Enzymatic treatment improves fast pyrolysis product selectivity of softwood and hardwood lignin

Abstract

Fast pyrolysis of lignin is still struggling in efficiency and scalable utilization. The low product selectivity thereby represents one of the most challenging issues. White-rot fungi have been widely used in bio-pretreatment of lignocellulosic biomass, where ligninolytic enzymes have been evidenced to modify lignin structures and enhance bio-refining efficiency. We thus treated lignin from both softwood (ginkgo) and hardwood (poplar) with enzymatic cocktail from white-rot fungus for fast pyrolysis. Both ginkgo and poplar lignin had much improved product selectivity at lower temperature after enzymatic modification, in particular, the 2-methoxy-phenol production from ginkgo lignin. Besides the improved product selectivity, the residue bio-char from pyrolysis had much improved surface area with more porous structures. Mechanistic study showed that the improvement of lignin pyrolysis products might attribute to demethoxylation and interunit linkage cleavage of lignin during enzymatic treatment. All these results highlighted that the product selectivity and bio-char performances have been synergistically improved by enzymatic treatment, which could thus pave a new way for enhancing fast pyrolysis efficiency. Overall, using softwood and hardwood lignin, this research has presented a new strategy using ligninolytic enzyme to modify lignin for synergistically improving product selectivity and bio-char performances, which opened up a new avenue for lignin valorization.

Keywords: Enzymatic treatment; Fast pyrolysis; Lignin valorization; Phenolic monomers; White-rot fungus.