Biocatalytic Syntheis of L‐Pipecolic Acid by a Lysine Cyclodeaminase: Batch and Flow Reactors

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+.