Supersaturation control using membrane-assisted anti-solvent crystallization

Chergaoui, Sara [UCL] Leyssens, Tom [UCL] Debecker, Damien P. [UCL] Luis Alconero, Patricia [UCL] et al.

Hydrophobic porous polymeric membranes were studied for the antisolvant crystallization of L-serine, an amino acid that has great significance in agro- and pharma- industries. Its synthesis involves fermentation, recovery and purification with antisolvant crystallization which evokes concerns regarding organic impurities. The impact of the pressure, antisolvent composition, flow rate, temperature and batching time were investigated in the variation of supersaturation hence the crystal characteristics of L-serine using water as solvent and ethanol as antisolvant. Preliminary findings using PVDF membranes with a pore size of 0.22 μm, suggest that an increase in the flow rate ratio of the anti-solvant to crystallizing solution stimulates crystal growth in shorter elaped time indicating the low level of supersaturation. The latter is commonly expressed as the ratio of the solution concentration and its concentration at saturation (c/c*), and it is the fundamental driving force of crystallization. The trade between nuclearion and growth reflects directly on the crystal morphology such that larger and fewer crystals were observed forming at a flow rate ratio of 1:1 compared to 3:1. The ability of the membrane-based crystallization (MCr) to tune the various above-mentioned parameters leads to a controlled crystal nucleation and growth of L-serine in a more sustainable and energy-intensive way. On top of that, MCr could produce L-serine crystals with higher purity (minimal trapped organic impurities) while maintaining a low supersaturation level.