Strains Of Green Microalgae Research Articles

Starch-based flocculant outperformed aluminium sulfate hydrate and polyaluminium chloride through effective bridging for harvesting acicular microalga Ankistrodesmus

Microalgae represent a diversified pool of resources famed for valuable raw materials which are favoured over terrestrial crops in certain applications. Even so, limited green microalgae strains have been explored and studied till date. Thus, the highlight of this study is to comparatively evaluate the performance of pH-induced settling, use of chemical coagulants and starches as natural coagulants for efficient harvesting of acicular-shaped Ankistrodesmus. Biomass recoveries were determined through conventional jar tests and small scale coagulation-flocculation studies. Increased acidity at pH3 and enhanced basicity above pH11.5 have facilitated self-flocculation of cells leading to rapid settling. Despite that, potential reduction in chlorophyll contents and contamination from resulting precipitation of hydroxides evident from field-emission scanning electron microscopy micrographs may limit further applications of harvested biomass. By adding 12mg/L of alum or 4.8mg/L of polyaluminium chloride, up to 36.6% and 40% of the initial biomass was harvested respectively at pH6. Their poor performances were deduced to be the effect of buoyancy due to the long, curved needle-like structure with tapered ends of Ankistrodesmus. Remarkably, the use of 120mg/L of autoclaved rice starch has enhanced the biomass recovery to at least 80%; improvement of 2 fold from those achieved using chemical coagulants. The bridging mechanism induced by the use of starches coupled with the effect of slow mixing has been found to be paramount for enhancing the floc formation process through effective linking of neighbouring cells. Subsequently, an extended blanket of Ankistrodesmus cells was formed which facilitated its heightened settling upon treatment with starches.

Testing of two different strains of green microalgae for Cu and Ni removal from aqueous media

The concentration of metal ions in aqueous media is a major environmental problem due to their persistence and non-biodegradability that poses hazards to the ecosystem and human health. In this study, the effect of Cu and Ni on the growth of two green microalgal strains, Chlorella vulgaris and Desmodesmus sp., was evaluated along with the removal capacity from single metal solutions (12days exposure; metal concentration range: 1.9–11.9mgL−1). Microalgal growth showed to decrease at increasing metal concentrations, but promising metal removal efficiencies were recorded: up to 43% and 39% for Cu by Desmodesmus sp. and C. vulgaris, respectively, with a sorption capacity of 33.4mggDW−1 for Desmodesmus sp. As for Ni, at the concentration of 5.7mgL−1, the removal efficiency reached 32% for C. vulgaris and 39% for Desmodesmus sp. In addition, Desmodesmus sp. growth and metal removal were evaluated employing bimetallic solutions. In these tests, the removal efficiency for Cu was higher than that of Ni for all the mix solutions tested with a maximum of 95%, while Ni-removal reached 90% only for the lowest concentrations tested. Results revealed that the biosorption of both metals reached maximum removal levels within the fourth day of incubation (with metal uptakes of 67mgCugDW−1 and 37mgNigDW−1). Intracellular bioaccumulation of metals in Desmodesmus sp. was evaluated by confocal laser scanning microscopy after DAPI staining of cells exposed or not to Cu during their growth. Imaging suggested that Cu is sequestered in polyphosphate bodies within the cells, as observable also in phosphorus deprived cultures. Our results indicate the potential of employing green microalgae for bioremediation of metal-polluted waters, due to their ability to grow in the presence of high metal concentrations and to remove them efficiently.

DNA Barcoding Green Microalgae Isolated from Neotropical Inland Waters.

