Partition of spiramycin in a recyclable aqueous two-phase system based on pH-responsive and thermosensitive polymers

Effective extraction of tylosin and spiramycin from fermentation broth using thermo-responsive ethylene oxide/propylene oxide aqueous two-phase systems

Recyclable aqueous two-phase systems with thermo-responsive phase-forming materials have been employed to separate macromolecules; however, these systems have achieved very limited separation efficiency for small molecules, such as antibiotics. In this study, aqueous two-phase systems composed of the ethylene oxide/propylene oxide copolymer and water were developed to extract alkaline antibiotics from the fermentation broth. In the aqueous two-phase systems with an ethylene oxide ratio of 20 and propylene oxide ratio of 80, the partition coefficients of tylosin and spiramycin reached 16.87 and 20.39, respectively, while the extraction recoveries were 70.67 and 86.70%, respectively. Coupled with mechanism analysis, we demonstrated the feasibility of extracting alkaline antibiotics using this aqueous two-phase system, especially for 16-membered macrolide antibiotics. The molecular dynamic simulation was employed to visualize the process of dual-phase formation and the partition behavior of antibiotics in an aqueous two-phase system. The dynamic simulation revealed the binding energy between the antibiotic and ethylene oxide/propylene oxide copolymers, which provides a simple indicator for screening suitable antibiotics in aqueous two-phase systems. Our recyclable aqueous two-phase systems provide a robust approach for the extraction of 16-membered macrolide antibiotics with ease of operation and high recovery rates, which is appropriate for large-scale extraction in the fermentation industry.

Synthesis of Purine-Based Ionic Liquids and Their Applications

Bio-based ionic liquids (ILs) are being increasingly sought after, as they are more sustainable and eco-friendly. Purines are the most widely distributed, naturally occurring N-heterocycles, but their low water-solubility limits their application. In this work, four purines (theobromine, theophylline, xanthine, and uric acid) were combined with the cation tetrabutylammonium to synthesize bio-based ILs. The physico-chemical properties of the purine-based ILs were characterized, including their melting and decomposition temperatures and water-solubility. The ecotoxicity against the microalgae Raphidocelis subcapitata was also determined. The ILs show good thermal stability (>457 K) and an aqueous solubility enhancement ranging from 53- to 870-fold, in comparison to their respective purine percursors, unlocking new prospects for their application where aqueous solutions are demanded. The ecotoxicity of these ILs seems to be dominated by the cation, and it is similar to chloride-based IL, emphasizing that the use of natural anions does not necessarily translate to more benign ILs. The application of the novel ILs in the formation of aqueous biphasic systems (ABS), and as solubility enhancers, was also evaluated. The ILs were able to form ABS with sodium sulfate and tripotassium citrate salts. The development of thermoresponsive ABS, using sodium sulfate as a salting-out agent, was accomplished, with the ILs having different thermosensitivities. In addition, the purine-based ILs acted as solubility enhancers of ferulic acid in aqueous solution.

Enantioselective liquid-liquid extraction of tryptophan enantiomers by a recyclable aqueous biphasic system based on stimuli-responsive polymers

The hydrophobic organic solvents/water biphasic system had been always used in the traditional enantioselective liquid-liquid extraction (ELLE). In recent years, aqueous biphasic systems (ABSs) are considered as a promising method used in the ELLE. In the present work, a recyclable ABS composed of a temperature-responsive polymer poly(MAH-β-CD-co-NIPAAm) (P_N-CD) and a pH-responsive polymer poly(AA-DMAEMA-BMA) (P_ADB) was employed in the enantioseparation of tryptophan enantiomers. The polymer P_N-CD acted as not only the phase-forming component but also the chiral selector, which can be recycled by changing the temperature. The polymer P_ADB can be used as the phase-forming component, which can also be recycled by adjusting the pH. The phase behaviors of this P_N-CD/P_ADB ABS had been studied. The influencing parameters were studied for this chiral separation process, including the polymer concentration, initial tryptophan concentration, extraction temperature, and system pH. The maximum separation factor (α) of 1.42 was obtained by one-step extraction under the optimal conditions. Meanwhile, the distribution coefficients of L-tryptophan (L-Trp) and D-tryptophan (D-Trp) were 2.79 and 1.96, respectively. This study develops a green and sustainable strategy for enantioseparation by using the ELLE.

Partition of Tea Saponin with a Novel Recyclable Thermo-pH Aqueous Two-Phase Systems

Aqueous two-phase systems (ATPS) have the advantages of environmentally friendly, high mass transfer efficiency, and mild extraction conditions. However, it is difficult to recycle these polymers, which limits the large-scale application of ATPS. In this study, a novel recyclable ATPS was constructed with thermo-responsive polymer P_N and pH-responsive polymer P_ADB4.78 for the partition of tea saponin. P_N represents poly-(N-isopropylacrylamide), and P_ADB4.78 represents poly-(acrylic acid-dimethylamine ethyl methacrylate-butyl methacrylate), where 4.78 in the subscript indicate the isoelectric point of the polymer. The recoveries of P_N and P_ADB4.78 were 95.36% and 93.48%, respectively, after two cycles. Meanwhile, the phase formation mechanism of ATPS was studied by surface tension and low-field nuclear magnetic resonance (LF-NMR). The effects of polymer concentration, pH, temperature, types and concentrations of salt were investigated on tea saponin partition. In the 1.5% (w/v) P_N/3.5% (w/v) P_ADB4.78 ATPS, the optimal partition coefficient (K) of crude tea saponin were 0.15 in the presence of 1.5 mM KCl at pH 7.6 and 25 °C while the extraction recovery (ER_b) reached 92.13%. The K and ER_b of tea saponin from tea seeds were 0.12 and 94.50% with 7.5 mM LiBr at pH 8.0 and 25 °C, respectively.