Effect of Temperature on Growth and Biochemical Composition (Sterols, α-tocopherol, Carotenoids, Fatty Acid Profiles) of the Microalga, Isochrysis galbana

Abstract

The microalga Isochrysis galbana Parke was grown in 100-l polyethylene bags filled with steril- ized seawater enriched with Wallerstein and Miquel nutrient medium (3:1) at two temperatures (18°C and 26°C), 2.5% salinity, and continuous illumination. Samples of microalgae were exam- ined during the exponential growth, stationary growth, and decay phases (days 18, 35, and 58, respectively). Stigmasterol constituted the main sterol group in all phases in both treatments, except during the exponential growth phase at 18°C. The highest concentration of α-tocopherol was 5.22 mg/100 g DW, reached in the decay phase of algae raised in 18°C. Likewise, the high- est total carotenoid (4.14 mg/g DW) and chlorophyll (2.87 mg/g DW) levels were obtained in algae raised in 18°C, during the exponential phase; the main pigments were chlorophyll a, c1, c2, and fucoxanthin. At 18°C, polyunsaturated fatty acids (PUFA) were the predominant fatty acid group, reaching 37.93% of the total fatty acids in the stationary phase. At 26oC, saturated fatty acids (SAF) were the predominant group of fatty acids. The present study suggests that the nutritional value (gross biochemical composition and fatty acid profile) of I. galbana Parke is, to a large extent, determined by the temperature at which it is grown and the harvest time.