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. 2020 Oct 24;25(21):4921.
doi: 10.3390/molecules25214921.

Biocatalytic Strategy for Grafting Natural Lignin with Aniline

Sabina Gabriela Ion  1 , Teodor Brudiu  1 , Anamaria Hanganu  2 , Florentina Munteanu  3 , Madalin Enache  4 , Gabriel-Mihai Maria  4 , Madalina Tudorache  1 , Vasile Parvulescu  1
Affiliations

Biocatalytic Strategy for Grafting Natural Lignin with Aniline

Sabina Gabriela Ion et al. Molecules. .

Abstract

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.

Keywords: amino-functionalization; biocatalysis; grafting bioprocess; lignin; peroxidase enzyme.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
Building blocks and aromatic constituents of lignin.
Scheme 1
Scheme 1
Grafting lignin with aniline using enzymatic biocatalysis.
Figure 2
Figure 2
Enzyme screening for the grafting process of lignin with aniline. Experimental conditions: 21.70 mg/mL AL, 23.30 mM aniline, 192 mM H2O2 (30%, w/w), 11% (v/v) peroxidase enzyme (2.5 U mg−1 peroxidase activity) and 22% MeOH in PBS (10 mM, pH 7.4); 24 h, 40 °C and 1000× g rpm.
Figure 3
Figure 3
The influence of the concentration of the biocatalyst on the grafting bioprocess. Experimental conditions: 21.70 mg/mL AL, 23.30 mM aniline, 192 mM H2O2 (30%, w/w), HRP enzyme and 22% MeOH in PBS (10 mM, pH 7.4); 24 h, 40 °C and 1000× g rpm.
Figure 4
Figure 4
Tests with different types of lignin in the grafting bioprocess. Experimental conditions: 21.70 mg/mL lignin, 23.30 mM aniline, 192 mM H2O2 (30%, w/w), 11% (v/v) peroxidase enzyme (2.5 U mg−1 peroxidase activity) and 22% MeOH in PBS (10 mM, pH 7.4); 24 h, 40 °C and 1000× g rpm.
Figure 5
Figure 5
Differences between original and grafted lignins related to free –OH groups.
Figure 6
Figure 6
Conductivity measurements for original and grafted lignins.
Figure 7
Figure 7
Thermogravimetric analysis (TGA) profiles of AL and AG.
Figure 8
Figure 8
Scanning electron microscopy (SEM) images of (A) AL, (B) AG, (C) KL, (D) KG.
Scheme 2
Scheme 2
Pretreatment and analysis of the reacted mixture after the grafting bioprocess.
See this image and copyright information in PMC

References

    1. Sjöström E. Wood Chemistry. 2nd ed. Academic Press; San Diego, CA, USA: 1993. pp. 71–89.
    1. Yang H., Yan R., Chen H., Zheng C., Lee D.H., Liang D.T. In-Depth Investigation of Biomass Pyrolysis Based on Three Major Components: Hemicellulose, Cellulose and Lignin. Energy Fuels. 2006;20:388–393. doi: 10.1021/ef0580117. - DOI
    1. Zakzeski J., Bruijnincx P.C.A., Jongerius A.L., Weckhuysen B.M. The Catalytic Valorization of Lignin for the Production of Renewable Chemicals. Chem. Rev. 2010;110:3552–3599. doi: 10.1021/cr900354u. - DOI - PubMed
    1. Welker C.M., Balasubramanian V.K., Petti C., Rai K.M., DeBolt S., Mendu V. Engineering Plant Biomass Lignin Content and Composition for Biofuels and Bioproducts. Energies. 2015;8:7654–7676. doi: 10.3390/en8087654. - DOI
    1. Rencoret J., Gutiérrez A., Nieto L., Jiménez-Barbero J., Faulds C.B., Kim H., Ralph J., Martínez Á.T., del Río J.C. Lignin Composition and Structure in Young versus Adult Eucalyptus globulus Plants. Plant Physiol. 2011;155:667–682. doi: 10.1104/pp.110.167254. - DOI - PMC - PubMed

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