Date of Award

2013

Degree Type

Thesis

Department

Biological, Geological and Environmental Sciences

First Advisor

Wolin, Julie

Subject Headings

Algal biofuels, Scenedesmus, Microalgae, Algal biofuels, Algae -- Adaptation, Freshwater algae, Algae -- Growth, Scenedesmus dimorphus salt stress lipid saltwater adaptation brackish water adaptation algal adaptation freshwater algae algal biomass semi-batch closed system open system growth rates contamination

Abstract

The fresh water microalga Scenedesmus dimorphus is of interest in the microalgae to biofuel field. With a 26 dry weight as lipid content and a potential doubling time of 60-70 hours, it is a viable candidate for biofuel production. Recent studies have focused on optimizing the growth rate and lipid content of S. dimorphus by finding ideal light, carbon-dioxide flow rates, nutrient composition of media, pH, temperature, and implementation of various stresses in the growth environment. Adaptation of S. dimorphus to a saline environment would make it a viable biofuel stock world-wide. This saline adaptation experiment was conducted in two stages, using TSG as a unit of measurement for salt density of the growth environments. The goal for the first stage of this study was to determine if S. dimorphus was capable of adapting to increased salinity levels in a closed environment, where competition with other algal species and bacteria were limited to non-existent. The second stage of experimentation determined if the adapted S. dimorphus could survive in a large scale open, marine system. Adaptation of S. dimorphus from fresh water to brackish water was successfully completed after a 220 day semi-batch process. Adaptation to brackish water environments yielded no significant difference in growth rates when compared to fresh water environments. Adapted S. dimorphus obtained a growth rate of 0.47 ± 0.14 day-1 in a 1.015 TSG small-scale, closed system environment, while the freshwater control obtained a growth rate of 0.56 ± 0.05 day-1. Adapted S. dimorphus obtained a growth rate of 0.35 ± 0.15 day-1 in a 1.015 TSG large-scale, open system environment, which was not statistically different from that of freshwater S. dimorphus in freshwater media, with growth rate of 0.61 ± 0.31 day-1. Lipid content in the 1.015 TSG small-scale, closed system was calculated to be 23 ± 10 , with the large scale, open system yielding lipid content results of 15± 9 . The microalga S. dimorphus is capable of

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