| Current practice in the mass culture of microalgae is limited to species which can be cultivated in chemically selective environments to prevent contamination from indigenous strains. The two commercial examples of microalgal products, health food and beta-carotene, require either high alkalinity or salinity to maintain the organisms from which they are derived, Spirulina and Dunaliella. The development of other products and processes involving microalgae is presently hampered by a lack of knowledge concerning the selective nature of the mass culture environment. Further limiting the scope of products is an incomplete understanding of the kinetic features of secondary metabolite production in mass cultures. This work has addressed both of these problems by carrying out an investigation into: species competition in laboratory models of mass culture environments; and lipid production as a function of light supply, cultivation environment, and nutrient deficiency.;The transient character of the AGP environment was reproduced in laboratory continuous cultures by an automated control system which could vary temperature, dissolved oxygen and pH over the diurnal cycle. To a first approximation, with the species studied, monoculture productivity was predictive of mixed culture success. Competition experiments between a Chlorella and Chaetoceros species, experiencing either a laboratory environment of constant conditions or a simulated out-door environment of diurnally varying conditions, resulted in opposite species dominance patterns.;The lipid content of eight strains of microalgae was determined under a range of conditions of nitrogen deficiency. Of the strains investigated, a Nannochloropsis species ("Q" strain) had the highest lipid content (50%) during nitrogen deficiency. Further studies of this organism, as a function of cultivation environment, light supply, and nitrogen status, indicated that regardless of cellular nitrogen content, lipid production was always greater in batch than continuous culture. (Abstract shortened with permission of author.).;In this study, a model of the Algal Growth Pond (AGP) was developed which incorporated design, and physico-chemical parameters to predict diurnal variations in temperature, pH, and dissolved oxygen. Simulated diurnal temperature profiles for earthen ponds located in Roswell, NM., and West Palm Beach, Florida were made for each of the four seasons. |
