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Carbon dioxide (CO2) sequestration by microalgae has received widespread attention. Growth and biomass quality using flue gas, combined with medium recycling, were evaluated in this study. Results indicated that Spirulina maxima FACHB 438 can use flue gas from biomass power plant as sole carbon source. The final biomass of 26.30, 22.10, and 23.95 g in fresh medium (FM), recycled medium (RM), and recycled medium with activated carbon treatment (RM + AC) was harvested in flat-plate photobioreactors with 10 L working volume after 5 cycles, respectively. The mean specific growth rate and CO2 fixation rate did not differ significantly (p

Haematococcus pluvialis is beneficial to human health and is important for commercial use. However, it seldom prevails in permanent freshwater bodies. Increasing environmental pollutants from anthropogenic activity may threaten the wide distribution of H. pluvialis. Here, we quantified and compared the adverse effects of the common pesticides atrazine, pentachlorophenol, malathion, and 3,5-dichlorophenol and the heavy metals Cu(II), Cr(VI), and Cd(II) on H. pluvialis, Microcystis wesenbergii (a freshwater bloom-forming cyanobacterium), and Pseudokirchneriella subcapitata (a standard toxicity test species). We found that H. pluvialis was the species most sensitive to 3,5-dichlorophenol and Cr(VI) exposure and the most tolerant to pentachlorophenol exposure according to IC50, changes in chlorophyll a content, maximum electron transport rates (ETRmax), the quantum efficiency of photosystem II (Fv/Fm), and esterase activity. Haematococcus pluvialis was also the species most sensitive to atrazine according to IC50, chlorophyll a, and ETRmax. Overall, our findings suggest that atrazine, 3,5-dichlorophenol, and Cr(VI) are potential factors limiting the distribution of H. pluvialis. We suggest that H. pluvialis can be a potentially useful bioindicator for evaluating pollutants. Furthermore, ETRmax, FDA assay, and flow cytometry can be combined with Haematococcus to test for toxicity.

The cyanobacterium Pseudanabaena sp. FACHB 1277, a 2-methylisoborneol (2-MIB) producer isolated from Xionghe Reservoir, was identified by molecular biological methods based on the 16S rDNA sequence. Pseudanabaena sp. FACHB 1277 is a planktonic freshwater species with relatively high 2-MIB per cell density value (7.76 × 10−6 ng cell−1) and specific growth rate (0.25 ± 0.01 d−1). The effects of temperature and light intensity on 2-MIB production of Pseudanabaena sp. FACHB 1277 were investigated. Of the six temperatures tested, 10, 15, 20, 25, 30, and 35 °C, the maximum total 2-MIB per cell density and minimum cell density were observed at 10 °C, while the total 2-MIB and dissolved 2-MIB (including extracellular and dissolved intracellular 2-MIB) increased with increasing temperature. Among the six tested light intensities (10, 25, 40, 55, 70, and 85 μmol photons m−2 s−1), the minimum total 2-MIB per cell density and maximum cell density were observed at 25 μmol photons m−2 s−1. The total 2-MIB and extracellular 2-MIB increased with light intensity increasing from 10 to 40 μmol photons m−2 s−1, while no significant increase was observed when the light intensity was higher than 40 μmol photons m−2 s−1. The maximum intracellular 2-MIB (including dissolved and bound) occurred at 25 μmol photons m−2 s−1. The present study indicates that increasing temperature could favor the conversion of bound intracellular to dissolved 2-MIB, while increasing light intensity stimulates the release of dissolved intracellular 2-MIB into the environment.

The cyanobacterium Nostoc sphaeroides Kutzing is expected to be effective in toxic metal adsorption as it produces abundant exopolysaccharides with functional groups. Therefore, the adsorption properties of Cu2+, Cd2+, Cr3+, Pb2+, Ni2+, and Mn2+ on fresh macrocolonies and algal powder of N. sphaeroides were compared at pH 5 and 25 °C. The adsorption capacity of fresh biomass for Pb2+ and of algal powder for Pb2+ and Cr3+ were highest in single metal solutions. Compared to the fresh biomass, the metal adsorption capacities of algal powder were similar for Ni2+, Cd2+, and Pb2+ and slightly greater for Cr3+, but they were markedly smaller for Mn2+ and Cu2+. Coexisting ions (in tap water or in multiple solutions) significantly decreased the metal adsorption capacity, except for Cr3+ in tap water. The Pb2+ and Cr3+ adsorption dynamic process fitted the pseudo-second-order model well, showing fast adsorption at the first stage in 10 and 20 min, respectively. Higher pH in acidic ranges favored the adsorption greatly. The Langmuir isotherm model was suitable for explaining the adsorption, and the maximum adsorption capacities were 116.28 and 22.37 mg g−1 for Pb2+ and Cr3+, respectively. The adsorption process was endothermic, confirmed by the significantly higher adsorption capability at higher temperature. Hydroxyl, amino, and carboxyl groups were the main functional groups based on Fourier transform infrared spectroscopy analysis, and they bind to metal ions via ion exchange. The results suggest that fresh macrocolonies of N. sphaeroides can be used as an effective biosorbent for metal ion removal, especially for Pb2+ and Cr3+.

