Special Issue "Properties, Applications and Perspectives of Lignin"

A special issue of Polymers (ISSN 2073-4360).

Deadline for manuscript submissions: 15 November 2019

Special Issue Editors

Guest Editor
Dr. Enrico Sanjust

Dipartimento di Scienze Biomediche, Università di Cagliari, Cagliari, Italy
Website | E-Mail
Phone: +390706754518
Interests: biomimetic catalysis; applied enzymology; fungal phenol oxidases
Guest Editor
Dr. Paolo Zucca

Dipartimento di Scienze Biomediche, Università di Cagliari, Cagliari, Italy
E-Mail
Interests: catalytic degradation of organic pollutants; biochemical characterization of plant extracts

Special Issue Information

Dear Colleagues,

Lignin is among the most abundant organic substances, and is produced by vascular plants. It is an irregular aliphatic–aromatic heteropolymer based on C6C3 monomeric units. Arising from radical chain reactions, its hydrolysis to afford such monomeric units is quite a difficult task, whereas its highly cross-linked nature makes it almost insoluble in the common solvents, unless it is more or less deeply altered in its native structure.

Therefore, lignin biosynthesis deserves attention in order to elucidate the exact mechanism(s) by which plants build this robust structural polymer, and to intervene by means of genetic engineering tools to modulate its physico-chemical and mechanical properties. This could open the way towards tailor-made lignins (and consequently, woods) whose features could be pre-determined to optimize the required performances once the timber has to be utilized.

For the pulp and paper industry, lignin should be removed to leave cellulose fibers. However, the various processes that are currently available are still awaiting a full optimization, in terms of both efficiency and environmental impact: huge amounts of aggressive reagents are required, together with harsh and energy-consuming treatments, and produce enormous quantities of high-impact wastes.

Biological (mainly enzymatic) and biomimetic treatments are promising but far from showing a reasonable efficiency, so they require further deep studies to substantially move ahead.

This Special Issue welcomes experimental studies and reviews describing new insights and/or encompassing the state-of-the-art in the fields of lignin biosynthesis and its regulation/modulation, improvements of delignification treatments (both chemical and biological/biomimetic), and new frontiers in lignin utilization—possibly after suitable modification—as a biomaterial and/or as a promising source of derived chemicals.

Dr. Enrico Sanjust
Dr. Paolo Zucca
Guest Editors

Manuscript Submission Information

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Keywords

  • lignin biosynthesis
  • chemicals from lignin
  • heteropolymer
  • lignin-based materials

Published Papers (3 papers)

