Biocatalytic Synthesis of l‐Pipecolic Acid by a Lysine Cyclodeaminase: Batch and Flow Reactors

Abstract l ‐Pipecolic Acid ( l ‐PA) is a valuable building block for the synthesis of pharmaceuticals such as anesthetics and immunosuppressants. Thus, more efficient and greener strategies are desired for its production. Herein, we have applied a previously engineered variant of the Lysine Cyclodeaminase from Streptomyces pristinaespiralis (e‐SpLCD) for the bioconversion of l ‐Lysine into l ‐PA. The reaction can be performed by the free e‐SpLCD reaching full conversion to 50 mM l ‐PA. From a biotechnological perspective, the process scale‐up has been trialed in a SpinChem® reactor, albeit with lower conversion yields. To further enhance the biocatalyst stability, we present a detailed study of the e‐SpLCD immobilization on microparticles. This enabled the integration of the immobilized biocatalyst into a packed‐bed reactor for the continuous flow synthesis of l ‐PA. The full conversion was achieved in 90 min, maintaining also high operational stability. Remarkably, the addition of exogenous cofactor was not needed for the flow reaction, although the long‐term operational stability was improved by the addition of NAD + .