Enzymatically and chemically oxidized lignin nanoparticles for biomaterial applications

Abstract

Cross-linked and decolorized lignin nanoparticles (LNPs) were prepared enzymatically and chemically from softwood Kraft lignin. Colloidal lignin particles (CLPs, ca. 200 nm) in a non-malodorous aqueous dispersion could be dried and redispersed in tetrahydrofuran (THF) or in water retaining their stability i.e. spherical shape and size. Two fungal laccases, Trametes hirsuta (ThL) and Melanocarpus albomyces (MaL) were used in the cross-linking reactions. Reactivity of ThL and MaL on Lignoboost™ lignin and LNPs was confirmed by high performance size exclusion chromatography (HPSEC) and oxygen consumption measurements with simultaneous detection of red-brown color due to the formation of quinones. Zeta potential measurements verified oxidation of LNPs via formation of surface-oriented carboxylic acid groups. Dynamic light scattering (DLS) revealed minor changes in the particle size distributions of LNPs after laccase catalyzed radicalization, indicating preferably covalent intraparticular cross-linking over polymerization. Changes in the surface morphology of laccase treated LNPs were imaged by atomic force (AFM) and transmission emission (TEM) microscopy. Furthermore, decolorization of LNPs without degradation was obtained using ultrasonication with HO in alkaline reaction conditions. The research results have high impact for the utilization of Kraft lignin as nanosized colloidal particles in advanced bionanomaterial applications in medicine, foods and cosmetics including different sectors from chemical industry.

Spherical lignin particles: a review on their sustainability and applications

“…168 (c) Oxidation of lignin particles induced by enzymes. 169 (d) Effect of pH on the stability, as far as hydrodynamic diameter, of irregular and spherical-shaped lignin nanoparticles. 49 (e) Effect of thermal treatments on the lignin particles dispersions properties.…”

Applications of Microbial Laccases: Patent Review of the Past Decade (2009–2019)

“…The potential laboratory applications of laccases also extend to the field of nanotechnology in regard to the synthesis and/or modification of nanomaterials for various sectors. The development of enzymatically oxidized lignin nanosized colloidal particles for various applications was recently reported [178], as well as the synthesis of hybrid nanoflowers containing laccase as a nanobiocatalyst for the degradation of dyes (CN104789549A, CN105536691A) [179]. For example, the technical problems that were encountered in the application of laccases for xenobiotics removal, such as their low biodegradability and removal rate, was solved by adsorption of laccase to carbon nanotubes, resulting in enhanced enzyme activity, as well as thermophilic and psychrophilic stability (CN109912048A).…”

Colloidal Lignin Particles as Adhesives for Soft Materials

“…For the analyses, enzymatically polymerized and cross-linked lignin's including molecular weight standards (194 Da to 0.1 kDa) were dissolved in NaOH (0.1 M) in two concentrations (0.1 and 0.5 mg ml -1 ). Weight-average molar mass (MW) of the samples were analysed by Agilent 1260 Infinity equipped with a UV detector (USA) as previously [39,52].…”

“…CLPs are stable in wide pH range [25]. However, due to better electrostatic stability in alkaline conditions the reactivity of CLPs is much higher than in acidic conditions [63,39]. For medical, cosmetic and food applications, it is pivotal that tailored CLPs are stable in physiological conditions.…”

“…Adhesives based on nanobridging via hard inorganic NPs [16] as well as colloidal mesoporous silica (CMS) particles [68] have been proposed as alternatives for traditional medical adhesives. Since the adhesion energy is proportional to the surface area of NPs, enzymatically cross-linked CLPs [39] with tailored functionalities could be potential additives for medical adhesives following enzymatic or thermal treatment for fast curing shown above.…”