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

Abstract

Abstract Carboxylated single‐walled carbon nanotubes (SwCNT COOH ) were used as a support for the covalent immobilization of phenylalanine ammonia‐lyase (PAL) from parsley by two different methods. The nanostructured biocatalysts (SwCNT COOH ‐PAL I and SwCNT COOH ‐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 . SwCNT COOH ‐PAL II was a stable biocatalyst (>90 % of the original activity remained after six cycles with 1 and after three cycles in 6 M NH 3 with 2 ). The study of ammonia addition to 2 in a continuous‐flow microreactor filled with SwCNT COOH ‐PAL II (2 M NH 3 , pH 10.0, 15 bar) between 30–80 °C indicated no significant loss of activity over 72 h up to 60 °C. SwCNT COOH ‐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 ).