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

Shiva Rezaei Motlagh,Razif Harun,Siti Aslina Hussain,Ramin Khezri,Amal A Elgharbawy,Dayang Radiah Awang Biak,Cecilia Devi Wilfred

doi:10.3390/biom10081149

Abstract

This study performs a screening of potential Ionic Liquids (ILs) for the extraction of Docosahexaenoic Acid (DHA) compounds by the calculation of capacity values. For this purpose, a Conductor-Like Screening Model for Real Solvents (COSMO-RS) was employed to study the molecular structures of the ILs, and therefore, predict their extraction potential. The capacity values of 22 anions combined with 16 cations based ILs, were investigated to evaluate the effectiveness of ILs in the extraction of DHA. It was found that among the investigated ILs, a combination of tetramethyl ammonium with SO4 or Cl was the best fit for DHA extraction, followed by pyrrolidinium, imidazolium, pyridinium and piperidinium. Furthermore, it was observed that the extraction capacity and the selectivity of ILs decreased with an increase in alkyl chain length; therefore, ethyl chain-ILs, with the shortest chain lengths, were found to be most suitable for DHA extraction. The predicted results were validated through the experimentally calculated extraction yield of a DHA compound from Nannochloropsis sp. Microalgae. Five selected ILs, namely [EMIM][Cl], [BMIM][Cl], [TMAm][Cl], [EMPyr][Br] and [EMPyrro][Br], were selected from COSMO-RS for empirical extraction purposes, and the validation results pinpointed the good prediction capabilities of COSMO-RS. The findings in this study can simplify the process of selecting suitable ILs for DHA extraction and reduce the number of required empirical evaluations.

Highlights

In nature, omega-3 polyunsaturated fatty acids are typically found in three distinct forms of: eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and alphalinolenic acids (ALA)
In a previous study, the potential of different types of Ionic Liquids (ILs) for EPA (C:20, n-3) compound extraction was investigated through the calculation of capacity values using the COSMO-RS prediction tool
The significance of this study is that through the reported screening methodology, one can determine the capacity values of numerous ILs as green solvents to apply to DHA extraction without having to perform a substantial number of expensive experiments

Summary

Introduction

Omega-3 polyunsaturated fatty acids (omega-3 PUFA) are typically found in three distinct forms of: eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and alphalinolenic acids (ALA). COSMO-RS was used to predict the selectivity and distribution coefficient of ILs ([EMIM][EtSO4] and [EMIM][CH3COO]) for use as a solvent to extract benzothiophene from n-hexane. In a previous study, the potential of different types of ILs (diverse cation/anion combination) for EPA (C:20, n-3) compound extraction was investigated through the calculation of capacity values using the COSMO-RS prediction tool. We performed a screening evaluation using the COSMO-RS method to determine the capacity values of 352 cations–anions combination base ILs in order to identify the most suitable types to apply to solid–liquid extraction of DHA from microalgae. The significance of this study is that through the reported screening methodology, one can determine the capacity values of numerous ILs as green solvents to apply to DHA extraction without having to perform a substantial number of expensive experiments. The most important aspect of this study is that it predicts the capacity values of a variety of ILs in solid–liquid extractions from microalgae biomasses, while most related research was focused on liquid–liquid extraction

Computational Methods of COSMO-RS

Process Stages in Screening ILs

The Effect of Alkyl Chain Length on the Capacity Value of ILs

Experimental Validation of COSMO-RS Predicted Extraction Capacity of DHA

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