Conversion of lignin into value-added materials and chemicals via laccase-assisted copolymerization

Abstract

With today's environmental concerns and the diminishing supply of the world's petroleum-based chemicals and materials, much focus has been directed toward alternative sources. Woody biomass presents a promising option due to its sheer abundance, renewability, and biodegradability. Lignin, a highly irregular polyphenolic compound, is one of the major chemical constituents of woody biomass and is the second most abundant biopolymer on Earth, surpassed only by cellulose. The pulp and paper and cellulosic ethanol industries produce lignin on the scale of millions of tons each year as a by-product. Traditionally, lignin has been viewed as a waste material and burned as an inefficient fuel. However, in recent decades, research has focused on more economical ways to convert lignin into value-added commodities, such as biofuels, biomaterials, and biochemicals, thus developing and strengthening the concept of fully integrated biorefineries. Owing to the phenolic structure of lignin, it is possible to enzymatically graft molecules onto its surface using laccases (benzenediol:oxygen oxidoreductases, EC 1.10.3.2) to create exciting novel biomaterials. These environmentally friendly enzymes use oxygen as their only co-substrate and produce water as their sole by-product, and have thus found great industrial application. This mini-review highlights recent advances in the field of laccase-facilitated functionalization of lignin as well as promising future directions for lignin-based polymers.

Expression of a new laccase from Moniliophthora roreri at high levels in Pichia pastoris and its potential application in micropollutant degradation

“…Laccases have gained significant attention due to emerging applications including biomass degradation, biofuel cells, biocatalysis and bioremediation (Cannatelli and Ragauskas 2016; Kudanga et al 2011; Mikolasch and Schauer 2009; Senthivelan et al 2016; Strong and Claus 2011; Suzuki et al 2003). However, low expression levels have been recognized as a major obstacle to industrial use of these enzymes (Piscitelli et al 2010).…”

Effect of Laccase-Mediated Biopolymer Grafting on Kraft Pulp Fibers for Enhancing Paper’s Mechanical Properties

“…This can be explained since the mediator acts after being oxidized (med ox) by the enzyme and further oxidizes any substrate with a lower chemical potential. Med ox could initiate a radical coupling polymerization or a nucleophilic addition [39]. This could explain why GA is better in performance than VA and 1,2–DHB.…”

Chemo-enzymatically prepared lignin nanoparticles for value-added applications

“…Laccase-catalyzed cross-linking reactions on lignin and lignin model compounds in different solvent systems have been extensively studied to understand the structure–function properties of the enzymes (Cannatelli and Ragauskas 2016; Van de Pas et al 2011). Recently Mattinen et al (2018a) showed that fungal laccases such as Trametes hirsuta (ThL) and Melanocarpus albomyces (MaL) could be used to cross-link CLPs, increasing their stability in organic solvents.…”

“…Despite several attractive properties such as biodegradability, UV-absorptivity, excellent thermal stability, antioxidant and antimicrobial properties, reactivity via radicalization, intense color varying from yellow via red to black, lignin is largely considered as waste from biorefinery, pulp and paper processes (Patil and Argyropoulos 2017; Qian et al 2014). Since it is mostly burnt for energy or used as animal feed (Beisl et al 2017; Yang et al 2016a; Gilca et al 2015), the need for the development of green chemo-enzymatic lignin valorization technologies is apparent (Ragauskas et al 2014; Cannatelli and Ragauskas 2016; Husarcíková et al 2018; Ma et al 2018). The use of technical lignin in nanoparticulate morphology (Duval and Lawoko 2014; Henn and Mattinen 2019) is an interesting method which could potentially overcome many challenges in the processing regarding the polymer’s heterogeneity and poor water solubility.…”