scholarly journals Biocatalytic Strategy for Grafting Natural Lignin with Aniline

Molecules ◽  
2020 ◽  
Vol 25 (21) ◽  
pp. 4921
Author(s):  
Sabina Gabriela Ion ◽  
Teodor Brudiu ◽  
Anamaria Hanganu ◽  
Florentina Munteanu ◽  
Madalin Enache ◽  
...  
Keyword(s):  
Gel Permeation Chromatography ◽  
Industrial Applications ◽  
Enzyme Concentration ◽  
Radical Mechanism ◽  
Polymeric Product ◽  
Oh Groups ◽  
Before And After ◽  
Peroxidase Enzyme ◽  
Amine Groups ◽  
Temperature Programmed

This paper presents an enzyme biocatalytic method for grafting lignin (grafting bioprocess) with aniline, leading to an amino-derivatized polymeric product with modified properties (e.g., conductivity, acidity/basicity, thermostability and amino-functionalization). Peroxidase enzyme was used as a biocatalyst and H2O2 was used as an oxidation reagent, while the oxidative insertion of aniline into the lignin structure followed a radical mechanism specific for the peroxidase enzyme. The grafting bioprocess was tested in different configurations by varying the source of peroxidase, enzyme concentration and type of lignin. Its performance was evaluated in terms of aniline conversion calculated based on UV-vis analysis. The insertion of amine groups was checked by 1H-NMR technique, where NH protons were detected in the range of 5.01–4.99 ppm. The FTIR spectra, collected before and after the grafting bioprocess, gave evidence for the lignin modification. Finally, the abundance of grafted amine groups was correlated with the decrease of the free –OH groups (from 0.030 to 0.009 –OH groups/L for initial and grafted lignin, respectively). Additionally, the grafted lignin was characterized using conductivity measurements, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), temperature-programmed desorption (TPD-NH3/CO2) and scanning electron microscopy (SEM) analyses. The investigated properties of the developed lignopolymer demonstrated its disposability for specific industrial applications of derivatized lignin.

scholarly journals Enzyme kinetics and metabolic control. A method to test and quantify the effect of enzymic properties on metabolic variables

1990 ◽  
Vol 269 (3) ◽  
pp. 697-707 ◽  
Author(s):  
L Acerenza ◽  
H Kacser
Keyword(s):  
Enzyme Concentration ◽  
Time Dependent ◽  
Experimental Systems ◽  
State Approximation ◽  
Metabolic Systems ◽  
Steady State Approximation ◽  
Before And After ◽  
Factor Alpha ◽  
Metabolic Variables ◽  
Time Invariant

It is usual to study the sensitivity of metabolic variables to small (infinitesimal) changes in the magnitudes of individual parameters such as an enzyme concentration. Here, the effect that a simultaneous change in all the enzyme concentrations by the same factor alpha (Co-ordinate-Control Operation, CCO) has on the variables of time-dependent metabolic systems is investigated. This factor alpha can have any arbitrary large value. First, we assume, for each enzyme measured in isolation, the validity of the steady-state approximation and the proportionality between reaction rate and enzyme concentration. Under these assumptions, any time-invariant variable may behave like a metabolite concentration, i.e. S alpha = Sr (S-type), or like a flux, i.e. J alpha = alpha Jr (J-type). The subscripts r and alpha correspond to the values of the variable before and after the CCO respectively. Similarly, time-dependent variables may behave according to S alpha (t/alpha) = Sr (t) (S-type) or to J alpha (t/alpha) = alpha J r (t) (J-type). A method is given to test these relationships in experimental systems, and to quantify deviations from the predicted behaviour. A positive test for deviations proves the violation of some of the assumptions made. However, the breakdown of the assumptions in an enzyme-catalysed reaction, studied in isolation, may or may not affect significantly the behaviour of the system when the component reaction is embedded in the metabolic network.

Durability of Lubricated Icephobic Coatings under Multiple Icing/Deicing Cycles

2021 ◽  
Author(s):  
Valentina Donadei ◽  
Heli Koivuluoto ◽  
Essi Sarlin ◽  
Petri Vuoristo
Keyword(s):  
Industrial Applications ◽  
Power Lines ◽  
Operational Performance ◽  
Flame Spraying ◽  
Mechanical Interlocking ◽  
Properties Of Coatings ◽  
Before And After ◽  
Outdoor Environments ◽  
One Step ◽  
Ice Adhesion

