Xuerong Fan

Decolorization of reactive dyes by laccase immobilized in alginate/gelatin blent with PEG

To achieve effective decolorization of reactive dyes, laccase immobilization was investigated. Laccase 0.2% (m/V) (Denilite IIS) was trapped in beads of alginate/gelatin blent with polyethylene glycol (PEG), and then the supporters were activated by cross-linking with glutaraldehyde. The results of repeated batch decolorization showed that gelatin and appropriate concentration of glutaraldehyde accelerated the decolorization of Reactive Red B-3BF (RRB); PEG had a positive effect on enzyme stability and led to an increase of color removal. While the beads contained 0.2%, 2.0%, 2.0%, and 0.5% (m/V) of laccase, alginate, gelatin, and PEG, respectively. The dye of 50 mg/L initial concentration of RRB was decolorized down to 50% during the tenth repeated batch. As far as the decolorization mechanism was concerned, the thermal and pH stabilities of the immobilized laccase were also investigated and were both appreciably improved. The study indicates that the immobilized laccase can be potential candidate for utilization in biodecolorization processes.

Influence of combined enzymatic treatment on one-bath scouring of cotton knitted fabrics

The scouring of cotton knitted fabrics with alkaline pectinase, neutral cellulase, neutral–alkaline protease, and alkaline xylanase and mixtures thereof, in one bath was studied. The effects of enzyme combinations were studied against the criteria of wettability, burst strength loss and whiteness. The best combinations were (1) pectinase (4 g L−1) and cellulase (0.5 g L−1), (2) pectinase (4 g L−1), cellulase (0.5 g L−1) and protease (1 g L−1), (3) pectinase (4 g L−1), cellulase (0.5 g L−1) and xylanase (2 g L−1). The results showed that the scouring effects of enzyme mixtures were better than those of individual enzymes, and dyeing properties (K/S, colour parameters and colour fastness) of bioscoured cotton knits were comparable to those of conventionally alkaline scoured cotton knits.

Hydrophobic surface functionalization of lignocellulosic jute fabrics by enzymatic grafting of octadecylamine

Enzymatic grafting of synthetic molecules onto lignins provides a mild and eco-friendly alternative for the functionalization of lignocellulosic materials. In this study, laccase-mediated grafting of octadecylamine (OA) onto lignin-rich jute fabrics was investigated for enhancing the surface hydrophobicity. First, the lignins in jute fabrics were isolated and analyzed in the macromolecular level by MALDI-TOF MS, (1)H NMR, (13)C NMR, and HSQC-NMR. Then, the surface of jute fabrics was characterized by FT-IR, XPS, and SEM. Subsequently, the nitrogen content of jute fabrics was determined by the micro-Kjeldahl method, and the grafting percentage (Gp) and grafting efficiency (GE) of the enzymatic reaction were calculated. Finally, the surface hydrophobicity of the jute fabrics was estimated by contact angle and wetting time measurements. The results indicate that the OA monomers were successfully grafted onto the lignin moieties on the jute fiber surface by laccase with Gp and GE values of 0.712% and 10.571%, respectively. Moreover, the modified jute fabrics via OA-grafting showed an increased wetting time of 18.5 min and a contact angle of 116.72°, indicating that the surface hydrophobicity of the jute fabrics increased after the enzymatic grafting modification with hydrophobic OA molecules.

Modification of Bombyx mori silk fabrics by tyrosinase‐catalyzed grafting of chitosan

Tyrosinase could oxidize tyrosyl residues in silk fibroin and result in the production of activated o‐quinone residues, which could facilitate the grafting of the functional amino‐compounds onto silk fibers. In this study, the enzymatic modifications of Bombyx mori silk fibroin with tyrosinase and chitosan were investigated, aiming at improving the properties of silk fabrics, including dyeability, crinkling resistance, and antibacterial activity. The grafting grades of chitosan were evaluated by a color‐development method using bromocresol green. The result indicated that chitosan molecules were not only adsorbed on silk fibers via electrostatic interactions, they also could react with the oxidized silk fibers with tyrosinase. For the silk fabric combinedly treated with tyrosinase and chitosan, tensile strength and crinkling resistance were noticeably increased as compared to that of the chitosan‐treated. The antibacterial activity and its durability measurements revealed the actions of the tyrosinase‐catalyzed grafting of chitosan. The efficacy of the graft reaction might be further enhanced by increasing the accessibility of reactive sites in silk fibers.

Immobilization of catalase on cotton fabric oxidized by sodium periodate

Cotton fabric was first oxidized with sodium periodate, and then employed to immobilize catalase. Optimization studies for oxidation of the fabric and immobilization of the enzyme were performed. The properties of the immobilized catalase were examined and compared with those of the free enzyme. A high activity of the immobilized enzyme was obtained when the fabric was oxidized at 40°C and pH 6.0 for 8h in a bath containing 0.20 mol L−1 sodium periodate and the enzyme was immobilized at 4°C for 24h with a catalase dosage of 120.0 U mL−1. The immobilized enzyme exhibited optimum activity at 40°C, while the free enzyme had optimal temperature of 30°C, suggesting that the immobilized catalase could be used in a broader temperature range. Both the immobilized and free enzyme had pH optima of 7.0. The staining test and reusability showed that the catalase was fixed covalently on the oxidized cotton fabric.

