On Laccase-Catalyzed Polymerization of Biorefinery
Lignin Fractions and Alignment of Lignin Nanoparticles on the Nanocellulose
Surface via One-Pot Water-Phase Synthesis
posted on 2021-06-21, 11:36authored byLuyao Wang, Liping Tan, Liqiu Hu, Xiaoju Wang, Rajesh Koppolu, Teija Tirri, Bas van Bochove, Petri Ihalainen, Liji Sobhana Seleenmary Sobhanadhas, Jukka V. Seppälä, Stefan Willför, Martti Toivakka, Chunlin Xu
Two series of well-defined
lignin fractions derived from birch
and spruce alkaline lignin (AL) by sequential solvent fractionation
(i-PrOH-EtOH-MeOH) were engaged in a structure–property-application
relationship study. The bacterial-derived alkaliphilic laccase (MetZyme)
extensively catalyzed the oxidation and polymerization of AL fractions
in an aqueous alkaline solution (pH 10). Lignin fractions with low
molar mass reached a higher polymerization degree due to more phenolic-OH
groups serving as reactive sites of oxidation and better lignin-laccase
accessibility arose from a lower lignin condensation degree than the
high molar mass ones. In comparison, AL fractions from spruce were
found to be less reactive toward the laccase-catalyzed polymerization
than those from birch, which was attributed to the much pronounced
aryl-vinyl moieties’ oxidation. Furthermore, in situ polymerization of birch AL fractions using microfibrillated cellulose
as a structural template was conducted in an aqueous medium and a
dispersion of nanocellulose with its fiber network evenly coated by
aligned lignin nanoparticles was obtained. The present study not only
provides fundamental insights on the laccase-assisted oxidation and
polymerization of lignin but also presents a new perspective for valorizing
lignin in biobased fiber products through green processing of solvent
fractionation and enzymatic treatment.