Abstract In subzero conditions, atmospheric ice naturally accretes on surfaces in outdoor environments. This accretion can compromise the operational performance of several industrial applications, such as wind turbines, power lines, aviation, and maritime transport. To effectively prevent icing problems, the development of durable icephobic coating solutions is strongly needed. Here, the durability of lubricated icephobic coatings was studied under repeated icing/deicing cycles. Lubricated coatings were produced in one-step by flame spraying with hybrid feedstock injection. The coating icephobicity was investigated by accreting ice from supercooled microdroplets using an icing wind tunnel. The ice adhesion strength was evaluated by a centrifugal ice adhesion tester. The icing performance was investigated over four icing/deicing cycles. Surface properties of coatings, such as morphology, topography, chemical composition and wettability, were analyzed before and after the cycles. The results showed an increase in ice adhesion over the cycles, while a stable icephobic behaviour was retained for one selected coating. Moreover, consecutive ice detachment caused a surface roughness increase. This promotes the formation of mechanical interlocking with ice, thus justifying the increased ice adhesion. Finally, the coating hydrophobicity mainly decreased as a consequence of the damaged surface topography. In summary, lubricated coatings retained a good icephobic level after the cycles, thus demonstrating their potential for icephobic applications.

Electrochemical determination of antioxidant properties of a series of tetraphenylporphyrin derivatives and their zinc complexes

2015 ◽  
Vol 19 (09) ◽  
pp. 1032-1038 ◽  
Author(s):  
Mariya V. Tesakova ◽  
Aleksandr S. Semeikin ◽  
Vladimir I. Parfenyuk
Keyword(s):  
Antioxidant Capacity ◽  
Antioxidant Properties ◽  
Electrochemical Determination ◽  
Zinc Complexes ◽  
Oh Groups ◽  
Electron Absorption Spectra ◽  
Before And After ◽  
Phenyl Rings ◽  
Effect Of Structure

Zinc complexes of a series of substituted tetraphenylporphyrins containing OH-groups in the phenyl rings were synthesized. Their antioxidant capacity was estimated in reaction of the porphyrins with 2,2′-diphenyl-1-picrylhydrazyl (DPPH) by cyclic voltammetry. The electron absorption spectra of the all synthesized compounds before and after the reaction with 2,2′-diphenyl-1-picrylhydrazyl were recorded. The effect of structure of the porphyrins and zinc complexes on their antioxidant capacity was discussed.

scholarly journals Degradable Polymer Stars Based on Tannic Acid Cores by ATRP

Polymers ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 752 ◽  
Author(s):  
Julia Cuthbert ◽  
Saigopalakrishna S. Yerneni ◽  
Mingkang Sun ◽  
Travis Fu ◽  
Krzysztof Matyjaszewski
Keyword(s):  
Tannic Acid ◽  
Molar Mass ◽  
Gel Permeation Chromatography ◽  
Degradable Polymers ◽  
Degradable Polymer ◽  
Cytotoxicity Assays ◽  
Before And After ◽  
Phenolic Esters ◽  
Ft Ir ◽  
Waste Accumulation

Degradable polymers are crucial in order to reduce plastic environmental pollution and waste accumulation. In this paper, a natural product, tannic acid was modified to be used as a polymer star core. The tannic acid was modified with atom transfer radical polymerization (ATRP) initiators and characterized by 1H NMR, FT-IR, and XPS. Twenty-five arm polymer stars were prepared by photoinduced ATRP of poly(methyl methacrylate) (PMMA) or poly(oligo(ethylene oxide) methacrylate) (molar mass Mw = 300 g/mol) (P(OEO300MA)). The polymer stars were degraded by cleaving the polymer star arms attached to the core by phenolic esters under mild basic conditions. The stars were analyzed before and after degradation by gel permeation chromatography (GPC). Cytotoxicity assays were performed on the P(OEO300MA) stars and corresponding degraded polymers, and were found to be nontoxic at the concentrations tested.

Study of Damage Mechanisms in Cold-Sprayed 316L-Matrix Composite Coatings Using Novel Impact-Sliding Testing

2014 ◽  
Vol 922 ◽  
pp. 452-462 ◽  
Author(s):  
R. Maestracci ◽  
N. Fabrègue ◽  
M. Jeandin ◽  
G. Bouvard ◽  
M. Messaadi ◽  
...  
Keyword(s):  
Cold Spray ◽  
High Performance ◽  
Composite Coatings ◽  
Industrial Applications ◽  
Damage Mechanisms ◽  
Coating Composition ◽  
Before And After ◽  
Coating Microstructure ◽  
Service Conditions ◽  
Sliding Test

