The combined effect of nitrogen source and silicate availability on the growth of the eicosapentaenoic acid-producing diatom Phaeodactylum tricornutum
摘要
The diatom Phaeodactylum tricornutum is one of the richest sources of the polyunsaturated fatty acid eicosapentaenoic acid (EPA), an essential nutrient in animal and human nutrition. Optimizing culture conditions to maximize biomass yield is crucial to any commercial process including microalgae. This research aimed to determine whether nitrogen source and silicate availability influence the growth attributes of this species. By providing N as nitrate, in the range of 8 to 33 mg N L-1, the strain incorporated all the available nitrate between day 4 and 8, the cultures at 50 and 66 mg N L-1 incorporated 100% of nitrate on day 12, while trials at 83 mg N L-1 kept available nitrate at the end of the culture (day 12). No significant differences were detected in the growth of the cultures between 33 and 83 mg N L-1, which could be explained by the ability of diatoms to accumulate nitrate within intracellular vacuoles. When N was supplied as urea (alone or 1:1 with nitrate) it was rapidly incorporated into the cell when combined with nitrate, while when it was the only source of N, its incorporation was slower, but the cultures reached higher cell densities. Growth parameters were similar between cultures supplied with nitrate or urea individually, while mixed supply showed lower growth parameters. Silicate at 5 or 20 mg L-1 did not affect the growth, total lipids or EPA content of P. tricornutum, with any of the nitrogen sources.