Microwave-assisted three-liquid-phase salting-out extraction of docosahexaenoic acid (DHA)-rich oil from cultivation broths of Schizochytrium limacinium SR21

Abstract The extraction and separation of docosahexaenoic acid (DHA)-rich oils, proteins, and polysaccharides from microalgae is a challenge for industrial commercialization of DHA, such as drying and dewatering, cell wall disruption, laborious conventional extraction procedures and exploitation of large volumes of solvents. To address these concerns, a novel microwave-assisted three-liquid-phase salting-out extraction (MA-TLPSOE) was used to separate DHA-rich oils, proteins, and polysaccharides from wet cultivation broths of Schizochytrium limacinum SR21. The optimized MA-TLPSOE system was composed of 30% (w/w) n-hexane/13% (w/w) ethanol/9% (w/w) sodium carbonate and treated at high microwave power (650 W) for 30 seconds. Under optimized conditions, 100 ± 0.59% oil and 100 ± 0.64% DHA were partitioned in the top n-hexane phase while 93.75 ± 0.25% of polysaccharides and 92.96 ± 0.43% of proteins were distributed in the solid-phase interface. The effects of microwave power and duration, sodium carbonate, n-hexane, ethanol concentration and extraction time were studied. When the optimized system was enlarged from 20 g to 60 g, the yields of all effective components were almost the same. Thus, the MA-TLPSOE system is a promising and attractive technology, which could be used for the separation and extraction of various effective ingredients from complex natural products in a single step with significant recovery yield.