Biodegradation of hardwood lignocellulosics by the western poplar clearwing borer, Paranthrene robiniae (Hy. Edwards).

Lignin in plant cell wall is a source of useful chemicals and also the major barrier for saccharification of lignocellulosic biomass for producing biofuel and bioproducts. Enzymatic lignin degradation/modification process could bypass the need for chemical pretreatment and thereby facilitate bioprocess consolidation. Herein, we reveal our new discovery in elucidating the process of hardwood lignin modification/degradation by clearwing borer, Paranthrene robiniae . The wood-boring clearwing borer, P. robiniae , effectively tunnels hardwood structures during the larval stage; its digestion products from wood components, however, has not yet been investigated. A series of analysis conducted in this study on tunnel walls and frass produced provided evidence of structural alterations and lignin degradation during such hardwood digestion process. The analysis included solid state (13)C cross-polarization magic angle spinning (CP/MAS) nuclear magnetic resonance (NMR) spectroscopy, attenuated total reflectance Fourier transform infrared (ATR-FTIR), pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), and thermogravimetric (TG) analysis; the results strongly suggest that the structural alteration of lignin primarily involved a preferential degradation of syringyl units accompanied by oxidation on the side chains of lignin guaiacyl moieties. This study also further indicated that unlike the wood-feeding termite the clearwing borer does not target cellulose as an energy source, and thus its lignin degradation ability should provide potential information on how to disassemble and utilize hardwood lignin. Overall, this biological model with an efficient lignin disruption system will provide the new insight into novel enzyme system required for effective plant cell wall disintegration for enhanced cellulose accessibility by enzymes and production of value-added lignin derived products.