Efficient Extraction of a Docosahexaenoic Acid (DHA)-Rich Lipid Fraction from Thraustochytrium sp. Using Ionic Liquids

Abstract

Polyunsaturated fatty acids (PUFAs) play a significant role in the modulation and prevention of various diseases, and hence are attracting increasing attention from the biotech industry. Thraustochytrids are marine heterokonts that exhibit robust growth rates, high PUFA content, and more specifically, a large percentage of omega-3 fatty acids like docosahexaenoic acid (DHA). Recently, ionic liquids (ILs) have been shown to improve the efficiency of organic solvent extraction of oils from wet oleaginous yeast and microalgae under mild conditions. Two ILs, the imidazolium 1-ethyl-3-methylimidazolium ethylsulfate [C2mim][EtSO4] IL and the phosphonium (tetrabutylphosphonium propanoate [P4444][Prop]) IL were assessed for their ability to facilitate extraction of PUFA-containing lipids from a Thraustochytrium sp. (T18) through efficient cell wall disruption. The oil extracted after IL pretreatment was further characterized with respect to fatty acid methyl ester (FAME) composition, while the effects of process parameters, such as the ratio of ionic liquid to co-solvent, the mass ratio of microalgae to the mixture of ionic liquid, and type of co-solvent were also investigated for both ILs. The results indicate that these ILs can disrupt the cells of Thraustochytrium sp. when mixed with a co-solvent (methanol), and facilitated the recovery of oils over a large degree of dewatered Thraustochytrium biomass (0–77.2 wt% water) in a short period of time (60 min) at ambient temperature, hence demonstrating a water compatible, low-energy, lipid recovery method. The lipid recovery was not affected by repeated usage of recycled ILs (tested up to five times).

Prediction of Potential Ionic Liquids (ILs) for the Solid–Liquid Extraction of Docosahexaenoic Acid (DHA) from Microalgae Using COSMO-RS Screening Model

“…According to the results, C22:6n-3 (DHA) was the major component found in all extracts, indicating that T18 was a good source of DHA. Furthermore, the study showed that the extraction was not of high quality and the ILs used were unable to extract the DHA with high selectivity; instead they extracted the total lipids available without oxidizing the unsaturated bonds [76]. This is in agreement with the COSMO-RS results, which showed that propanoate is indeed an excellent option for extraction when combined with ethyl cations.…”

“…In a previous study, two ILs (imidazolium 1-ethyl-3-methylimidazolium ethyl sulfate [EMIM][EtSO 4 ] and phosphonium (tetrabutyl phosphonium propanoate [P4444][Prop])) were used as extracting solvents to perform PUFA extraction from Thraustochytriumsp . (T18) [ 76 ]. According to the results, C22:6n-3 (DHA) was the major component found in all extracts, indicating that T18 was a good source of DHA.…”

A review on microalgae cultivation and harvesting, and their biomass extraction processing using ionic liquids

“…The study on the extraction of DHA from Thraustochytrium sp. biomass reported 1-ethyl-3-methylimidazolium ethylsulfate and tetrabutylphosphonium propionate, with the use of IL: methanol at 1:10 and 1:4 ratio, respectively, achieved lipid extraction yield of 91% [106].…”

COSMO-RS Based Prediction for Alpha-Linolenic Acid (ALA) Extraction from Microalgae Biomass Using Room Temperature Ionic Liquids (RTILs)

“…In this context, Cheong et al suggested the correlation of n-3 PUFA extraction and structure of ILs (aromatic/delocalized cation) for the effective extraction of PUFA [46]. The short alkyl chain was used in a recent study [49]. Two types of ILs were used in the extraction of PUFA-containing lipids from Thraustochytrium sp.…”