Cold spray is now well recognized as one of the most powerful and efficient coating process because it is cost-attractive and “green”. However, this process still shows limitations to achieve coatings for highly-demanding service conditions such as those required in certain automotive and/or aircraft applications. Beyond these limitations, cold spray is expected to compete with conventional P/M routes.The present work therefore focussed on the study of damage mechanisms in cold-sprayed AISI 316L and 316L-matrix–Cu composites coatings due to high-loading conditions. Different damage mechanisms could occur depending on the content of Cu particle addition, due to changes in the response of the microstructure to the loading. These mechanisms were studied using the newly-developed “impact-sliding” test. In this test, a steel ball impacts the coating surface at a given frequency, with a fixed angle. The influence of major testing parameters was investigated.Microstructures before and after testing were studied using optical microscopy, scanning electron microscopy (SEM), and microprobe analysis in addition to 3D optical profilometry of impacted areas. Damage mechanisms were seen to be of two types, i.e. plastic deformation and wear. These resulted in decohesion of splats, formation of wear debris and formation of a layer with a tribologically-transformed structure (TTS) at the contact surface.Results showed that cold spray could be claimed to be suitable for the achievement of high-performance coatings for industrial applications provided that the coating microstructure can be controlled. This could be done using a composite approach to the coating composition.

Adsorption of monodisperse polybutadienes on carbon black, 3 Displacement of pre-adsorbed molecules by the same polymer. Conformational and molecular weight effects

e-Polymers ◽  
2005 ◽  
Vol 5 (1) ◽  
Author(s):  
Kathy Vuillaume ◽  
Bassel Haidar ◽  
Alain Vidal
Keyword(s):  
Molecular Weight ◽  
Driving Force ◽  
Polymer Concentration ◽  
Gel Permeation Chromatography ◽  
Polymer Chains ◽  
Gel Permeation ◽  
Conformational Factor ◽  
Before And After ◽  
Displacement Processes

AbstractDisplacement of pre-adsorbed macromolecules by the same polymer, polybutadiene, of the same or of different molecular weight was studied in solution and in the bulk. The effect of polymer concentration on pre-adsorption and displacement processes was determined. Displacement was investigated by gel permeation chromatography and by determination of the amount of bound polymer before and after displacement. A conformational factor was established as a major driving force - besides molecular weight - in the displacement process. Polymer chains adsorbed in flat conformation had the highest adsorption stability and could not be displaced by any other molecular weight of the same polymer.

Characterization, Modification and Rheology of Green Clay

2015 ◽  
Vol 820 ◽  
pp. 60-64
Author(s):  
Leila Verônica da Rocha-Gomes ◽  
Antônio José Santana ◽  
Camila Martini Matos ◽  
Valquíria de Fátima Justo ◽  
Maria Das Graças Silva-Valenzuela ◽  
...  
Keyword(s):  
Water Absorption ◽  
Rheological Properties ◽  
Apparent Density ◽  
Industrial Applications ◽  
Clay Sample ◽  
Oil Drilling ◽  
Smectite Clays ◽  
Swelling Capacity ◽  
Before And After ◽  
Green Clay

Smectite clays or bentonites are used in several industrial applications. The aim of this study was to describe the characterization and organophilization of a green clay sample coming from the State of Paraíba, Brazil. The clay was characterized by XRD, XRF, CEC, SEM, stereoscopic microscopy, Fann viscosity (before and after the organophilization process), swelling capacity in water and some organic solvents. Prismatic specimens were conformed by pressing, for which were conformed the mechanical sthegth after drying at 110°C and after burning at 950°C. The burned specimens were analyzed to evaluate dimensional variations, water absorption, apparent porosity and apparent density. XRD showed that the sample was constituted mainly for montmorillonite claymineral. Analysis of rheological properties of the modified clay indicates its potential to meet the specifications of the standard N-2604 of Petrobras, concerning clays used to oil drilling.

scholarly journals Novel Epoxy Activated Hydrogels for Solving Lactose Intolerance

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Magdy M. M. Elnashar ◽  
Mohamed E. Hassan
Keyword(s):  
Lactose Intolerance ◽  
Epoxy Group ◽  
Immobilized Enzymes ◽  
Aldehyde Group ◽  
Medical Problem ◽  
Enzyme Concentration ◽  
Lactose Hydrolysis ◽  
World Population ◽  
Oh Groups ◽  
Michaelis Constants

