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An alternative stress-inducing method, a low-energy pulsed electric field (LE-PEF), was used to improve the lipid productivity of microalgae cultures. A large shift in the Nile-Red-stained peaks toward a higher intensity in fluorescent-activated cell sorting, suggestive of an increased neutral lipid content, was observed when 10 kV LE-PEF pulses were applied to 800 mL batch cultures of Acutodesmus dimorphus. The optimal LE-PEF on-off cycle treatment for A. dimorphus was 2 s on-60 s off for 15 min with 6 cycles per day. Under these optimal LE-PEF treatment conditions, A. dimorphus showed an overall 28.8 % increase in lipid productivity. Therefore, based on these results, LE-PEF can be regarded as a promising tool to avoid the lipid content and growth rate trade-off and improve the lipid productivity of microalgae in various cultivation systems. [ABSTRACT FROM AUTHOR]

Abstract: Over 100 green-colored colonies were isolated from environmental samples when cultivating on a BG11 agar medium, and 4 strains showing different morphologies were selected based on light microscopic observation. Among these strains, the microalgal species with the highest growth rate under 10% CO2 was identified as Ettlia sp. YC001 using an 18S rDNA-based phylogenetic analysis and morphological comparison. The highest cell density of 3.10g/L (based on dry cell weight) and biomass productivity of 0.19g/L/d were obtained under 5% CO2 after 16days. The lipid content and productivity were also up to 42% of the dry cell weight and 80.0mg/L/d, respectively. The color of the Ettlia sp. YC001 culture changed from green to red after a month due to the accumulation of certain carotenoids. Therefore, it would seem that Ettlia sp. YC001 is appropriate for mitigating CO2 due to its high biomass productivity, and a suitable candidate for producing biodiesel and high-value products. [Copyright &y& Elsevier]

Spirulina platensis, a filamentous cyanobacterium, produces γ-linolenic acid (GLA, 18:3), which is an important anti-inflammatory for pharmaceutical use. Thus, to increase the GLA content in S. platensis, this study investigated the combined effect of a light-dark (LD) two-stage culture and mixotrophic culture including a precursor of GLA. When compared with a photoautotrophic culture, the supplement of a GLA precursor, such as a long- or short-chain carbon source, enhanced the total fatty acid and GLA contents in the cells in the two-stage culture. The highest GLA content of 2% ( w/ w) and productivity of 27.6 ± 4.7 mg L were obtained in S. platensis when using 0.01 mM palmitic acid as a supplement in the two-stage culture. This study also suggests that a mixotrophic and LD two-stage culture may represent a method for increasing the total lipid production, which can then be converted to biofuels. [ABSTRACT FROM AUTHOR]

Abstract: Cyanobacterial blooms in eutrophied water body are generally composed of various genotypes with or without microcystin-producing genes (mcy gene cluster). Thus there is a need for quantification of potent toxin producing strains. The present study aimed at identifying microcystin variants and its producer strains in Durgakund pond, Varanasi, India, based on quantification of cpcBA-IGS and mcyA (condensation domain) genes using real-time PCR and LC–MS. Increase in microcystin concentrations was correlated with increase in mcyA copy number and the level of pigments (chlorophyll a, phycocyanin and carotenoids). Also, selected environmental factors (water temperature, light irradiance, rainfall, pH, N and P) and the concentration of microcystin variants (MC-LR, -RR and -YR) were also assessed in samples during May 2010 to April 2011 to establish the possible correlation among these parameters. Nutrients favored cyanobacterial bloom but it could not be correlated with the levels of microcystin variants and seemed to be geographically specific. Microcystis sp. dominant in the pond comprised potentially toxigenic cells. The ratio of potentially toxigenic Microcystis sp. to that of total Microcystis sp. ranged from 0% to 14%. Such studies paved the way to identify and quantify the most potent microcystin producer in the tropical aquatic body. [Copyright &y& Elsevier]

