Effect of high frequency of intermittent light on the growth and fatty acid profile of Isochrysis galbana

Abstract

The marine microalga Isochrysis galbana was cultured under different light regimes to examine the changes in growth and fatty acid profile. We have obtained preliminary results that I. galbana cultured under white intermittent light for 24hday−1 shows better growth than continuous white light with light/dark (L/D) cycles of 12h/12h. In this study, we searched for an effective intermittent light color for the growth of I. galbana. Control cultures were grown under white continuous light, with a photon flux density at 104μmolm−2s−1 with L/D cycles of 12h/12h. The other cultures were grown under a photon flux density of 52μmolm−2s−1 of 24h flashing per day, and white, red, and blue intermittent light at 10,000Hz as L/D cycles of 50μs/50μs. After 6days of cultivation, the cell density of the sample cultured under blue intermittent light was significantly higher than those of the others. The lipid contents in I. galbana were 98mgL−1 from the culture under constant white light and 155mgL−1 from the culture under blue intermittent light. Total lipids from I. galbana were separated into neutral lipids (29–35%), glycolipids (38–47%), and phospholipids (20–28%). The light condition did not affect the ratio of lipid classes or the fatty acid composition of total lipids, neutral lipids, glycolipids, or phospholipids from I. galbana. The amounts of neutral lipids, glycolipids, and phospholipids obtained from culture medium were the highest under blue intermittent light (3.27, 4.71, and 2.48mgL−1, respectively). The highest amounts of phospholipids and DHA were recovered from I. galbana cultured under blue intermittent light.