Influence of pH Value and Ionic Liquids on the Solubility of l-Alanine and l-Glutamic Acid in Aqueous Solutions at 30 °C

Abstract

The solubility of the amino acids L-alanine and L-glutamic acid and its sodium salt (sodium L-glutamate monohydrate) in aqueous solutions at 30 °C and atmospheric pressure was investigated in the pH range between 3 and 9 and in the presence of the ionic liquids (ILs) 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([bmim][OTf]) and choline dihydrogencitrate ([ch][dhcit]) at pH 7. The solubility of L-alanine and L-glutamic acid in the solutions without IL was measured by UV spectroscopy and with a gravimetrical method. In the presence of an IL HPLC-analysis was applied. The solid phases were characterized using Raman spectroscopy and powder X-ray diffraction to distinguish the amino acids from their salts. While the solubility of L-alanine did not depend on pH within the considered pH range, the solubility of L-glutamic acid strongly increased with increasing pH. Below pH 6.2 the solid phase was characterized to be L-glutamic acid, while sodium L-glutamate monohydrate was found to be the solid at pH higher than 6.2. It could be observed that the solubility of sodium L-glutamate monohydrate was comparatively high, and increased with increasing pH. Upon addition of the ILs under investigation ([bmim][OTf]) and [ch][dhcit]) the solubility of L-alanine and L-glutamic acid was decreased. Original PC-SAFT was applied to predict the solubility of L-alanine and L-glutamic acid (and its sodium salt) in water, with and without the ILs under consideration, at the experimental conditions with quantitative agreement to the experimental data.

Extractivein situproduct removal for the application of naturally producedl-alanine as an amine donor in enzymatic metaraminol production

“…For simplicity, only pure substances were investigated at different pH values in the range of 7 -10.5. The experiments show that Lalanine and pyruvate could not be extracted into the 1-decanol phase at any pH (not shown), which is in line with comparable investigations 21,29 For metaraminol (figure 6) and (R)-3-OH-PAC (figure 7), a pH dependent phase distribution could be observed.…”

“…Hence, alternative methods for a robust, efficient, and scalable product recovery are sought. One such alternative method is liquid-liquid extraction (LLE), which was already shown to be applicable to some enzymatic systems 21 . In this contribution, we show that the integration of in-situ LLE in the biocatalytic production of metaraminol allows for enhanced process productivity when an amine donor from renewable resources is applied.…”

Melting properties of peptides and their solubility in water. Part 1: dipeptides based on glycine or alanine

“…It has been shown that in comparison to other models, PC-SAFT provides accurate modeling results of activity coefficients and prediction of solubility even in complex mixtures. [12][13][14][15] Thermodynamic models make use of an equilibrium condition between the solid dipeptide and the dipeptide in the saturated liquid phase. No mixed solids (pure compound in single solid phase) were assumed.…”

Determination of Nucleation Kinetics of Cephradine in 0.5% Sodium Bisulfate (W/V) Solution

“…The temperature was controlled to an accuracy of ±0.05 K by circulating water from a water bath. The mass was determined using an electronic analytical balance with an accuracy of ±0.0001 g, and a magnetic stirrer was used to accelerate the dissolution of the cephradine . A laser monitoring system, comprising a laser generator, laser power meter, and photoelectric transformer, was used to detect the saturation point, by observing the change in the intensity of the laser beam entering the solution .…”