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Accueil du site → Doctorat → États-Unis → 1990 → Characterization of saline waters and lipogenic microalgae of the arid Southwest

Arizona State University (1990)

Characterization of saline waters and lipogenic microalgae of the arid Southwest

Ellingson, Stephen Bennett

Titre : Characterization of saline waters and lipogenic microalgae of the arid Southwest

Auteur : Ellingson, Stephen Bennett

Université de soutenance : Arizona State University

Grade : Doctor of Philosophy (PhD) 1990

Water samples were collected from 127 sites in the arid Southwest that supported abundant microalgal growth. The sampling locations contained water that was shallow (median 20 cm), warm (med. 27.0 C), alkaline (med. 8.0 SU) and saline (med. 6.035 mS cm$\sp-1$). In addition to measuring the aforementioned field parameters, the ionic composition (i.e. major cations and anions) of the water was assessed. Cluster analysis was used to divide the water samples into three major groups of similar ionic composition, with one cluster composed of three subcategories. The first major cluster, composed of three subcategories, represents a continuum with water dominated by sodium plus chloride and ranging to waters without dominant ions. The second major group was dominated by calcium plus sulfate and the third group was dominated by calcium plus alkalinity. Spatial patterns in the clusters were related to the recently developed USEPA ecoregions. Microalgae were collected from 206 planktonic, benthic or neustonic sampling locations in the arid Southwest. Microalgae were subjected to elevated salinities and light intensities before using agar plating techniques to isolate genera. Approximately 800 microalgal strains were isolated. During characterization experiments rapid microalgal growth occurred in SERI Type I or II Media at 10 mS cm$\sp-1$ and seawater. Subsequent characterization activities used the lipid specific probe Nile Red. A series of optimization experiments indicated that urea was a better nitrogen source than ammonia or nitrate for maximizing growth rates, culture density and lipid yield. Thirteen microalgal strains (3 cyanophytes, 3 chlorophytes and 7 chrysophytes) exhibited rapid growth and significant lipid accumulation, and were submitted to the SERI Culture Collection for inclusion in their listing of most promising aquatic species. The large number of microalgal strains isolated was reduce to 115 using a high-salinity screening protocol. Growth rates and biomass accumulation was greatest in Type I Medium. Lipid yields were higher in SERI Type II with the chrysophytes demonstrating the most dramatic increase. Subjecting microalgal strains to brief periods of nitrogen deprivation after logarithmic growth stimulated lipid storage.

Mots clés : Microbiology, microalgae, Biological sciences, Freshwater ecology, Botany

Accès au document : Proquest Dissertations & Theses

Page publiée le 30 janvier 2015, mise à jour le 30 décembre 2016