Propanol - Sugar aqueous biphasic systems as a suitable platform for biomolecules extraction.

Aiming at designing efficient extraction processes, this work proposes the novel aqueous biphasic systems (ABS) composed of sugars and alcohols. The complete liquid-liquid phase diagrams (binodal curves and tie-lines) for several ternary systems of {water + 1-propanol / 2-propanol + sugar (mono- and di-saccharides, and their polyols)} were determined, for the first time. The main factors which affect the phase separation ability of these systems, such as temperature, structure and stereochemistry of sugars, and the alcohol type were discussed. In all the studied ABS, the top phase is alcohol-rich with lower water content, while the bottom phase is sugar-rich with higher water content. The partitioning behavior of two alkaloids (caffeine and codeine) and a flavoring antioxidant (vanillin) in the produced ABS was evaluated. In all the partitioning experiments, caffeine and vanillin have a preferable tendency to concentrate in the more hydrophobic alcohol-rich phase, however, codeine preferentially migrate to the more hydrophilic sugar-rich phase. The selectivity index of the alcohol-sugar ABS to separate compounds of the same family (caffeine and codeine) was calculated and found to be higher than 25 at optimum conditions. In general, the more soluting-out ability of sugars, the more difference in the water content of the coexisting phases, and the longer tie-line length lead to the better extraction performance of the propanol-sugar ABS. Heating has a favorable effect on the preferential partitioning of caffeine and codeine, but it is unfavorable for extraction of vanillin. From the results gathered, the novel ABS produced in this work provide efficient and money-saving extraction platforms, and can selectively separate similar biomolecules.