick. In the presence of natural and synthetic ligands, similar labile fractions of metals were obtained for ASV at three electrodes (hanging mercury drop electrode, mercury film electrode and Nafion-coated mercury film electrode). The toxic fractions determined by ASV and bioassay were in reasonable agreement for zinc, cadmium and copper, and alteration of the analytical conditions provided some measure of agreement for lead. The resin with adsorbed hydrated aluminium oxide correlated well with bioassay for copper, but over-estimated lead toxicity and under-estimated cadmium toxicity. Dialysis with receiving resins under-estimated metal bioaccumulation in the presence of ligands. Metal speciation analysis for water samples gave higher toxic fractions for metals in samples of polluted river water and road runoff samples than those found in pristine river water.

Identification of wax esters of the fresh-water green alga chlorella kessleri by gas chromatography-mass spectrometry

Wax esters were detected in the fresh-water green alga Chlorella kessleri cultivated heterotrophically and their individual molecular classes of up to 50 carbon atoms were identified by means of capillary gas chromatography-mass spectrometry. The wax esters are composed from very long-chain fatty acids up to dotriacontanoic acid and alcohols up to 13-eicosenol with hexadecanol as a major representative. Monoenic acids have an unusual position of the double bond, namely at the n-18 position.

Composition of the nucleic acids of some algae.

AS part of a study on the chemical composition of algae1, the composition of the nucleic acids of various algae was investigated in order to determine whether there were differences between different groups of marine and freshwater forms. The following algae were studied : the freshwater diatoms Navicula pelliculosa (Breb.) Hilse and Nitzschia palea (Kutz.) W. Sm. ; the marine diatom Cylindrotheca gracilis (Breb.) Grun. ; the freshwater blue-green alga Anacystis nidulans (Richt.) Dr. and Daily ; and the freshwater green alga Chlorella pyrenoidosa Chick.