Two-step enzymatic functionalisation of polyamide with phenolics

A two step enzymatic process for grafting phenolics onto polyamides (PAs) was developed in order to impart special functionalities to inert PA. Therefore, a polyamidase (NfpolyA) from Nocardia farcinica was overexpressed in Escherichia coli BL21-Gold(DE3) and purified in a single step. With p-nitroacetanilide as a substrate, NfpolyA revealed a specific activity of 20 U mg−1 compared to 1.5 U mg−1 for the wild-type enzyme. NfpolyA showed a KM value of 0.12 ± 0.01 mM and a kcat of 19.1 s−1 which were both higher than measured for the wild-type enzyme (kcat = 3.5 s−1; KM = 0.06 mM). A laccase from Trametes hirsuta was used to oxidize ferulic acid, used as a phenol model substrate and study the covalent grafting of n-butylamine, as model substrate for PA. According to LC–MS, up to three equivalents of n-butylamine were bound to ferulic acid after laccase oxidation of ferulic acid. Both enzymes were used sequentially in a two step process. In a first step the polyamidase is used to partially hydrolyze the amide bond, leading to a surface with amine and carboxylic acids. In a second step, by using a laccase from T. hirsuta ferulic acid was grafted onto the surface of PA as confirmed with FTIR-ATR analysis.