Songklanakarin Journal of Science and Technology (SJST) (Nov 2005)
Fatty acids composition of 10 microalgal species
Abstract
Fatty acids composition of 10 species of microalgae was determined at the exponential phase and the stationary phase. The microalgae consist of two species of diatoms, Bacillariophyceae, (Nitzschia cf. ovalis, Thalassiosira sp.) five species of green microalgae, Prasinophyceae (Tetraselmis sp.) and Chlorophyceae, (Dictyosphaerium pulchellum, Stichococcus sp., Chlorella sp., Scenedesmus falcatus) and three species of blue green microalgae, Cyanophyceae (Anacystis sp., Synechococcus sp., Synechocystis sp.).Medium for culture diatoms and green microalgae was F/2, and BG-11 media was used for Cyanophyceae. The microalgae were cultured beneath light intensity 143 μEm-2s-1, light: dark illustration 12:12 hrs., temperature 28ºC, and salinities 8-30 psu. The microalgae were harvested for analyzing fatty acid by centrivugal machine at 3500 rpm. for 5 min. at temperature 20ºC and stored at -80ºC prior to analysis.Fatty acids composition of microalgae differed from species to species. The majority fatty acids composition of diatoms at the exponential phase and the stationary phase were C16:1n-7 (17.12-31.47% and 28.22-42.02%), C16:0 (13.25-19.61% and 18.83-20.67%), C20:5 n-3 (16.65-26.67% and 11.32-23.68%) respectively. The principle fatty acids composition of green microalgae, Prasinophyceae, Tetraselmis sp. were C18:3n-3 (16.17-16.67%), C16:0 (15.33-17.45%), C18:1n-9 (12.25-15.43%), C18:2n-6 (9.66-19.97%). The fatty acids composition of green microalgae, Chlorophyceae, were C18:3 n-3 (20.02-26.49% and 15.35- 30.63%), C16:0 (5.76-17.61% and 11.41-20.03%), C18:2n-6 (4.67-17.54% and 7.48-20.61%) respectively. The major amounts of fatty acids content of blue green microalgae were C16:1n-7 (9.28-34.91% and 34.48- 35.04%), C14:0 (13.34-25.96% and 26.69-28.24%), C16:0 (5.89-29.15% and 5.70-16.81%) except for Anacystis sp.which had a high amount of C18:3 n-3 (23.18-27.98%) but low amount of C14:0 (3.66-4.98%).Bacillariophyceae contained the highest amount of highly unsaturated fatty acids (HUFAs) at both growth phases. Prasinophyceae had a small amount while in Chlorophyceae and Cyanophyceae they were not detected. Nitzschia cf. ovalis and Thalassiosira sp. had amount of C20:4n-6 (0.08-4.40%),C20:5 n-3 (11.32- 26.67%) and C22:6 n-3 (0.80-4.20%) respectively. Tetraselmis sp. had amounts of C20:4n-6 and C20:5 n-3 ranging from 0.99-1.13% and 4.18-4.70% respectively. In conclusion, Nitzschia cf. ovalis and Thalassiosira sp. would serve as good nutritional sources of HUFAs for aquaculture animals.
