Immobilization of Phenylalanine Ammonia‐Lyase on Single‐Walled Carbon Nanotubes for Stereoselective Biotransformations in Batch and Continuous‐Flow Modes

摘要

Carboxylated single‐walled carbon nanotubes (SwCNTCOOH) were used as a support for the covalent immobilization of phenylalanine ammonia‐lyase (PAL) from parsley by two different methods. The nanostructured biocatalysts (SwCNTCOOH‐PAL^I and SwCNTCOOH‐PAL^II) with low diffusional limitation were tested in the batch‐mode kinetic resolution of racemic 2‐amino‐3‐(thiophen‐2‐yl)propanoic acid (>1) to yield a mixture of (R)‐>1 and (E)‐3‐(thiophen‐2‐yl)acrylic acid (>2) and in ammonia addition to >2 to yield enantiopure (S)‐>1. SwCNTCOOH‐PAL^II was a stable biocatalyst (>90 % of the original activity remained after six cycles with >1 and after three cycles in 6 m NH3 with >2). The study of ammonia addition to >2 in a continuous‐flow microreactor filled with SwCNTCOOH‐PAL^II (2 m NH3, pH 10.0, 15 bar) between 30–80 °C indicated no significant loss of activity over 72 h up to 60 °C. SwCNTCOOH‐PAL^II in the continuous‐flow system at 30 °C was more productive (specific reaction rate, r flow=2.39 μmol min⁻¹ g⁻¹) than in the batch reaction (r batch=1.34 μmol min⁻¹ g⁻¹).