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Research

Open AccessArticle
Efficient Conversion of Lignin Waste to High Value Bio-Graphene Oxide Nanomaterials
Polymers 2019, 11(4), 623; https://doi.org/10.3390/polym11040623
Received: 4 March 2019 / Revised: 25 March 2019 / Accepted: 2 April 2019 / Published: 4 April 2019
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Abstract
Lignin graphene oxide was oxidized after Kraft lignin was graphitized by thermal catalytic conversion. The reduced lignin graphene oxide was derived from lignin graphene oxide through thermal reduction treatment. These Kraft lignin, lignin graphite, lignin graphene oxide, and reduced lignin graphene oxide were [...] Read more.
Lignin graphene oxide was oxidized after Kraft lignin was graphitized by thermal catalytic conversion. The reduced lignin graphene oxide was derived from lignin graphene oxide through thermal reduction treatment. These Kraft lignin, lignin graphite, lignin graphene oxide, and reduced lignin graphene oxide were characterized by scanning electron microscopy, raman microscopy, high-resolution transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, atomic force microscopy and thermogravimetric analysis. The results showed lignin graphite converted from Kraft lignin had fewer layers with smaller lateral size than natural graphite. Moreover, lignin graphene oxide was successfully produced from lignin graphite by an oxidation reaction with an hour-long reaction time, which has remarkably shorter reaction time than that of graphene oxide made from natural graphite. Meanwhile, this lignin-derived graphene oxide had the same XRD, FTIR and Raman peaks as graphene oxide oxidized from natural graphite. The SEM, TEM, and AFM images showed that this lignin graphene oxide with 1–3 average layers has a smaller lateral size than that of graphene oxide made from natural graphite. Moreover, the lignin graphene oxide can be reduced to reduced lignin graphene oxide to fabricate graphene-based aerogel, wire, and film for some potential applications. Full article
(This article belongs to the Special Issue Properties, Applications and Perspectives of Lignin)
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Open AccessArticle
Oxidative Depolymerization of Cellulolytic Enzyme Lignin over Silicotungvanadium Polyoxometalates
Polymers 2019, 11(3), 564; https://doi.org/10.3390/polym11030564
Received: 25 January 2019 / Revised: 4 March 2019 / Accepted: 20 March 2019 / Published: 26 March 2019
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Abstract
The aim of this study was to explore the catalytic performance of the oxidative depolymerization of enzymatic hydrolysis lignin from cellulosic ethanol fermentation residue by different vanadium substituted Keggin-type polyoxometalates (K5[SiVW11O40], K6[SiV2W10 [...] Read more.
The aim of this study was to explore the catalytic performance of the oxidative depolymerization of enzymatic hydrolysis lignin from cellulosic ethanol fermentation residue by different vanadium substituted Keggin-type polyoxometalates (K5[SiVW11O40], K6[SiV2W10O40], and K6H[SiV3W9O40]). Depolymerized products were analyzed by gel permeation chromatography (GPC), gas chromatography–mass spectrometer (GC/MS), and two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance (2D HSQC NMR) analysis. All catalysts showed an effective catalytic activity. The best result, concerning the lignin conversion and lignin oil production, was obtained by K6[SiV2W10O40], and the highest yield of oxidative depolymerization products of 53 wt % was achieved and the main products were monomer aromatic compounds. The HSQC demonstrated that the catalysts were very effective in breaking the β-O-4 structure, the dominant linkage in lignin, and the GPC analysis demonstrated that the molecular of lignin was declined significantly. These results demonstrate the vanadium substituted silicotungstic polyoxometalates were of highly active and stable catalysts for lignin conversion, and this strategy has the potential to be applicable for production of value-added chemicals from biorefinery lignin. Full article
(This article belongs to the Special Issue Properties, Applications and Perspectives of Lignin)
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Graphical abstract

Open AccessArticle
The Impact of Lignin Structural Diversity on Performance of Cellulose Nanofiber (CNF)-Starch Composite Films
Polymers 2019, 11(3), 538; https://doi.org/10.3390/polym11030538
Received: 23 February 2019 / Revised: 15 March 2019 / Accepted: 18 March 2019 / Published: 21 March 2019
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Abstract
Lignin fractions having different molecular weights and varied chemical structures isolated from kraft lignins of both softwood and hardwood via a sequential solvent fractionation technique were incorporated into a tunicate cellulose nanofibers (CNF)—starch mixture to prepare 100% bio-based composite films. The aim was [...] Read more.
Lignin fractions having different molecular weights and varied chemical structures isolated from kraft lignins of both softwood and hardwood via a sequential solvent fractionation technique were incorporated into a tunicate cellulose nanofibers (CNF)—starch mixture to prepare 100% bio-based composite films. The aim was to investigate the impact of lignin structural diversity on film performance. It was confirmed that lignin’s distribution in the films was dependent on the polarity of solvents used for fractionation (acetone > methanol > ethanol > ethyl acetate) and influenced the optical properties of the films. The –OH group content and molecular weight of lignin were positively related to film density. In general, the addition of lignin fractions led to decrease in thermal stability and increase in Young’s modulus of the composite films. The modulus of the films was found to decrease as the molecular weight of lignin increased, and a higher amount of carboxyl and phenolic –OH groups in the lignin fraction resulted in films with higher stiffness. The thermal analysis showed higher char content formation for lignin-containing films in a nitrogen atmosphere with increased molecular weight. In an oxygen atmosphere, the phenol content, saturated side chains and short chain structures of lignin had impacts on the maximum decomposition temperature of the films, confirming the relationship between the chemical structure of lignin and thermo-oxidative stability of the corresponding film. This study addresses the importance of lignin diversities on composite film performance, which could be helpful for tailoring lignin’s applications in bio-based materials based on their specific characteristics. Full article
(This article belongs to the Special Issue Properties, Applications and Perspectives of Lignin)
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Graphical abstract

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