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Chlorococcum

About: Chlorococcum is a(n) research topic. Over the lifetime, 268 publication(s) have been published within this topic receiving 7317 citation(s).


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Journal ArticleDOI
TL;DR: The mass transfer coefficient (k) for lipid extraction under supercritical conditions was found to increase with fluid dielectric constant as well as fluid density, and decreasing temperature and increasing pressure resulted in increased lipid yields.
Abstract: This study examines the performance of supercritical carbon dioxide (SCCO(2)) extraction and hexane extraction of lipids from marine Chlorococcum sp. for lab-scale biodiesel production. Even though the strain of Chlorococcum sp. used in this study had a low maximum lipid yield (7.1 wt% to dry biomass), the extracted lipid displayed a suitable fatty acid profile for biodiesel [C18:1 (∼63 wt%), C16:0 (∼19 wt%), C18:2 (∼4 wt%), C16:1 (∼4 wt%), and C18:0 (∼3 wt%)]. For SCCO(2) extraction, decreasing temperature and increasing pressure resulted in increased lipid yields. The mass transfer coefficient (k) for lipid extraction under supercritical conditions was found to increase with fluid dielectric constant as well as fluid density. For hexane extraction, continuous operation with a Soxhlet apparatus and inclusion of isopropanol as a co-solvent enhanced lipid yields. Hexane extraction from either dried microalgal powder or wet microalgal paste obtained comparable lipid yields.

609 citations

Journal ArticleDOI
Abstract: The excretion of photoassimilated carbon was determined for 22 species of unicellular marine algae in culture during periods of log-phase growth and for some natural marine phytoplankton populations from Vineyard Sound and the Gulf of Maine. Carbon 14 tracers gave some information about the composition of the excreted material. Most of the algae excreted 3-6s of their photoassimilated carbon during logarithmic growth. A few species excreted as much as 10-25s under the same conditions. Algae subjected to two different light intensities, 3,000 lux and 25,000 Iux, varied less than 30% in their relative rates of excretion. However, algae exposed to direct sunlight (lOO,OOO120,000 lux) had very high excretion rates, possibly resulting from damage to the cells by photooxidation. Glycolic acid formed 938% of the total carbon excretion in Olisthodiscus sp., Chaetoceros pelagicus, Chlorococcum sp. and Skeletonema costatum. Lower relative amounts were excreted by most of the species studied. Skeletonema costatum excreted considerably more glycolic acid at light intensities below 15,000 lux than above. This is contrary to the findings of other investigators using the freshwater alga Chlorella pyrenoidosa. The amount of carbon excreted as protein ranged from 0.2 to 5.9%, and that excreted as chloroform-soluble material ranged from 2.8 to 10.3% of the total. After electrodialysis, 12-340/O of the compounds were recovered in the anion fraction. Considerable quantities of amino acids and peptides were also detected as excretory products of many of the algae. A few species excreted a single substance almost exclusively. Thus, Chlorella sp. excreted mainly proline, Dunaliellu tertiolectu mainly glycerol, and Olisthodiscus sp. mainly mannitol. Apparently healthy populations of natural phytoplankton excreted 4-16s of their photoassimilated carbon. However, 17-38s was excreted by a sample taken at the end of a diatom bloom, when a large number of empty frustules was present.

533 citations

Journal ArticleDOI
Zechen Wu1, Yi Zhu1, Weiya Huang1, Chengwu Zhang1, Tao Li1, Yuanming Zhang1, Aifen Li1 
TL;DR: This study revealed that the microalgal biomass concentrations and released polysaccharide from microalgae could influence the flocculation efficiencies, and neutralizing pH and then supplementing nutrients allowed the flocculated medium to maintain an approximate growth yield to that of the fresh medium in algal cultivation.
Abstract: Flocculation induced by pH increase for harvesting microalgae and reuse of flocculated medium were evaluated. Increasing the medium pH value induced the highest flocculation efficiency of up to 90% for freshwater microalgae (Chlorella vulgaris, Scenedesmus sp., Chlorococcum sp.) with low/medium biomass concentrations and marine microalgae (Nannochloropsis oculata, Phaeodactylum tricornutum). The mechanism may be explained that Mg(2+) in the growth medium hydrolyzed to form magnesium hydroxide precipitate, which coagulated microalgal cells by sweeping flocculation and charge neutralization. Additionally, this study revealed that the microalgal biomass concentrations and released polysaccharide (RPS) from microalgae could influence the flocculation efficiencies. Furthermore, neutralizing pH and then supplementing nutrients allowed the flocculated medium to maintain an approximate growth yield to that of the fresh medium in algal cultivation. These results suggest that the method presented here is effective, and allows the reuse of the flocculated medium, thereby contributing to the economic production from algae to biodiesel.

