GROWTH, LIPID PRODUCTION AND BIODIESEL POTENTIAL OF Chromulina freiburgensis Dofl., AN ACIDOPHILIC CHRYSOPHYTE ISOLATED FROM BERKELEY PIT LAKE

Microalgae remain a promising, but underdeveloped source of lipids for sustainable biodiesel. Some of the obstacles to cost-effective commercial-scale production have been culture contamination and expensive harvest methods. A chrysophyte isolated from Berkeley Pit Lake and identified as Chromulina freiburgensis, was found to grow rapidly in a pH 2.5 liquid medium and to amass numerous intracellular lipid bodies. This research addresses the scarcity of published knowledge on the topic of chrysophyte species as potential lipid sources for biodiesel. It investigates how growth phase, culture conditions, and harvest timing influence the quantity and composition of lipids produced by this alga. This research serves as a foundation for optimizing production of lipids that contain the most desirable fatty acid composition for biodiesel. Six experimental treatments, representing six different combinations of nutrient concentrations, were monitored and sampled during a 52-day growth period, while cellular lipid content was tracked by Nile Red fluorescence measurements. Lowering medium nitrogen concentration resulted in increased lipid production, which was further increased by lowering phosphorus concentration and supplementing with CO2. The combination of lowered nitrogen and phosphorus concentrations resulted in the highest proportion of C18:1 (50.1%) in the composition of fatty acid methyl esters from algal lipids, after approximately 22 days of stationary growth. The alga maintained its growth and favorable fatty acid composition with a modest increase in CO2. Although C. freiburgensis from Berkeley Pit Lake did not clearly demonstrate a high lipid content, its fatty acid composition is favorable for biodiesel production, and it has additional traits which may prove advantageous. Its acidic medium provides protection from culture contamination, and could potentially utilize acid mine drainage water. Fungal-assisted bioflocculation could then provide an economical means of harvest. This unique microalga is well ...