Synthesis and characterization of starch-poly(methyl acrylate) graft copolymers using horseradish peroxidase

Horseradish peroxidase (HRP)-mediated graft polymerization in the presence of hydrogen peroxide (H2O2) and acetylacetone (Acac) has been successfully applied to the synthesis of starch-poly(methyl acrylate) (PMA). The graft copolymer was characterized by Fourier transform infrared (FT-IR), elemental analysis, nuclear magnetic resonance ((1)H NMR and (13)C NMR), and differential scanning calorimetry (DSC). FT-IR, elemental analysis and NMR confirmed that methyl acrylate (MA) was grafted onto starch successfully. DSC results showed the graft reaction had changed the crystalline regions of the gelatinized starch. The effects of pH, MA content, HRP dosage, incubation temperature and time on grafting percentage (GP) and grafting efficiency (GE) were also investigated. The GP and GE under optimal conditions reached 30.21% and 45.13%, respectively.

Transglutaminase‐modified wool keratin film and its potential application in tissue engineering

Transglutaminase (TGase) catalyzes the cross‐linking of many proteins and has been widely used to improve the properties of certain protein‐based materials. Keratin is considered as a promising biomaterial candidate following traditional chemical modification. In this study, the effect of TGase on the properties of a wool keratin film was investigated. The TGase‐modified film was applied to drug release and cell proliferation. Treatment with TGase (30 U/g keratin) for 18 h at 40°C increased the tensile strength of the film from 5.18 ± 0.15 MPa to 6.22 ± 0.11 MPa and decreased the elongation at break from 83.47 ± 1.79% to 72.12 ± 3.02%. The stability of the film in PBS and in artificial gastric juice was also improved. A rougher surface and a more compact cross‐section were observed by scanning electron microscopy photographs of the TGase‐treated film. SDS‐PAGE analysis confirmed that higher molecular weight proteins were formed in the TGase‐modified keratin solution and film. The results of the drug release assay using diclofenac indicated that both films with and without TGase treatment led to a high initial release in PBS, which was more constant in artificial gastric juice. The enzyme treatment led to a lower drug release rate from the film. Cell culture experiments suggested that the TGase‐mediated cross‐linked keratin film shows a good biocompatibility and that it can be used for tissue engineering applications.

Cellulase immobilization onto the reversibly soluble methacrylate copolymer for denim washing

Cellulase treatment of denim fabrics is an environmentally friendly way for producing desired worn look. In this work, the enzymatic treatments of the denim fabrics, i.e., bio-washing, using native cellulase and cellulase immobilized with reversibly soluble copolymer (Eudragit S-100), immobilized-cellulase, have been investigated. According to the analyses of the lightness (CIE L value), color strength (K/S value) and color variations, at a cellulase concentration level of 6% o.w.f., the denim fabrics treated with the immobilized cellulase showed decoloration and color effect close to the native cellulase. However, the immobilized cellulase treatment of the denim fabrics showed lower weight loss and considerably higher tensile strength than those treated with the native cellulase. Both the native and immobilized cellulases improved the crystalline indice and the apparent crystallite size of the fiber sample compared with the control ones. The amorphous portion of the cellulose suffered more hydrolysis by the native cellulase than the immobilized cellulase. Scanning electron microscope pictures (SEM) and digital pictures further indicated that the immobilized cellulase can efficiently remove indigo dyestuffs on the surfaces of the denim fabrics without the problem of excessive damage to the fibers.

Hydrophobic modification of cotton fabric with octadecylamine via laccase/TEMPO mediated grafting.

Hydrophobic cotton fabrics were prepared by grafting octadecylamine (ODA) onto cotton fiber surfaces via the laccase/2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) treatment. The cotton fibers were oxidized by laccase/TEMPO to introduce aldehyde groups, which reacted with the amino groups of ODA to form Schiff base. First, ODA was coupled to glucan, used as a model compound of cellulose. The results of FT-IR and MALDI-TOF mass spectroscopy prove the formation of a Schiff base between ODA and glucan. Moreover, the existence of ODA in the grafted cotton fibers was verified by ATR-FTIR, elemental analysis, X-ray photoelectron spectroscopy. Finally, the hydrophobicity of the ODA-grafted cotton fabrics was estimated. The surface hydrophobicity of the cotton fabrics increased after the enzymatic grafting reaction.

Conductive cotton prepared by polyaniline in situ polymerization using laccase

The high-redox-potential catalyst laccase, isolated from Aspergillus, was first used as a biocatalyst in the oxidative polymerization of water-soluble conductive polyaniline, and then conductive cotton was prepared by in situ polymerization under the same conditions. The polymerization of aniline was performed in a water dispersion of sodium dodecylbenzenesulfonate (SDBS) micellar solution with atmospheric oxygen serving as the oxidizing agent. This method is ecologically clean and permits a greater degree of control over the kinetics of the reaction. The conditions for polyaniline synthesis were optimized. Characterizations of the conducting polyaniline and cotton were carried out using Fourier transform infrared spectroscopy, UV–vis spectroscopy, cyclic voltammetry, the fabric induction electrostatic tester, and the far-field EMC shielding effectiveness test fixture.