University of California, San Diego William H. Thomas 1980 — 1983 XK-0-9111-1

Work carried out under this subcontract represented one of the first attempts by an ASP subcontractor to characterize the productivity and lipid yields of various microalgae. Six algal strains (B. braunii, Dunaliellaprimolecta, Isochrysis sp., Monallanthus salina, Phaeodactylum tricornutum, and Tetraselmis sueica) were obtained from existing culture collections and analyzed with respect to lipid, protein, and carbohydrate content under various growth conditions. For these experiments, all cultures except for B. braunii were grown in natural seawater that was enriched with N, P, and trace metals. B. braunii was grown in an artificial seawater medium. Initial experiments to determine productivities of these species were performed using batch cultures in 9-L serum bottles. Of the strains tested, the highest growth rates were observed with P. tricornutum (Thomas strain) and M. salina.

Additional experiments were performed in plexiglas vessels that were 5 cm thick, 39 cm deep, and 24 cm wide (surface area ~940 cm2). The cultures were illuminated from the side with a 2,000-watt tungsten-halide lamp, which was placed behind a water/CuSO4 thermal filter. In these experiments, the cultures were typically maintained for 40 to 90 days. In the early stages of an experiment, the cultures were maintained in a batch mode, and then converted to a continuous or semi-continuous dilution mode. V arious culture parameters (including light intensity, dilution rate, and N status) were manipulated during the course of these experiments to determine their effects on the productivities and proximate chemical composition of the strains. The results of these experiments with each species tested are discussed below. These experiments are difficult to compare because the experiments were all carried out slightly differently (i. e., different light intensities, different culturing methods [batch, semi-continuous, and continuous], different means of obtaining N-deficient cultures, and inconsistent use of a CuSO4 heat filter, which resulted in differences in light quality and culture temperature). Nonetheless, the general conclusions of this study are of interest.