Aromatic compound degradation by the wood-feeding termite Coptotermes formosanus (Shiraki) Jing Ke, Deepak Singh, Shulin Chen * Department of Biological Systems Engineering, Washington State University, Pullman, WA 99164-6120, USA article info Article history: Received 15 October 2010 Received in revised form 6 December 2010 Accepted 7 December 2010 Available online 17 June 2011 Keywords: Wood-feeding termites (WFT) Ligninolytic enzymes Aromatic compounds Dyes Lignin model monomers and dimers Lignin sulfonate Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) Gut segments abstract Wood-feeding termites (WFT) have proven to be highly efficient for wood digestion. There is evidence to support the hypothesis that there are ligninolytic enzymes existing in the gut of WFT responsible for wood pretreatment toward cellulose utilization. Elucidating the mechanism of biomass pretreatment through lignin modification in termites will help to develop more efficient lignocellulosic biofuel production processes. The in-vivo degradation of aromatic compounds with different substructures, including dyes, lignin model monomers and dimers, and lignin sulfonate, by Coptotermes formosanus (Shiraki) was investigated. The degradation of aromatic compounds was determined using pyrolysis-gas chromatography/mass spectrometry. The results revealed that WFT were able to metabolize the conju- gated aromatic structures and that the degradation efficiency is higher in the foregut and midgut regions than in the hindgut. This is the first time that evidence has been provided to show different aromatic compound degradation in the separate gut segments of a termite. This study provides information on the C. formosanus (Shiraki) lignin modification phenomenon, and it demonstrates that phenomenon’s potential in the breakdown of the plant cell wall. Understanding this lignin modification could contribute to technology that will supplant current harsh pretreatment protocols for plant cell walls and thereby better facilitate the conversion of cellulose and hemicellulose. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Improving the efficiency of lignocellulosic biomass pretreat- ment is essential for economic cellulose hydrolysis and lignocellulosics-based biofuel production (Mosier et al., 2005). Wood-feeding termites (WFT) are created by nature to utilize wood as their sole food source and are capable of efficient wood-cellulose degradation in a matter of hours (utilization of 65%e99% cellulose and hemicellulose in wood within 24 h) (Esenther and Kirk, 1974; Wood, 1978), instead of weeks, as in fungal and bacterial systems (Chen et al., 2010). This makes WFT a promising model organism for biological pretreatment of lignocellulose under natural conditions. Currently, how termites accomplish the rapid wood-cellulose conversion process is at the center of scientific curiosity. Since cellulose and hemicellulose are protected by lignin from being damaged (Chabannes et al., 2001; Böerjan et al., 2003), lignin removal, or at least modification, should be required for wood- cellulose hydrolysis (Lorenz et al., 2009). Brune et al. (1995a), Brune et al. (1995b) found the existence of an oxygen gradient in termite guts and demonstrated it to be a critical co-substrate for degradation of aromatic compounds. By collecting the respired 14 CO 2 after feeding termites on natural and synthetic 14 C labeled lignins and related compounds, Butler and Buckerfield (1979) and Cookson (1987) demonstrated the disruption of synthetic lignin and wood lignin by the WFT. Furthermore, characterization of natural polymeric lignin after WFT digestion, and identification of low-molecular-weight products from wood-lignin disruption (Geib et al., 2008; Ke et al., 2010), have provided considerable insights into the chemistry of lignin modification by WFT. However, the relationship of lignin degradation/modification in different gut compartments of WFT is less understood, as previous studies relied on the overall degradation of synthetic lignin by WFT. We propose the hypothesis that WFT have evolved an efficient lignin modifi- cation process that is dependent on the particular gut compart- ments for further efficient wood-cellulose hydrolysis. Lignin itself is a heterogeneous natural polymer with phenyl- propane chains linked by carbonecarbon and ether bonds (Feldman et al., 1986). The exact chemical structure and specific reactions involved in its biodegradation are not yet clear. The complexity of lignin structure has continually challenged researchers to characterize it prior to and following biological digestion in order to understand the biomass digestion * Corresponding author. Tel.: þ1 509 335 3743; fax: þ1 509 335 2722. E-mail address: chens@wsu.edu (S. Chen). Contents lists available at ScienceDirect International Biodeterioration & Biodegradation journal homepage: www.elsevier.com/locate/ibiod 0964-8305/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.ibiod.2010.12.016 International Biodeterioration & Biodegradation 65 (2011) 744e756