Partitioning of Riboflavin in Sustainable Aqueous Biphasic Systems and the Influence of Solubility

Developing sustainable extraction techniques for the recovery of bioactive substances from biowaste is key toward promoting a circular economy and reducing the environmental impact in industrial processes. This work employs aqueous biphasic systems (ABSs) based on ethyl lactate (EL), water, and organic salts (Na2Tartrate, NaKTartrate, and K3Citrate) for the extraction of riboflavin (B2), a vitamin commonly found in biowaste. B2 partitioning, evaluated through the partition coefficient (K) and extraction efficiency (E), was deemed successful for all ABSs, with the Na2Tartrate-based ABS presenting the best results, yielding K = 8.23 ± 0.07 and E = (87.5 ± 0.8)% for the longest tie-line. Published data on chlorogenic acid (CA) were used for comparison, with CA showing similar partitioning trends but consistently higher performance. To assess this difference, solubility studies were conducted for both biomolecules at 283.15, 298.15, and 313.15 K. The solubility of both species in EL was higher than in water, supporting the preferential partition to the top phase. Moreover, CA presented a higher solubility in EL than B2, which is consistent with its superior partition results. Last, the van't Hoff equation was applied to the solubility data, though the solubility of B2 in EL did not align with this model.