Culturing Chaetoceros muelleri using simplified mediums-effects on production and biochemical quality

Inland shellfish aquaculture depends on the large scale culture of live microalgae as food source. The quality of the microalgae cultured is situation specific and influenced by aspects such as like scale, batch/continuous culture, irradiance, nutrient concentration and culture medium. In the framework of the integrated fish-shellfish-microalgae inland aquaculture project Zeeland Sole (Zeeuwse Tong) we studied the impact of culture medium and nutrient ratios on the culture and biochemical composition of Chaetoceros muelleri, a marine diatom. This marine diatom is widely used in shellfish hatcheries due to its high lipid and fatty acid composition. The objectives of this study were to determine the impact of the different (simplified) culture mediums on the biochemical composition, longevity and production of microalgae cultures. Batch cultures of this species were cultured in 10 L vessels under at 19under constant light. Walne medium (Walne, 1970) enriched with silica was used as control. Four other mediums were prepared using only silica, vitamins, iron and manganese concentration from Walne medium and different nitrogen sources/concentrations (table 1). The phosphorus concentration was maintained constant in all mediums, resulting in different N/P ratios of the mediums. The cellular concentration of the cultures were determined throughout the batch culture until collapse. The biochemical composition of the microalgae (proteins, lipids, carbohydrates, dry weight, polar, neutral and total fatty acids) and the nutrient concentration in culture were determined on the exponential phase and stationary phase (two treatments). Cultures grown in mediums B and C had a longer longevity (21 days) and achieved higher maximum cellular concentration (9.6*106 cells/mL and 12 *106 cells/mL, respectively) than cultures grown in Walne medium (10 days, 8.2*106 cells/mL) and mediums A (9 days, 6.1*106 cells/mL) and D (14 days, 8.7*106 cells/mL). The composition of the microalgae grown in the different mediums and the nutrient concentration of the cultures will be reported and the suitability of the mediums for large scale production will be discussed.