Best growth and FCR were obtained with microalgae grown with 8 mg atom N 1-l
but it should be noted that the conversion of nutrients into the microalgal biomass was
very low with this nutrient concentration. Only 27% of the supplied nitrogen was
converted into algal protein, whereas almost 100% of the added nitrogen was incorporated
in microalgae cultures at a nutrient concentration of 2 mg atom N 1-l (Fabregas et
al., 1995). This means that at 8 mg atom N 1 -I it converts only 2.16 mg atom N l- ’ into
protein while at 2 mg atom N 1-l it converts 2 mg atom N 1-l into protein. This is an
important point to be taken into account for the cost calculations of biomass production.