Measurement and modelling solubility of amino acids and peptides in aqueous 2-propanol solutions.

Hoang Tam Do,Christoph Held,Marcel Klinksiek,Sophia Volpert,Max Thome,Patrick Franke

doi:10.1039/d1cp00005e

Abstract

Amino acids and peptides are essential components in the biochemical industry. The final products are employed in a wide range of applications and are often synthesized by fermentation and purified in a complex downstream process. One possible separation step is using an additional solvent to lower the solubility of the desired product and, thus, promote the crystallization of the particular component. Therefore, it is crucial to have accurate knowledge of the solubility of these components. In this work, the solubilities of 20 proteinogenic amino acids and 21 peptides in aqueous 2-propanol solutions were gravimetrically determined. Additionally, the pH values of the saturated liquid phases were measured and the crystal structures of solid crystals were analysed using X-ray diffraction. The anti-solvent 2-propanol caused a decrease in the solubilities of the amino acids and peptides upon increasing its mass fraction. Exceptions were found for amino acids with aromatic substituents, l-phenylalanine and l-tyrosine. The solubility of 15 amino acids and 18 peptides was successfully modelled using the equation of state PC-SAFT that used recently determined melting properties of the amino acids and peptides as input data.

Highlights

Amino acids and peptides are essential biomolecules in the body, and attract increasing attention in the chemical industry and biotechnology.[1,2] This is mainly due to the wide range of applications of amino acids and their derived products
Proteinogenic amino acids and peptides investigated in this work are listed in Table S1 in the ESI.† All components were of commercial grade and used without additional purification
The dissociation constants of amino acids in aqueous 2-propanol solutions have already been investigated by Dey et al.[26]

Summary

Introduction

Amino acids and peptides are essential biomolecules in the body, and attract increasing attention in the chemical industry and biotechnology.[1,2] This is mainly due to the wide range of applications of amino acids and their derived products. One possible method for separating amino acids or peptides from other biomolecules or industrial residues is the so-called anti-solvent crystallization. An additional solvent, like ethanol or 2-propanol, can be utilized to lower the total solubility to promote the crystallization of the particular component.[5] This technique is favourable because extreme process conditions (e.g., high or low temperature, high shear forces, or high pressures) can be avoided, and the biomolecules can be purified more gently

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Conclusion