This study evaluated the feasibility of using the Ribulose Bisphosphate Carboxylase Large subunit gene (rbcL) and the Internal Transcribed Spacers 1 and 2 of the nuclear rDNA (nuITS1 and nuITS2) markers for identifying a very diverse, albeit poorly known group, of green microalgae from neotropical inland waters. Fifty-one freshwater green microalgae strains isolated from Brazil, the largest biodiversity reservoir in the neotropics, were submitted to DNA barcoding. Currently available universal primers for ITS1-5.8S-ITS2 region amplification were sufficient to successfully amplify and sequence 47 (92%) of the samples. On the other hand, new sets of primers had to be designed for rbcL, which allowed 96% of the samples to be sequenced. Thirty-five percent of the strains could be unambiguously identified to the species level based either on nuITS1 or nuITS2 sequences’ using barcode gap calculations. nuITS2 Compensatory Base Change (CBC) and ITS1-5.8S-ITS2 region phylogenetic analysis, together with morphological inspection, confirmed the identification accuracy. In contrast, only 6% of the strains could be assigned to the correct species based solely on rbcL sequences. In conclusion, the data presented here indicates that either nuITS1 or nuITS2 are useful markers for DNA barcoding of freshwater green microalgae, with advantage for nuITS2 due to the larger availability of analytical tools and reference barcodes deposited at databases for this marker.

Evaluation of Various Extraction Techniques for Efficient Lipid Recovery from Thermo-Resistant Microalgae, <i>Hindakia</i>, <i>Scenedesmus</i> and <i>Micractinium</i> Species<br/>—Comparison of Lipid Extraction Methods from Microalgae

In recent years, photosynthetic microalgae regained attention for biodiesel production. For efficient utilization of microalgae, a number of criteria including a strain with high biomass and lipid productivities and employment of effective and reliable methods for oil extraction from the obtained biomass should be met. Recently, we have isolated and identified three thermo-resistant green microalgae strains, namely; Scenedesmus sp. ME02, Hindakia tetrachotoma ME03 and Mic-ractinium sp. ME05. In this study, we compared percent lipid content of thermos-tolerant mic-roalgal strains using the following solvent extraction methods: Soxhlet, Bligh and Dyer and Folch methods with or without assisted cell disruption techniques including lyophilization, homogenization, ultrasonication, bead and microwave-assisted. The highest increase in lipid yield was obtained with a combination of lyophilization and ultrasonication techniques together with Soxhlet method: 27% of total dry weight for Micractinium sp. ME05. We conclude that lyophilization and ultrasonication are effective assistance methods for lipid extraction from thermo-resistant microalgae.

Screening for hydrogen-producing strains of green microalgae in phosphorus or sulphur deprived medium under nitrogen limitation

Hydrogen gas, one of the best candidates for clean and renewable energy, can be produced by microalgae that can use solar energy to cause photolysis of water. This study screened H-2-producing indigenous green microalgae under sulphur (S-) deprivation, simultaneous nitrogen (N-) limitation and S-deprivation, or simultaneous N-limitation and phosphorus (P-) deprivation. Sequences of 18S rDNA and ITS in conjunction with morphological characteristics were used to identify the algae. We report that Chlorella lewinii, Micractinium sp., Coelastrella sp., and Monoraphidium sp. have the ability to produce H-2. The increase in H-2 photoproduction when N is limited seems to be a universal phenomenon in most tested strains of Chlorella, in all strains of Chlamydomonas, but in no strain of Coelastrella, Micractinium, or Scenedesmus. Chlorella sorokiniana KU204 produced H-2 (46 ml/l) under S-deprivation. This strain exhibited the highest H-2-producing ability (1.30 ml l(-1) h(-1)) and accumulated up to 90 ml/l under simultaneous N-limitation and S-deprivation. Interestingly, C. sorokiniana KU204 could also produce H-2 under simultaneous N-limitation and P-starvation (69 ml/l). The induction time to reach an anoxic state by most tested strains of Chlorella, but not Chlamydomonas, was shorter under simultaneous N-limitation and S-deprivation than under S-deprivation. In addition, those strains of Chlorella exhibited high H-2 photoproduction under simultaneous N-limitation and S-deprivation. A few Chlorella strains were unable to reach an anoxic state during the experiment. However, such regularity is not found in Chlamydomonas. The results indicate that the mechanism of H-2 photoproduction in Chlorella may differ from that in Chlamydomonas.

