This presentation reports a study that explored a unique lignin-unlocking process in wood-feeding termites (WFT) Coptotermes formosanus (Shiraki) for subsequent effective polysaccharide utilization during the digestion of woody biomass. Utilization of plant cell wall (PCW) for production of biofuels and biochemical offers great potential for alleviation of the pressure created by the increase in energy consumption and the finite supply of fossil fuels. Pretreating PCW to unlock the protection of cellulose from lignin as an essential step for its enzymatic hydrolysis to fermentable sugars is currently the major barrier for economical production of lignocellulosic-biomass-based fuels. The capability of cellulose utilization by WFT worker (up to 95% cellulose within 24 hrs) makes it a promising model system for discovering and mimicking the novel pretreatment mechanisms. A series of advanced analytical techniques were employed for characterization of termite digested softwood particles. Obtained results indicate that termites stepwise and selectively modify lignin and associated aromatic biopolymers, with minor mineralization. More specially, the effective wood assimilation in termite is initiated with lignin phenolic demethoxylation, dehydroxylation, carboxylation and lignolytic ether linkage(ߖ�', ߖ5', 5�5') dissociation. These reactions enhanced lignin hydrophilicity and physically/chemically reduced its inhibition effect on cellulases. The lignolytic catalyzing system of termite appeared leaving lignin backbone alone, thus consuming less energy and producing negligible lignin-derived inhibitors to subsequent hydrolysis and fermentation. The unique lignin-unlocking mechanism in termite, together with the varied micro-environments measured in its gut compartment provide clue for existence of non-enzymatic lignin modifying system in termite fore- and/or midgut. This was further supported by the similar mechanisms of termite system and in-vitro mimicking process. Overall, this study provides new information for lignin-unlocking mechanisms during PCW deconstruction process by termite. This further provides insights towards development of new pretreatment processes for biochemical conversion of lignocellulose fuels and value-added chemicals.

Selective lignin modification process in termites for effective lignocellulose deconstruction

245th National Meeting (2013)

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