Growth and biochemical profile of Chaetoceros muelleri cultured in batch and semicontinuous systems

Abstract

We characterized the growth and biochemical composition of a Chaetoceros muelleri strain from the Araya Peninsula, Sucre, Venezuela. The microalga was cultured under laboratory conditions (25 ± 1ºC, 156 µE m^–2 s^–1 and 12:12 photoperiod) during 13 days, using two culture methods: batch and semicontinuous culture with a daily renewal rate of 30%. Cell density was determined and cells from each treatment were measured. The protein, lipid, carbohydrate and fatty acid contents were quantified to compare the quality of the Araya strain in both culture systems. Cell density showed little variability in the semicontinuous system during the steady-state phase (1.3 10⁶ cells mL^–1 on average), but increased significantly in the batch system, reaching 3.5 106 cells mL^–1. Proteins, lipids and carbohydrates did not show significant variations in the semicontinuous system, with mean values of 21.4 ± 0.8, 18.4 ± 0.8 and 4.1 ± 0.1 pg cells^–1, respectively. In the batch system, however, these macromolecules showed greater variability: proteins 3.5–21.1 pg cells^–1, lipids 8.5–11.6 pg cells^–1 and carbohydrates 4.2–18.1 pg cells^–1. Higher levels of saturated (47.5%) and monounsaturated (34.8%) fatty acids were found in the semicontinuous system, whereas the content of polyunsaturated fatty acids (31.4%) was higher in the batch system, in particular of eicosapentaenoic acid (EPA, 20:5 n-3) (16 ± 2% of total fatty acids). Cell size did not vary significantly in the two culture systems and the mean width and length were 5 and 7.5 µm, respectively. The Araya strain of C. muelleri can be used as a food source for cultured larvae, the semicontinuous system providing a more stable nutritional quality.