The influence of nitrogen (N) deficiency on the cell growth and intracellular lipid production of the alga Botryococcus braunii UTEX 572 was investigated. Biomass concentration and lipid content of B. braunii cultivated in modified Chu-13 medium containing 0.04, 0.37, and 3.66 mM nitrate were 0.23-0.38 g L and 36-63% of dry cell weight, respectively. The specific growth rate of B. braunii reached a constant of 0.185 day during cultivation with an initial nitrate feed of 3.66 mM. The maximum lipid content of B. braunii was 63% with 0.04 mM nitrate. However, the maximum lipid productivity of 0.019 g L day was achieved with 0.37 mM nitrate. The level of oleic acid, an important component of biodiesel, was higher at 86% of the total fatty acids under N-limited conditions (0.04 mM nitrate) compared to 69% under N-sufficient conditions (3.66 mM nitrate). Furthermore, expression of the stearoyl-ACP desaturase gene ( sad) encoding a stearoyl-ACP desaturase involved in the synthesis of oleic acid was 2.6-fold higher under N-limited conditions than under N-sufficient conditions. [ABSTRACT FROM AUTHOR]

This study investigated the feasibility of using photoheterotrophic microalga, Desmodesmus armatus SCK, for removal of cesium (Cs+) followed by recovery process using magnetic nanoparticles. The comparison of three microalgae results indicated that D. armatus SCK removed the most Cs+ at both 25 °C and 10 °C. The results also revealed that the use of microalga grown in potassium (K+)-starved condition improves the accumulation of Cs+. Heterotrophic mode with addition of volatile fatty acids (VFAs), especially acetic acids (HAc), also enhanced removal of Cs+ by K+-starved D. armatus SCK; maximum removal efficiency of Cs+ was almost 2-fold higher than that of cells grown without organic carbon source. The Cs+ taken up by this microalga was efficiently harvested using magnetic nanoparticles, polydiallyldimethylammonium (PDDA)-FeO 3. Finally, this strain eliminated more than 99% of radioactive 137Cs from solutions of 10, 100, and 1000 Bq mL−1. Therefore, use of K+-starved microalga, D. armatus SCK, with VFAs could be promising means to remove the Cs from the liquid wastes. Image 1 • Microalga D. armatus can eliminate radioactive 137Cs, even at low concentrations. • Addition of VFA can significantly enhance removal capability of Cs+ by microalga. • Cs-containing microalgae are efficiently recovered using nano-magnetic FeO 3 -PDDA. • K+-starved microalga can improve removal efficiency of Cs+ at 25 °C and 10 °C. [ABSTRACT FROM AUTHOR]

A Gram-negative, aerobic, motile, and rod-shaped bacterial strain designated CR182T was isolated from freshwater of the Nakdong River, Republic of Korea. Optimal growth conditions for this novel strain were found to be: 25-30 °C, pH 6.5-8.5, and 3% (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequence indicates that the strain CR182T belongs to type strains of genus Paucibacter. Strain CR182T showed 98.0% 16S rRNA gene sequence similarity with Paucibacter oligotrophus CHU3T and formed a robust phylogenetic clade with this species. The average nucleotide identity value between strain CR182T and P. oligotrophus CHU3T was 78.4% and the genome-to-genome distance was 22.2% on average. The genomic DNA G+C content calculated from the genome sequence was 66.3 mol%. Predominant cellular fatty acids of strain CR182T were summed feature 3 (C16:1 ω7c and/or C16:1 ω6c) (31.2%) and C16:0 (16.0%). Its major respiratory quinine was ubiquinone Q-8. Its polar lipids consisted of diphosphatidylglycerol, phosphatidylethanolamine, and two unidentified phospholipids. Its genomic DNA G+C content was 66.3%. Based on data obtained from this polyphasic taxonomic study, strain CR182T represents a novel species belonging to genus Paucibacter, for which a name of P. aquatile sp. nov. is proposed. The type strain is CR182T (= KCCM 90284T = NBRC 113032T). [ABSTRACT FROM AUTHOR]

This work describes the development of a microalga-mediated process for simultaneous removal of residual ammonium nitrogen (NH 4 + -N) and production of lipids from biologically treated coke effluent. Four species of green algae were tested using a sequential mixotrophic process. In the first phase—CO 2 -supplied mixotrophic condition—all microalgae assimilated NH 4 + -N with no evident inhibition. In second phase—volatile fatty acids (VFAs)-supplied mixotrophic condition—removal rates of NH 4 + -N and biomass significantly increased. Among the microalgae used, Arctic Chlorella sp. ArM0029B had the highest rate of NH 4 + -N removal (0.97 mg/L/h) and fatty acid production (24.9 mg/L/d) which were 3.6- and 2.1-fold higher than those observed under the CO 2 -supplied mixotrophic condition. Redundancy analysis (RDA) indicated that acetate and butyrate were decisive factors for increasing NH 4 + -N removal and fatty acid production. These results demonstrate that microalgae can be used in a sequential process for treatment of residual nitrogen after initial treatment of activated sludge. [ABSTRACT FROM AUTHOR]

