## 1 Introduction  
Lacase (\(p\)-diphenyl: dioxygen oxidoreductase, EC 1.10.3.2) belongs to the family of copper-containing oxidases, which catalyze the 1-electron oxidation of a wide range of inorganic and organic substances, coupled with a 4-electron reduction of oxygen to water [1; 2; 3; 4]. This enzyme is among the most studied redoxases and has been used successfully as a commercial industrial catalyst. Lacase (Lac) has shown many applications in biomedical, biotechnological, and environmental areas such as organic synthesis, wine cork making, teeth whitening, immunoassay analyte labeling, biofuel cells, and biosensors [4; 5; 6]. Moreover, Lac can also play a major role in bioremediation processes such as dye removal from wastewater [7; 8]. As is widely known, the difficulty of recovering free enzymes from solution and the poor stability of many free enzymes, including Lac, have hindered their development for use in large-scale applications [9]. Accordingly, immobilized enzymes have greater prospects for development since they have higher storage, thermal, and operational stabilities than their free counterparts. Among the carrier materials commonly used for immobilizing enzymes, nanomaterials have attracted great attention due to their large surface area to volume ratio and high porosity, which are highly efficient for enzyme attachment [10; 11]. More importantly, the development of various nanostructure carriers for enzyme immobilization facilitates a broader range of applications and an increased efficiencyof immobilized enzymes [12; 13; 14]. Furthermore, for some redoxases that require an electron shuttle for their catalytic reaction, their activity can be enhanced when these enzymes are immobilized on electron-conducting carriers. It has been demonstrated that carbon nanotubes are an ideal carrier for redoxase immobilization, since they possess superb electrical conductivity and can effectively enhance direct electron transfer between electrodes and proteins [15; 16]. In addition, magnetic polymer-based nanocomposites for enzyme immobilization have also attracted extensive attention since they have shown great potential for applications in enzyme recovery and recycling [10]. Since Lac is a redoxase, it has been speculated that its activity may be enhanced through an electron-transfer pathway between the carrier and the enzyme when it is immobilized on nanostructured materials with good conductivity. Polyaniline and poly(_p_-phenylenediamine) (_P_p_PD) nanofibers have a large surface area and a high density of nanopores onto which enzymes can be efficiently absorbed. These nanofibers are also capable of conducting electricity as polymer nanowires. Therefore, they are considered to be excellent candidate materials for enzyme immobilization, especially for redoxases. The use of magnetic and electron-conducting _P_p_PD nanofibers as supports for Lac immobilization has the following obvious advantages: (1) the high specific surface area and functional N-H groups of _P_p_PD nanofiber are suitable for the efficient binding of Lac; (2) magnetic nanocomposites provide a method for easily separating immobilized enzymes from solutions following treatment, thereby lowering operation costs; (3) conductive _P_p_PD nanofibers can provide efficient channels for electron transportation between enzymes and their substrates, which could improve the catalytic activity of Lac. A wide variety of dyes have been extensively used in many industries such as the pulp, leather, cosmetics, food, paper, and textile industries [17]. Synthetic dyes have harmful effects on the environment owing to their toxicity to microbes, hydrophytes, and animals. Thus, environmental protection acts have been enacted in most countries, which demand that textile waste must be treated before being released into natural water bodies [18]. It has now been proven that Lac can oxidize many synthetic dyes with high efficiency [19; 20].