STUDIES ON THE PRODUCTION OF USEFUL CHEMICALS, ESPECIALLY FATTY-ACIDS IN THE MARINE DIATOM NITZSCHIA-CONSPICUA GRUNOW

A local marine diatom, Nitzschia conspicua Grunow, was cultured in enriched synthetic seawater using flasks (agitated by magnetic stirring) and a 1.2 1 fermenter. Lipids, fatty acids, proteins, carbohydrates and ash of the flask cultures were determined at various stages of growth (day 3, 5, 7, 10, 13, 15 and 17). The fermenter culture was harvested during the stationary phase for similar chemical analyses. N. conspicua attained a higher biomass concentration during the stationary phase when cultured in the fermenter (188 mg dry weight l-1) than in flasks (140-151 mg dry weight l-1). However, both systems showed similar specific growth rates based on chlorophyll-a concentration. Appreciable amounts of the essential fatty acids 20:4 (0.6-4.7% total fatty acids) and 20:5 (1.9-4.7% total fatty acids) are present in this diatom. Maximal amounts of these fatty acids were produced after 7 days' growth (i.e. 2 days after the end of the exponential phase). Lipids, fatty acids, proteins, carbohydrates and ash varied with culture age in N. conspicua.