- A novel strategy for efficient chemoenzymatic synthesis of D-glutamine using recombinant Escherichia coli cells
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D-glutamine is a D type stereoisomer of glutamine which is involved in many metabolic processes. Seeking lower-cost and industrially scalable approaches for the synthesis of D-glutamine is very valuable both in academic career and potential applications. Herein, we developed a novel efficient chemoenzymatic strategy for producing D-glutamine. Initially, DL-glutamine was chemically prepared with cheap and accessible DL-glutamic acid as raw material. Subsequently, the L-glutamine among the racemic mixture was selectively hydrolyzed to L-glutamic acid by Escherichia coli whole-cell system which expressed L-aminopeptidase D-Ala-esterase/amidase (DmpA) from Ochrobactrum anthropi. The left D-glutamine was obtained by isoelectric point precipitation with 70% of the theoretical yield. Furthermore, we optimized enzymatic resolution conditions to determine the optimum parameters as pH 8, 30 °C, 0.1% (v/v) Triton X-100, and 1 mM Mn2+. These results suggested that our strategy might be potentially usable for the synthesis of D-glutamine in industrial productions.
- Du, Qinglin,Zhang, Xiangyang,Pan, Xinru,Zhang, Hongjuan,Yang, Yu-Shun,Liu, Junzhong,Jiao, Qingcai
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- Chiral Recognition of Natural Products on Optically Active Polysiloxanes
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Polysiloxanes with chiral peptide side chains have been synthesized and used as stationary phases in gas chromatography.With these phases amino acid enantiomers can be separated as N-acyl esters.Due to temperature stability up to 230 deg C all protein amino acids can be separated and the racemization of synthetic biologically active peptides controlled.The phases can be used to assign the absolute configuration of amino acids.A variety of other classes of compounds can be separated into their enantiomers using the chiral polysiloxanes, like hydroxy acids, sulfoxides, phosphorous compounds, glycols, atrop isomers, amines and alcohols.Various applications of these phases are described including investigations of enantiomer selectivity in nature. - Key words: Polysiloxanes, Enantiomers, Racemization
- Bayer, Ernst
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p. 1281 - 1291
(2007/10/02)
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- Process for obtaining amino acids from the raw juices of sugar manufacture
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To recover amino acids from raw sugar juice, as obtained in beet extraction, the juice is treated with acid or with lime to coagulate impurities which are separated off. The juice may be treated before or after coagulation with a pectin-cleaving enzyme. The juice so pretreated can be directly passed through a strong cation exchanger and a weak anion exchanger whereby the amino acids are adsorbed. Switchover to a new cation exchanger is initiated when betaine flows out the column. Elution is effected, preferably with an ammonium compound, and eluate is collected, preferably each fraction being enriched in a different amino acid. The sugar juice may be concentrated and crystallized in known manner and is of comparatively high purity.
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