Mass cultivation of microalgae is necessary to achieve economically feasible production of microalgal biodiesel, but the high cost of nutrients is a major limitation. In this study, orange peel extract (OPE) was used as an inorganic and organic nutrient source for the cultivation of Chlorella vulgaris OW-01. Chemical composition analysis of the OPE indicated that it contains sufficient nutrients for mixotrophic cultivation of C. vulgaris OW-01. Analysis of biomass and FAME production showed that microalgae grown in OPE medium produced 3.4-times more biomass and 4.5-times more fatty acid methyl esters (FAMEs) than cells cultured in glucose-supplemented BG 11 medium (BG-G). These results suggest that growth of microalgae in an OPE-supplemented medium increases lipid production and that OPE has potential for use in the mass cultivation of microalgae. [ABSTRACT FROM AUTHOR]

We demonstrated a comprehensive approach for development of axenic cultures of microalgae from environmental samples. A combination of ultrasonication, fluorescence-activated cell sorting ( FACS), and micropicking was used to isolate axenic cultures of Chlorella vulgaris Beyerinck ( Beijerinck) and Chlorella sorokiniana Shihira & R.W. Krauss from swine wastewater, and Scenedesmus sp. YC001 from an open pond. Ultrasonication dispersed microorganisms attached to microalgae and reduced the bacterial population by 70%, and when followed by cell sorting yielded 99.5% pure microalgal strains. The strains were rendered axenic by the novel method of micropicking and were tested for purity in both solid and liquid media under different trophic states. Denaturing gradient gel electrophoresis ( DGGE) of 16S rRNA gene confirmed the absence of unculturable bacteria, whereas fluorescence microscopy and scanning electron microscopy ( SEM) further confirmed the axenicity. This is the most comprehensive approach developed to date for obtaining axenic microalgal strains without the use of antibiotics and repetitive subculturing. [ABSTRACT FROM AUTHOR]

Abstract: Increased cyanobacterial blooms, a source of cyanotoxins are linked with climate change and eutrophication in aquatic bodies, a major concern worldwide. Microcystins are potently hepatotoxic, nephrotoxic as well as carcinogenic. Thus microcystins are threat to tourism, agriculture and animal''s health. However, there is a still lacuna in the knowledge of regulation of microcystins production. Presence of toxic and non-toxic cyanobacterial strains together and occurrence of various microcystin variants in aquatic bodies compounded the problem. Although several analytical techniques for microcystin detection such as bioassay, ELISA, HPLC and LC-MS etc. have been already prevalent, the development of biosensors offered rapid and accurate detection, high reproducibility and portability. Sequencing of Microcystis spp., opened the new vistas towards the development of biosensor at molecular and genetic level. This review incorporates the current trends in the development of biosensors for microcystin detection in the light of state-of-the-art techniques. [Copyright &y& Elsevier]

Abstract: The effects of the sonication parameters, including the power and time, were investigated for the effective isolation of Scenedesmus sp. from environmental microalgae communities when using fluorescence-activated cell sorting (FACS). The selectivity, defined as the percentage of Scenedesmus sp. successfully isolated and grown in microplates, appeared as peaks in contour plots spanned by the sonication power and time. For fast screening of the optimal sonication conditions, correlations between the selectivity and the statistical parameters from the FACS analysis were investigated. A graphical comparison analysis of the contour plots showed a pattern similarity of over 82% between the coefficients of variation for the side scatter (SSC-CV) and the selectivity. This predictability of the optimal sonication conditions enabled a Scenedesmus sp. selectivity of ca. 2times using only one-third of the sonication condition sets arbitrarily chosen around the peaks of the SSC-CV, thereby saving resources and time for subsequent processes. [Copyright &y& Elsevier]