“Lactose intolerance” is a medical problem for almost 70% of the world population. Milk and dairy products contain 5–10% w/v lactose. Hydrolysis of lactose by immobilized lactase is an industrial solution. In this work, we succeeded to increase the lactase loading capacity to more than 3-fold to 36.3 U/g gel using epoxy activated hydrogels compared to 11 U/g gel using aldehyde activated carrageenan. The hydrogel’s mode of interaction was proven by FTIR, DSC, and TGA. The high activity of the epoxy group was regarded to its ability to attach to the enzyme’s –SH, –NH, and –OH groups, whereas the aldehyde group could only bind to the enzyme’s –NH2group. The optimum conditions for immobilization such as epoxy chain length and enzyme concentration have been studied. Furthermore, the optimum enzyme conditions were also deliberated and showed better stability for the immobilized enzyme and the Michaelis constants,KmandVmax, were doubled. Results revealed also that both free and immobilized enzymes reached their maximum rate of lactose conversion after 2 h, albeit, the aldehyde activated hydrogel could only reach 63% of the free enzyme. In brief, the epoxy activated hydrogels are more efficient in immobilizing more enzymes than the aldehyde activated hydrogel.

scholarly journals End-Group Evaluation of HEMA Initiated Poly(ε-caprolactone) Macromonomers via Enzymatic Ring-Opening Polymerization

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
N. Ugur Kaya ◽  
Y. Avcibasi Guvenilir
Keyword(s):  
Molecular Weight ◽  
Ring Opening ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Ring Opening Polymerization ◽  
Enzyme Concentration ◽  
Polymer Chains ◽  
Side Reactions ◽  
Initiator Concentration ◽  
Lower Temperature

Poly(ε-caprolactone) (PCL) macromonomers comprising acrylate end-functionality were synthesized via enzymatic ring-opening polymerization (eROP) by utilizing commercially availableCandida antarcticaLipase B (CALB), Novozyme-435. 2-Hydroxyethyl methacrylate (HEMA) was purposed to be the nucleophilic initiator in eROP. The side reactions generated due to the cleavage of ester bonds in HEMA and the growing polymer chains were investigated through altering polymerization period, initiator concentration, temperature, and enzyme concentration.1H NMR evaluations showed that minimum quantities of side reactions were in lower temperatures, initiator concentration, enzyme concentration, and lower monomer conversions. Gel permeation chromatography (GPC) results revealed that lower polydispersity along with number-average molecular weight of end-functionalized PCL macromonomers was obtained depending on higher initiator/monomer ratios, lower temperature (60°C), enzyme concentration (100 mg), and/or polymerization time (2 h). Furthermore, 0.1 HEMA/ε-caprolactone (CL) ratio had higher molecular weight than 0.5 HEMA/CL ratio, while keeping a close value of methacrylate transfer, total methacrylate end-groups, and lower polyester transfer.

Springback Evaluation of Parts Made by Single-Point Incremental Sheet Forming

2011 ◽  
Author(s):  
Paolo Bosetti ◽  
Stefania Bruschi
Keyword(s):  
Process Parameters ◽  
Incremental Forming ◽  
Elastic Recovery ◽  
Single Point ◽  
Industrial Applications ◽  
Geometrical Parameters ◽  
Forming Process ◽  
Part Geometry ◽  
Before And After ◽  
Measuring Machine

One of the major drawbacks of single-point incremental forming process for sheet metal (SPIF) consists in the poor geometrical accuracy of formed parts. This limits the use of SPIF technology and has pushed the development of alternative incremental processes—such as the two-points incremental forming—aimed at improving the forming accuracy. However, these processes require the use of supporting dies and they therefore reduce the competitive advantage of SPIF process. The possibility to compensate for part springback, in order to have the part geometry as close as possible to the nominal one, represents one of the major challenges to make SPIF process suitable for real industrial applications. However, any possible approach in springback compensation must pass through the comprehension of the springback phenomenon. The objective of the paper is to analyze the springback of parts made by SPIF, by evaluating the influence that elastic recovery before and after the part unclamping has on the final part geometry. A SPIF experimental campaign was carried out on a truncated pyramid as case study, by varying both the part geometrical parameters (the wall angle and the height), and the process parameters (the tool step-down size and the feed rate). The material used in this study was the duplex steel DP600 provided in 0.8 mm thick sheets. After forming—but before unclamping—the part geometry was measured by means of of an electronic touch probe mounted on the machine tool-holder, in order to investigate the elastic recovery due to the successive tool laps. After unclamping, the part geometry was measured on a coordinate measuring machine. The influence of geometrical and process parameters was analyzed and the contribution of elastic recovery before and after the part unclamping was assessed.

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