Improvement of carbon dioxide removal through artificial light intensity and temperature by constructed green microalgae consortium in a vertical bubble column photobioreactor

Aims: This study was aimed to demonstrate that environmental conditions, such as light intensity, photoperiodism and temperature, played a determining role in improving CO2 removal and cellular propagation. Photosynthesis by microalgae in a direct CO2 to biomass conversion in engineered systems such as photobioreactors, has been frequently used for CO2 removal. The goal of this study was to obtain high CO2 removal by green microalgae strains cultivated in a vertical bubble column photobioreactor. Methodology and results: Constructed consortium containing Chlorella sp., Scenedesmus obliquus, and Ankistrodesmus sp. were cultured in temperatures (°C) of 25, 30, 25; light intensities (lux) of 2500, 4000 and photoperiodisms (light/dark; hour) of 24/0, 16/8, and 12/12. The experiment demonstrated that microalgae was capable of tolerating up to 7% CO2 concentrations under variation of light intensities, photoperiodisms, and temperature conditions. Synergetic of three microalgae capable of utilizing CO2 and transformed it to become biomass. The result also showed that growth was best at light intensity of 4000 lux for 16 h a day and temperature of 30 °C. The maximum growth rate (µ) of 0.38 per day was obtained from culture injected with 5% CO2 concentration. Conclusion, significance and impact study: The CO2 removal efficiency (%) was 49.02, whereas CO2 utilization efficiency (%), carbon dioxide transfer rate (CTR; gCO2/L.h) and carbon dioxide fixation rate (qCO2/h) were 15.15, 101.29 and 42.02, respectively. Biofixation of CO2 by the constructed consortium has recently gained renewed interest as a promising strategy for CO2 mitigation.

Biosorption of trace metals from aqueous multimetal solutions by green microalgae

Two strains of green microalgae C. reinhardti and C. pyrenoidosa were examined for their biosorption of Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, and Cd2+ from aqueous multi-metal solutions. A wide range of biosorption capacities can be observed due to different strains of microalgae and different species of trace metals. This characteristic was ascribed to the distinct components and structures of algal cell walls and the different physicochemical properties of trace metals, such as atomic weight and ion density. C. pyrenoidosa showed higher uptake capacities than C. reinhardti and both of them had a preference for the uptake of cadmium over others in the trace metal solution, suggesting they can be a good biomaterial for biosorption of cadmium. Live microalgal cells displayed a more complex sorption process than dead microalgal cells because of cell assimilation.

Evaluation of antioxidant capacities of green microalgae

Three strains of green microalgae, Chlorococcum sp.C53, Chlorella sp. E53, and Chlorella sp.ED53 were studied for their antioxidant activities. Crude extracts of these microalgae in hot water and in ethanol were examined for their total phenolic contents and for their antioxidant capacities. In order to determine their phenolic contents, the Folin–Ciocalteu method was used. As for the determination of their antioxidant capacities, four different assays were used: (1) total antioxidant capacity determination; (2) DPPH radical scavenging assay; (3) ferrous ion chelating ability assay; and (4) inhibition of lipid peroxidation (using thiobarbituric acid reactive substance). For all the strains we have studied, their ethanolic extract showed more antioxidant activities than their hot water extract. Categorically, the ethanolic extract of Chlorella sp.E53 exhibited both the highest total phenolic content of 35.5 ± 0.14 mg gallic acid equivalent (GAE) g−1 dry weight and the highest DPPH radical scavenging of 68.18 ± 0.38 % at 1.4 mg mL−1 (IC50 0.81 mg mL−1), whereas Chlorella sp.ED53 showed both the highest ferrous ion chelation activity of 42.78 ± 1.48 % at 1 mg mL−1 (IC50 1.23 mg mL−1) and the highest inhibition of lipid peroxidation of 87.96 ± 0.59 % at 4 mg mL−1. This high level of inhibition is comparable to 94.42 ± 1.39 % of butylated hydroxytoluene, a commercial synthetic antioxidant, at the same concentration.

