Date of Award

Fall 2007

Project Type

Thesis

Program or Major

Chemical Engineering

Degree Name

Master of Science

Abstract

Oil extraction from microalgae is an important process for lab analysis, the nutraceutical industry, and it will be important to growing field of algal biofuels. In this thesis, six strains of high-oil microalgae were screened for neutral lipid content and ease of culturing. One of these six, Chlorella sp., was cultured under various growth conditions to determine the settings to produce both the most cells and the highest neutral lipid content per cell. With this information, Chlorella sp. was cultured in large batches to produce sizable harvest quantities (10's of grams dry cells). During large scale culturing, cell concentration data, fluorometric (neutral lipid content) data, and pH data were collected to provide more information about the culture growth behavior and to properly time harvests. Harvested cells were centrifuged and freeze-dried for solvent extraction and in situ biodiesel production experiments. From freeze-dried cells, the total lipid mass was determined gravimetrically to be 8-10% of the dry mass, based on the solvent extraction method of Bligh and Dyer (1959). Solvent extracted lipids were derivatized to Fatty Acid Methyl Esters (FAMEs) using methanol and a base catalyst (potassium hydroxide). In situ FAME production was accomplished by adding a methanol/potassium hydroxide solution directly to freeze-dried cells and treating with high-power ultrasonication. Methanol amount, potassium hydroxide concentration, and ultrasonication time and power, were all examined for their effect on FAME production. Analysis of both solvent extraction produced FAMEs and in situ produced FAMEs was accomplished with a gas chromatograph equipped with a special FAME analysis capillary column and a Flame Ionization Detector. Pure FAME reference standards and an internal standard were used to help identify chromatographic data. For the freeze-dried cells used, the in situ FAME production was able to produce 150% of the FAMEs identified from solvent extracted lipid samples.

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