Influence of inorganic impurities in fermentation broth on the crystallization mechanism of co-produced bio-based cadaverine succinate: Experimental and molecular simulations

Impurity sulfate produced in upstream process of nylon 54 salt (cadaverine succinate) are significantly impacting the product quality. In the present study, we elucidated the mechanism underlying the crystallization of the nylon 54 salt; using sulfate ions as the only inorganic impurity before crystallized nylon 54 salt, we revealed the principles underlying their impact. Specifically, sulfate ions profoundly affect the thermodynamics and kinetics of nylon 54 salt crystallization. The solubility of the monomer salt decreased. At 288.15K, the solid-liquid interfacial energy, critical nucleation radius, and Gibbs free energy increased 0.104mJ.m-2, 2.890×10-10 m, and 9.668×10-22 J respectively. The increased nucleation barrier further hinders the crystallization of nylon 54 salt. Molecular dynamics simulations reveal that sulfate impurities reduce molecular diffusion, enhance hydrogen bond formation, increase intermolecular and overall interaction energy. Thus, our study provides valuable insights into the one-step separation of bio-based cadaverine and succinic acid in a coproduction system.