Modulation of Membrane and Reserve Fatty Acids of the Thraustochytrid <i>Aurantiochytrium mangrovei</i> by Light and Temperature Culture Conditions

Abstract

This study aimed to investigate the effects of temperature, illumination, and growth stage on the cell morphology, lipid content, and fatty acid (FA) composition in neutral lipids (NL) and polar lipids (PL) of Aurantiochytrium mangrovei, a thraustochytrid, widely known for its capacity to accumulate docosahexaenoic acid (22:6n-3, DHA). Experiments were conducted at three different temperatures (15°C, 20°C, and 25°C) under both illuminated and non-illuminated conditions. Illumination of the culture significantly increased OCFA (15:0 + 17:0) in PL by 42%, 6%, and 11% at 15°C, 20°C, and 25°C. Proportions of 15:0 + 17:0 in NL and PL increased with increasing temperature, being highest at 20°C in the exponential phase (7% in PL and 9% in NL) and at 25°C in the stationary phase (15% in PL and 32% in NL). The temperature also increased the DPAn-6 proportion during the exponential phase, from 2.5% to 5.9% in NL and from 5.5% to 11% in PL, whereas DHA (22:6n-3) tended to decrease. The resulting DHA/Docosapentaenoic acid (22:5n-6, DPAn-6) ratio in both NL and PL was highest in cultures at 15°C during the exponential phase. Cultivation of A. mangrovei at 15°C was favorable to a high DHA proportion (61% of total FA in PL and 68% in NL) and a high DHA/DPAn-6 (> 11 in PL and 23 in NL) ratio during the exponential phase. Further research is needed to better understand why DHA and DPAn-6, two very long-chain PUFA, are regulated in an opposite manner in response to changing temperature.