314 citations

Journal ArticleDOI
TL;DR: This strain represents a potential source of lutein, a commercially interesting carotenoid of application in aquaculture and poultry farming, as well as in the prevention of cancer and diseases related to retinal degeneration.
Abstract: Fifteen strains of chlorophycean microalgae have been investigated with regard to their carotenoid profile. Lutein, beta-carotene and violaxanthin were present in virtually all of the strains, lutein, in general, being the most abundant carotenoid, whereas canthaxanthin and astaxanthin were found in some strains only. Chlorella fusca SAG 211-8b, Chlorococcum citriforme SAG 62.80, Muriellopsis sp., Neospongiococcum gelatinosum SAG B 64.80 and Chlorella zofingiensis CCAP 211/14 exhibited high lutein levels, the latter strain containing in addition substantial amounts of astaxanthin. Muriellopsis sp. was further characterized, since besides a high lutein content (up to 35 mg l(-1) culture), it had the highest growth rate (up to 0.17-0.23 h(-1)) and maximal standing cell density (up to 8 x 10(10) cells l(-1) culture). These levels of lutein are in the range of those reported for astaxanthin in Haematococcus and for beta-carotene in Dunaliella, microalgae of recognized interest for the production of these carotenoids. Lutein content of Muriellopsis sp. increased during the exponential phase of growth, with the highest value being recorded in the early stationary phase. Maximum levels of lutein in Muriellopsis sp. cultures were recorded at 20-40 mM NaNO3, 2-100 mM NaCl, 460 micromol photon m(-2) s(-1), pH 6.5 and 28 degrees C, conditions which were, in general, also optimal for cell growth. Growth-limiting conditions, such as pH values of 6 or 9 and a temperature of 33 degrees C, were found to stimulate carotenogenesis in Muriellopsis sp. This strain represents a potential source of lutein, a commercially interesting carotenoid of application in aquaculture and poultry farming, as well as in the prevention of cancer and diseases related to retinal degeneration.

262 citations

Journal ArticleDOI
TL;DR: The 185rDNA trees clearly demonstrate the non‐monophyly of the Chlamydomonadales and Chlorococcales, suggesting that vegetative morphology does not reflect phylogenetic relationships in the CW group.
Abstract: SUMMARY Nuclear-encoded small subunit ribosomal RNA gene (185rDNA) sequences were determined for Chlamydomonas moewusii Gerloff and five chlorococcalean algae (Chlorococcum hypnosporum Starr; Chlorococcum oleofaciens Trainor et Bold; Chlorococcum sp.; Tetracystis aeria Brown et Bold; Protosiphon botryoides (Kutzingl Klebs). All these algae are characterized by a clockwise CCW) flagellar apparatus. Phylogenetic trees were constructed from sequences from these algae together with 20 green algae. All algae with a CW flagellar apparatus form a monophyletic clade (CW group). Three principal clades can be recognized in the CW group, although no morphological character supports monophyly of any of these three clades. The 185rDNA trees clearly demonstrate the non-monophyly of the Chlamydomonadales and Chlorococcales, suggesting that vegetative morphology does not reflect phylogenetic relationships in the CW group. The paraphyly or polyphyly of the genus Chlamydomonas and Chlorococcum are also revealed. Present analysis suggests that the presence or absence of a zoospore's cell wall and the multinucleate condition have limited taxonomic values at higher taxonomic ranks.

193 citations

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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20221
202121
202013
201923
201812
201714