Microalgae chemical composition in semi-intensive culture:Chaetoceros gracilis Schutt, Isochrysis galbana Parke and Thalassiosira weissflogii (Grunow) G. Fryxell & Hasle.

Abstract

This work aimed to evaluate the chemical composition of Chaetoceros gracilis, Isochrysis galbana and Thalassiosira weissflogii, cultivated according to Aqualider Company methodology.  The species were cultivated in f/2 Guillard environment with sustained temperature and illumination until reaching 20 L in plastic bags.  The analyses were executed at the beginning of the exponential growth phase. The I. galbana specie showed the highest cellular density (3,295 ±47.73 x 106 cel L-1) with a high meaningful difference from the other species, the highest amount of soluble carbohydrate (0.09 ±0.002 mg.L-1), followed by C. gracilis (0.06 ±0.001 mg.L-1) and by T. weissflogii (0.05 ± 0.001 mg.L-1) with significant differences among species and the highest amount of nitrate (0.15 mg.L-1), phosphor (0.21 mg.L-1) and magnesium (2.90 mg.L-1) with superior significant differences among species. The T. weissflogii specie showed the highest values for sodium (6.59 mg.L-1), potassium (0.91 mg.L-1) and sulphur (0.94 mg.L-1).  As to chlorophyll a amount, C. gracilis showed the highest value (3.74 ±0.26 mg.L-1), followed by I. galbana (1.87 ±0.08 mg.L-1) and T. weissflogii with the lowest value (0.96 ±0.08 mg.L-1), also with significant differences among species. The species presented different chemical composition, which is characteristic of the analyzed culture phase, being indicated for this kind of cultivation, Chaetoceros gracilis, because of its high chlorophyll a, soluble protein and carbohydrates and total free amino acids amount.