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Aurantiochytrium can produce significant amounts of omega-3 fatty acids, specifically docosahexaenoic acid and docosapentaenoic acid. Use of a glucose-based medium for heterotrophic growth is needed to achieve a high growth rate and production of abundant lipids. However, heat sterilization for reliable cultivation is not appropriate to heat-sensitive materials and causes a conversion of glucose via browning (Maillard) reactions. Thus, the present study investigated the use of a direct degradation of Peracetic acid (PAA) for omega-3 production by Aurantiochytrium. Polymer-based bioreactor and glucose-containing media were chemically co-sterilized by 0.04% PAA and neutralized through a reaction with ferric ion (III) in HEPES buffer. Mono-cultivation was achieved without the need for washing steps and filtration, thereby avoiding the heat-induced degradation and dehydration of glucose. Use of chemically sterilized and neutralized medium, rather than heat-sterilized medium, led to a twofold faster growth rate and greater productivity of omega-3 fatty acids.

In this study, lipid extraction from Aurantiochytrium sp. was performed using a molten-salt/ionic-liquid mixture. The total fatty acid content of Aurantiochytrium sp. was 478.8 mg/g cell, from which 145 mg/g cell (30.3% of total fatty acids) of docosahexaenoic acid (DHA) was obtained. FeCl3·6H2O showed a high lipid extraction yield (207.9 mg/g cell), when compared with that of [Emim]OAc, which was only 118.1 mg/g cell; notably however, when FeCl3·6H2O was mixed with [Emim]OAc (5:1, w/w), the yield was increased to 478.6 mg/g cell. When lipid was extracted by the FeCl3·6H2O/[Emim]OAc mixture at a 5:1 (w/w) blending ratio under 90 °C, 30 min reaction conditions, the fatty acid content of the extracted lipid was a high purity 997.7 mg/g lipid, with most of the DHA having been extracted (30.2% of total fatty acids). Overall, lipid extraction from Aurantiochytrium sp. was enhanced by the synergistic effects of the molten-salt/ionic-liquid mixture with different ions.

In this study, acid-catalyzed hot-water extraction of docosahexaenoic acid (DHA)-rich lipids from Aurantiochytrium sp. was performed, and its yield-enhancing effects were investigated. The total fatty acid content of the Aurantiochytrium sp. was 482.5mg/g cell, of which 141.7mg/g cell (29.4% of total fatty acids) was DHA. The lipid-extraction yield by acid-catalyzed hot-water treatment was compared with those by organic solvents. Among the various acid-catalyzed hot-water treatment conditions, the most optimal were 1.00% H2SO4 concentration, 100°C, 30min, under which the lipid-extraction yield was 472.4mg/g cell, and most of the DHA was extracted (29.2% of total fatty acids). Acid-catalyzed hot-water extraction treatment markedly improved the lipid-extraction yield of Aurantiochytrium sp., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Although nitrogen starvation is frequently used to increase lipid contents in microalgae, it has a negative effect on cellular growth. Since light supply is essential for photosynthetic organisms, the effects of cultivation under monochromatic illumination on the growth and lipid contents of Nannochloropsis gaditana were assessed. Continuous cultivation under blue and red light conditions improved the productivity and physical properties for biodiesel from this microalga. FAME yield was twofold higher under red light than under normal white light (21.12% vs 11.35%), with no significant difference in growth rates. Blue and red light increased photosynthetic oxygen evolution, carbon fixation and nutrient uptake. In total, more significant physiological changes were observed under red than under blue light. These results show that red light illumination may be useful for enhancing lipid production by N. gaditana, with the increased photosynthetic reducing equivalents induced by red light which could be deposited as lipids and carbohydrates., (Copyright © 2014 Elsevier Ltd. All rights reserved.)