Fractionation of isochrysis galbana proteins, arabinans, and glucans using ionic-liquid-based aqueous biphasic systems

Isochrysis galbana (I. galbana) is a microalgae species rich in biomolecules of high commercial value and industrial relevance. Despite the numerous studies done on the extraction of different compounds from microalgae, the complete valorization of the biomass under the biorefinery concept is scarce or even inexistent. The mixture of different compounds found in the different extracts obtained from the microalgae biomass is one of the most important drawbacks in the field. Despite the large interest of academia and industry in the different classes of bioactive compounds composing microalgae, these are still poorly explored due to the low efficiency of the downstream processes used up to date. In this context, this work proposes the development of an efficient purification process by applying ionic liquid (IL)-based aqueous biphasic systems (ABS) to separate proteins from arabinose- and glucose-rich polysaccharides. For this purpose, the nature of the inorganic salt, the IL structural features (anion and alkyl chain length) and the extraction point (using different inorganic salt concentrations) were the conditions optimized. After the proper selection of the most performant IL-ABS (%EEcarb = 71.21 ± 5.21% to the bottom phase and %EEprot = 100% to the top phase), a complete downstream process was developed and implemented, in which the isolation of the target biomolecules (proteins, arabinose- and glucose-rich polysaccharides) and the reuse of the phase formers and main solvents applied was considered. In summary, the approach proposed using IL-ABS appears as a simple and efficient method of purification easily integrated into continuous flow processes, thus demonstrating its industrial potential.