Enzymatically and chemically oxidized lignin nanoparticles for biomaterial applications

Area of Science:

• Biomaterials Science
• Nanotechnology
• Polymer Chemistry

Background:

• Kraft lignin is an abundant lignocellulosic byproduct with potential for valorization.
• Developing stable, functional lignin-based nanoparticles is crucial for advanced applications.
• Existing methods for lignin modification often involve harsh chemicals or result in unstable particles.

Purpose of the Study:

• To prepare cross-linked and decolorized lignin nanoparticles (LNPs) from softwood Kraft lignin.
• To evaluate the stability and redispersibility of these LNPs in various solvents.
• To explore enzymatic and chemical methods for LNP modification and decolorization.

Main Methods:

• Enzymatic cross-linking using laccases (Trametes hirsuta and Melanocarpus albomyces).
• Chemical decolorization using ultrasonication and H2O2 under alkaline conditions.
• Characterization using HPSEC, oxygen consumption, zeta potential, DLS, AFM, and TEM.

Main Results:

• Stable, spherical colloidal lignin particles (CLPs, ~200 nm) were prepared and could be dried and redispersed in water or THF.
• Laccase treatment confirmed reactivity and led to intraparticular cross-linking, evidenced by surface carboxylic acid groups and minor size distribution changes.
• Decolorization was achieved without degradation, yielding stable LNPs suitable for further applications.

Conclusions:

• Enzymatic and chemical modifications enable the creation of stable, decolorized lignin nanoparticles from Kraft lignin.
• These lignin nanoparticles exhibit excellent redispersibility and stability, making them promising for bionanomaterial applications.
• The developed methods offer a sustainable route for valorizing Kraft lignin into high-value nanomaterials for medicine, food, and cosmetics.