Selective Recovery of L-pipecolic Acid from L-lysine Bioconversion Mixture by Liquid-liquid Extraction

L-pipecolic acid (L-PA) is a key chiral intermediate in the synthesis of many important drugs. However, there is a lack of research on the efficient extraction and purification process for L-PA. Here, eleven different organic solvents were evaluated for selective extraction of L-PA by physical extraction. Among these solvents, methyl ethyl ketone (MEK) showed the highest extraction yield of L-PA, and analysis of the linear solvation energy relationship between the solvents showed that MEK was the most suitable solvent for L-PA extraction. The highest extraction yield of L-PA was 37% under optimal conditions (pH 6, 20°C, 30 min and ratio of 1). Furthermore, the repetitive extraction of L-PA from bioconversion solution was also investigated. The MEK gave high purity of L-PA (93.1% and 22.8% yield) from the bioconversion mixture. Our study is the first approach to show easy recovery of L-PA by liquid-liquid extraction and the application of MEK extraction method to L-lysine bioconversion mixture.