Study of hydrogen production by three strains of Chlorella isolated from the soil in the Algerian Sahara

In this study, the photosynthetic hydrogen production rates by some strains of green microalgae were investigated. Three strains of Chlorella isolated from and soil and foggaras's water in the Algerian Sahara were used. Chlorella sorokiniana strain Ce, Chlorella salina strain Mt and Chlorella sp strain Pt6 produced hydrogen gas under sulphur-deprived conditions, but its rate was dependent on strain type and oxygen partial pressure in medium. In C. sorokiniana strain Ce, the maximum value of hydrogen accumulated was 147 ml at 222 h at 2% of O-2 pressure. Compared to C. sorokiniana strain Ce, C. salina strain Mt and Chlorella sp strain Pt6 produced less amount of hydrogen, but they were able to sustain with an O-2 partial pressure of up to 11-15.4%. Our data were compared with hydrogen production by Chlamydomonas reinhardtii. In this communication, the relationship between physiological behaviour, biochemical characteristic (starch and protein) and rates gas production (O-2 and H-2) was also specified. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.

Adhesion of façade coating colonisers, as mediated by physico-chemical properties

The adhesion of Klebsormidium flaccidum, Stichococcus bacillaris and Chlorella cf. mirabilis, three strains of green microalgae isolated from biofilms on façade coatings were investigated in a parallel plate flow chamber. The model surfaces tested were glass slides, and −CH3 (mediated by octadecyltrichlorosilane [OTS] and hexamethyldisilazane [HMDZ] modification) and -NH2 (aminopropyltriethoxysilane [APS] modification) terminated self-assembled monolayers. Algal physicochemical properties were evaluated by the microbial adhesion to solvents (MATS) assay and by contact angle measurements. The model surfaces were characterised by X-ray photoelectron spectroscopy analysis and by contact angle measurements. Predicted adhesion trends were then compared to in vitro measurements. The adhesion strength of the three algal strains followed the trend: APS > OTS > HMDZ > glass. The adhesion process thus seemed to be mediated by hydrophobic and electrostatic interactions, and was shown to be influenced by the algal culture age and the initial contact time.

Activity of blue green microalgae extracts against in vitro generated Staphylococcus aureus with reduced susceptibility to vancomycin

Blue green microalgae have been identified as one of the promising groups of organism from which biochemically active natural products have been isolated. Aqueous and organic extracts of nine blue green microalgae strains were screened against in vitro generated vancomycin intermediate resistant Staphylococcus aureus (VISA) strains. Aqueous extracts of all the blue green microalgae cultures were found to be inactive, while all the organic (hexane, chloroform and methanolic) extracts of Anabaena virabilis and Anabaena sp. showed activity against VISA strains with MIC of 32–64 μg/ml.

Effects of sublethal concentrations of copper on three strains of green microalgae under autotrophic and mixotrophic culture conditions

The effects of sublethal copper concentrations were assayed on Chlorella kess- leri, Coelastrum sphaericum and Scenedesmus acutus in autotrophic and mixotrophic media. The strains showed different susceptibility to copper in the bioassay, being C. sphaericum more resistant to metal exposure. Bleaching and lipid peroxidation were more pronounced in absence of organic carbon in C. kessleri and S. acutus, but remained unaffected in C. sphaericum. Acetate addition diminished free copper cation concentra- tion in growth media, increased growth rate in all cases and attenuated metal effect on bleaching and lipid peroxidation in C. kessleri and S. acutus. In C. sphaericum, the dele- terious effect on growth rate observed with the highest copper concentration might be due to copper-altered acetate assimilation.