Given the current state of environmental affairs and that our future on this planet as we know it is in jeopardy, research and development into greener and more sustainable technologies within the chemical and forest products industries is at its peak. Given the global scale of these industries, the need for environmentally benign practices is propelling new green processes. These challenges are also impacting academic research and our reagents of interest are laccases. These enzymes are employed in a variety of biotechnological applications due to their native function as catalytic oxidants. They are about as green as it gets when it comes to chemical processes, requiring O as their only co-substrate and producing H O as the sole by-product. The following account will review our twenty year journey on the use of these enzymes within our research group, from their initial use in biobleaching of kraft pulps and for fiber modification within the pulp and paper industry, to their current application as green catalytic oxidants in the field of synthetic organic chemistry.

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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.

Please cite this article as: M.D. Cannatelli, A.J. Ragauskas, Laccase-catalyzed synthesis of 2,3-ethylenedithio-1,4-quinones, Journal of Molecular Catalysis B: Enzymatic (2015), http://dx.A c c e p t e d M a n u s c r i p t Highlights: Laccase-catalyzed synthesis of 2,3-ethylenedithio-1,4-quinonesx Laccase-catalyzed cross-coupling of 1,2-ethanedithiol with substituted hydroquinones.x Green, one-pot, enzymatic synthesis of 2,3-ethylenedithio-1,4-quinones.x Stability of in situ generated 1,4-quinone vital factor in product formation.x Eco-friendly laccases catalyze the reduction of O 2 to H 2 O.

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Lignin, one of the major chemical constituents of woody biomass, is the second most abundant biopolymer found in nature. The pulp and paper industry has long produced lignin on the scale of millions of tons annually as a by-product of the pulping process, and the dawn of cellulosic ethanol production has further contributed to this amount. Historically, lignin has been perceived as a waste material and burned as a fuel for the pulping process. However, recent research has been geared toward developing cost-effective technologies to convert lignin into valuable commodities. Attributing to the polyphenolic structure of lignin, enzymatic modification of its surface using laccases (benzenediol:oxygen oxidoreductases, EC 1.10.3.2) has demonstrated to be highly successful. The current study aims at developing lignin-core hyperbranched copolymers via the laccase-assisted copolymerization of kraft lignin with methylhydroquinone and a trithiol. Based on the physical properties of the resulting material, it is likely that crosslinking reactions have taken place during the drying process to produce a copolymeric network rather than discrete hyperbranched copolymers, with NMR data providing evidence of covalent bonding between monomers. Preliminary thermal analysis data reveals that the copolymeric material possesses a moderate glass transition temperature and exhibits good thermostability, thus may have potential application as a lignin-based thermoplastic. Scanning electron microscopy images confirm the smooth, glossy surface of the material and that it is densely packed. The presented results are a sustainable, ecofriendly, economic method to create an exciting novel biomaterial from a renewable feedstock while further enhancing lignin valorization.

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