Bioflocculants of Chlamydomonas reinhardtii were investigated under axenic conditions. C. reinhardtii was found to produce significant amounts of bioflocculants. Flocculating activity by C. reinhardtii began in the linear phase of growth and continued until the end of the stationary phase. The highest flocculating efficiency of the culture broth was 97.06%. The purified C. reinhardtii bioflocculant was composed of 42.1% (w/w) proteins, 48.3% carbohydrates, 8.7% lipids, and 0.01% nucleic acid. The optimum condition for bioflocculant production of C. reinhardtii was as follows: under temperature of 15A degrees C to 25A degrees C, pH 6-10 and illumination of 40-60 mu mol photons m(-2) s(-1). The bioflocculants produced by C. reinhardtii showed maximum activity in pH ranges from 2 to 10. The flocculating activity was significantly enhanced by the addition of CaCl2 as a co-flocculant at an optimal concentration of 4.5 mM.

Arsenic pollution and eutrophication are both prominent issues in the aquaculture ponds of Taiwan. It is important to study the effects of arsenic on algal growth and toxin production in order to assess the ecological risk of arsenic pollution, or at least to understand naturally occurring ponds. The sensitivity of algae to arsenate has often been linked to the structural similarities between arsenate and phosphate. Thus, in this study we examined the effects of arsenate (10(-8) to 10(-4) M) on Microcystis aeruginosa TY-1 isolated from Taiwan, under two phosphate regimes. The present study showed that M. aeruginosa TY-1 was arsenate tolerant up to 10(-4) M, and that this tolerance was not affected by extracellular phosphate. However, it seems that extracellular phosphate contributed to microcystin production and leakage by M. aeruginosa in response to arsenate. Under normal phosphate conditions, total toxin yields after arsenate treatment followed a typical inverted U-shape hormesis, with a peak value of 2.25 +/- 0.06 mg L-1 in the presence of 10(-7) M arsenate, whereas 10(-8) to 10(-6) M arsenate increased leakage of similar to 75% microcystin. Under phosphate starvation, total toxin yields were not affected by arsenate, while 10(-6) and 10(-5) M arsenate stimulated microcystin leakage. It is suggested that arsenate may play a role in the process of microcystin biosynthesis and excretion. Given the arsenic concentrations in aquaculture ponds in Taiwan, arsenate favors survival of toxic M. aeruginosa in such ponds, and arsenate-stimulated microcystin production and leakage may have an impact on the food chain.

The effects of temperature and light on the growth and geosmin production of Lyngbya kuetzingii were determined. Of the three temperatures tested, 10, 25 and 35A degrees C, the maximal geosmin concentration and geosmin productivity were yielded at 10A degrees C, while the highest chl a production was observed at 25A degrees C. In the studies on light intensity, the maximal geosmin concentration and geosmin productivity were observed at 10 mu mol m(-2) s(-1), while the highest chl a production was at 20 mu mol m(-2) s(-1). It was suggested that more geosmin was synthesized with lower chl a demand. Meanwhile, the relative amounts of extra- and intracellular geosmin were investigated. Under optimum growth conditions (20 mu mol m(-2) s(-1), 25A degrees C; BG-11 medium), the amounts of extracellular geosmin increased as the growth progressed and reached the maximum in the stationary phase, while the intracellular geosmin reached its maximum value in the late exponential phase, and then began to decline. However, under the low temperature (10A degrees C) or light (10 mu mol m(-2) s(-1)) conditions, more intracellular geosmin was synthesized and mainly accumulated in the cells. The proportions of extracellular geosmin were high, to 33.33 and 32.27%, respectively, during the stationary phase at 35A degrees C and 20 mu mol m(-2) s(-1). It was indicated that low temperature or light could stimulate geosmin production and favor the accumulation of geosmin in cells, while more intracellular geosmin may be released into the medium at higher temperatures or optimum light intensity.

Four filamentous cyanobacteria, Microcoleus vaginatus, Phormidium tenue, Scytonema javanicum (Kutz.) and Nostoc sp., and a single-celled green alga, Desmococcus olivaceus, all isolated from Shapotou (Ningxia Hui Autonomous Region of China), were batch cultured and inoculated onto unconsolidated sand in greenhouse and field experiments. Their ability to reduce wind erosion in sands was quantified by using a wind tunnel laboratory. The major factors related to cohesion of algal crusts, such as biomass, species, species combinations, bioactivity, niche, growth phase of algae, moisture, thickness of the crusts, dust accretion (including dust content and manner of dust added) and other cryptogams (lichens, fungi and mosses) were studied. The best of the five species were M. vaginatus and P. tenue, while the best mix was a blend of 80% M. vaginatus and 5% each of P. tenue,S. javanicum,Nostoc sp. and D. olivaceus. The threshold friction velocity was significantly increased by the presence of all of the cyanobacterial species, while the threshold impact velocity was notably increased only by the filamentous species. Thick crusts were less easily eroded than thin crusts, while biomass was more effective than thickness. Dust was incorporated best into Microcoleus crust when added in small amounts over time, and appeared to increase growth of the cyanobacterium as well as strengthen the cohesion of the crust. Microbial crust cohesion was mainly attributed to algal aggregation, while lichens, fungi and mosses affected more the soil structure and physico-chemical properties.