Separation of L‐aspartic acid and L‐glutamic acid mixtures for use in the production of bio‐based chemicals

Abstract

BACKGROUND: Amino acids are promising feedstocks for the chemical industry due to their chemical functionality. They can be obtained by the hydrolysis of potentially inexpensive protein streams such as the byproduct of biofuel production. However, individual amino acids are required before they can be used for the further production of chemicals. Here, the separation of L‐aspartic acid (Asp) and L‐glutamic acid (Glu) mixture, which can be isolated from protein hydrolysis solutions at low pH or from electrodialysis of complex amino acid mixtures, was studied.RESULTS: Glu was converted into L‐pyroglutamic acid (pGlu) which can be separated from the mixture of Asp and Glu due to its higher solubility in water. The conversion was carried out under aqueous or melt conditions. Under aqueous conditions, the conversion was studied as a factor of time, temperature and the amount of Glu. The conversion was specific with high yield and not effected by Asp. After pGlu was separated from Asp and residual Glu by solubility difference, it can be transferred back to Glu through hydrolysis.CONCLUSION: The conversion of Glu to pGlu is specific and can be applied to separation Asp and Glu for their use in the production of bio‐based chemicals. Copyright © 2012 Society of Chemical Industry

Protein‐Rich Biomass Waste as a Resource for Future Biorefineries: State of the Art, Challenges, and Opportunities

“…Aspartic acid and asparagine can also be present in substantial amounts; for example, about 10 % in castor bean meal and soybean meal. Therefore, the acidic amino acid fraction has often been suggested to have the highest potential for the production of chemicals . Moreover, both glutamic acid and aspartic acid are non‐essential amino acids, hence, they will not compete with feed applications.…”

“…In the second step, this mixture was treated under dilute acidic conditions (e.g., 1 m HCl, 95 °C, 48 h) to induce profound peptide hydrolysis and glutamine deamidation, yielding about 70 % free glutamic acid and 10 % pyroglutamic acid, as a result of spontaneous intramolecular condensation of both glutamine and glutamic acid at higher temperature. The overall glutamic acid yield was increased to 80 % by hydrolyzing the lactam moiety in pyroglutamic acid under highly acidic or alkaline conditions . About 55 % of the total amino acid content was liberated in this two‐step procedure.…”

“…Excellent yields of pyroglutamic acid were obtained in aqueous solutions (86 %; 3 h at 120 °C) as well as in a melt (>99 %; 45 min at 150 °C) of both amino acids. Aspartic acid remained intact, because cyclization to the β‐lactam derivative is thermodynamically disfavored and deamination to fumaric acid is negligible under acidic conditions at 150 °C . Subsequently, aspartic acid can be separated with high purity by precipitation, owing to its low solubility in water compared to pyroglutamic acid (respectively 5.39 g L −1 and 476 g L −1 ).…”

“…Subsequently, aspartic acid can be separated with high purity by precipitation, owing to its low solubility in water compared to pyroglutamic acid (respectively 5.39 g L −1 and 476 g L −1 ). After subsequent hydrolysis of pyroglutamic acid in concentrated acid (e.g., 2 m H 2 SO 4 ), aspartic acid and glutamic acid were recovered with overall yields up to 80 % and 99 %, respectively An alternative approach involves a nonreversible modification or defunctionalization of one or more amino acids to valuable end products that are readily separated from each other or from unreacted amino acids.…”

Towards plant protein refinery: Review on protein extraction using alkali and potential enzymatic assistance

“…In the case of amino acids it is difficult to separate on size, and other methods have to be chosen. Electrodialysis can be used, if necessary combined with a conversion step [3, 4]. Another technique to be used is anti‐solvent crystallization (still under development).…”