Effects of Structure Similar Additive on the Crystallization of L-Phenylalanine from Aqueous Solution

Abstract

A comprehensive understanding of the effect of structure similar additives on the nucleation and growth of amino acid in aqueous solution is of great significance for the crystallization of L-phenylalanine and industrial production of anhydrous L-phenylalanine. This paper mainly focuses on the influence of L-tyrosine on the crystallization process of L-phenylalanine by investigating the variation and typical phenomenon in solubility, metastable zone width, crystal nucleation and growth process, and crystal morphology. The results show that the existence of L-tyrosine can obviously increase the solubility and narrow the metastable zone of L-phenylalanine thus promote the nucleation process. Meanwhile, L-tyrosine can also selectively inhibit the formation of monohydrate and improve the purity of industry-favored anhydrous L-phenylalanine in the final product. In order to explore the inhibiting effect of L-tyrosine in crystallization process, the molecular configurations in two different crystallization states were simulated by using Molecular Dynamics.The results show that water and L-phenylalanine molecules tend to form anhydrous crystals when the addition proportion of L-tyrosine increases. The theoretical calculations are in good agreement with the experimental data. The conclusions of this paper will provide new ideas and effective controlling approaches for L-phenylalanine crystals’ morphology and amino acids’ crystallization process.