Synergistically enhanced stability of laccase immobilized on synthesized silver nanoparticles with water-soluble polymers

"In Press, Accepted Manuscript, Available online 12 March 2017"Silver nanoparticles (AgNPs) were synthesized by citrate reduction method in the presence of polymers, poly(ethylene glycol) (PEG), poly(vinyl alcohol) (PVA) and chitosan, used as stabilizing agents, and an oxidoreductase enzyme, laccase (Lac), with the goal of expanding the NPs antimicrobial action. AgNPs were characterized by UV-visible spectrometry, dynamic light scattering and transmission electron microscopy. As protecting agents, PEG and PVA promoted the formation of spherical uniformly-shaped, small-sized, monodispersed AgNPs (≈ 20 nm). High Mw polymers were established as most effective in producing small-sized NPs. Chitosan's viscosity led to the formation of aggregates. Despite the decrease in Lac activity registered for the hybrid formulation, AgNPs-polymer-Lac, a significant augment in stability over time (up to 13 days, at 50 °C) was observed. This novel formulation displays improved synergistic performance over AgNPs-Lac or polymer-Lac conjugates, since in the former the Lac activity becomes residual at the end of 3 days. By enabling many ionic interactions, chitosan restricted the mass transfer between Lac and substrate and, thus, inhibited the enzymatic activity. These hybrid nanocomposites made up of inorganic NPs, organic polymers and immobilized antimicrobial oxidoreductive enzymes represent a new class of materials with improved synergistic performance. Moreover, the Lac and the AgNPs different antimicrobial action, both in time and mechanism, may also constitute a new alternative to reduce the probability of developing resistance-associated mutations.This work was funded by Portuguese Foundation for Science and TechnologyFCT/MCTES (PIDDAC) and co-financed by European funds (FEDER) through the PT2020 program, research projectM-ERA-NET/0006/2014. A. Zille and H. P. Felgueiras also acknowledge funding from FCT within the scope of the project POCI-01-0145-FEDER-007136 and UID/CTM/00264

Enzymatic polymerization on the surface of functionalized cellulose fibers

Enzymatic coating of functionalized cellulose fibers with catechol was performed in the presence of Trametes hirsuta laccase. Cellulose functionalization was done by covalent fixation of aromatic amines onto the cellulose surface using a dyeing procedure with C.I. Reactive Black 5 (RB5) followed by reduction with sodium hydrosulfite. Cellulase enzymes were used on coated and control samples to obtain the analytes linked with the soluble sugars in solution, to prove the reaction concepts described in this paper. Hydrolyzed coated-cellulose showed lower concentration of reducing sugars (1188 mg/L) than control samples (2011 mg/L). The structures of these compounds were checked by LC/MS analysis confirming the presence of functionalized glucose and cellobiose units coupled to poly(catechol) molecules (m/z 580 and m/z 633). Alkali extraction method showed to be very promising to coat cellulose fibers with phenols in the presence of enzymes, at mild conditions of temperature and pH

Laccase kinetics of degradation and coupling reactions

The ability of Trametes villosa laccase to degrade an azo dye (methyl orange) and to catalyze the coupling reactions between the aromatic amines and catechol was studied. It was found that the apparent Michaelis–Menten constants obtained from amperometric measurements were comparable to the ones obtained in the oxygen consumption experiments (8.20 and 7.40 µM, respectively). From the measurements of the mediated and mediatorless currents of azo dye degradation and coupling reactions itwas concluded that the addition of 1-hydroxybenzotriazole (HBT) as mediator considerably improves the catalytic efficiencies. It can be concluded that the mediated coupling of the aromatic amine with catechol opens the perspectives of physical removal of these polluting chemicals from the nature and the usage of the laccase immobilized onto macro-electrodes in online systems with continuous monitoring of the enzyme activity

Laccase polymerization of amino-phenol compounds

Abstracts of Papers of the American Chemical Society, 229, POLY331, U955-U955, 2005

Immobilized laccase for decolourization of Reactive Black 5 dyeing effluents

enzyme (194 h free and 79 h immobilized) depended on the dyeing liquor composition and the chemical structure of the dye. In the decolourization experiments with immobilized laccase, two phenomenons were observed – decolourization due to adsorption on the support (79%) and dye degradation due to the enzyme action (4%). Dyeing in the enzymatically recycled effluent provided consistency of the colour with both bright and dark dyes

Effects of base fabric parameters on the electro-mechanical behavior of piezoresistive knitted sensors

Strain sensors embedded into fabric structure are one of the most interesting research areas for health and engineering monitoring. In this paper, a textile-based strain sensor has been developed using an intrinsically conductive stainless steel-polyester plain knitted fabric. The influence of fabric structural parameters, such as loop length on electromechanical properties of sensors was studied under a tensile fatigue set. Knitted fabric structure deformation during tensile fatigue was monitored and image processed. Peak fitting of electric resistant waveforms (ERWs) and tensile fatigue versus time were performed to analyze the ERWs behavior in detail wherein the entire elongation of knit strain sensor partitioned into two distinct phases, such as loop head and loop leg sections. The results evidenced a discrepancy between loop head and loop leg elongation rate at the stretching onset and end of relaxing phase. The ERW with the higher resolution was obtained using the longest loop length along with the higher extension.This work was supported in part by FEDER through the COMPETE Program and in part by national funds through Portuguese Foundation for Science and Technology (FCT) under Project POCI-01-0145-FEDER- 007136 and Project UID/CTM/00264. The work of S. D. Tohidi was supported by the FCT under Grant SFRH/BD/94759/2013. The work of A. Zille was supported by FCT under Contract IF/00071/2015. The associate editor coordinating the review of this paper and approving it for publication was Prof. Tarikul Islam.info:eu-repo/semantics/publishedVersio