Background:
Termites are highly effective in lignocelluloses degradation thus can be used as model for studying plant cell wall degradation in biological systems. However, the process of lignin deconstruction and/or degradation in termite is still not well understood.
Results:
We have investigated the associated structural modification by termite in the lignin biomolecular assembly in softwood tissues critical for cell wall degradation. Comparative studies on the termite digested (termite feces) and native (control) softwood tissues with the aid of advanced analytical techniques; such as, 13C cross polarization magic angle spinning (CP/MAS) nuclear magnetic resonance (NMR) spectroscopy, pyrolysis gas chromatography mass spectrometry (Py-GC/MS), and flash pyrolysis in presence of tetramethylammonium hydroxide (TMAH) were conducted. The 13C CP/MAS NMR spectroscopic analysis revealed elevated level of guaiacyl derived (G unit) polymeric frame work in the termite digested softwood (feces), while providing specific evidence of cellulose degradation. The Py-GC/MS data were in agreement with the 13C CP/MAS NMR spectroscopic studies, thus indicated dehydroxylation and modification of selective intermonomer side-chain linkages in the lignin proper in the termite feces. Moreover, Py (TMAH)-GC/MS analysis revealed significant differences in the product distribution between control and termite feces. This strongly suggests that the structural modification in lignin proper could be associated with the formation of additional condensed inter-unit linkages.
Conclusion:
Collectively, these data further establish: (1) the conservation of the major beta-O-4' (beta-aryl ether), albeit with sub-structure degeneracy, and (2) the nature of resulting polymer in termite feces retained most of its original aromatic moieties (G unit derived). Overall, these results provide insight into lignin unlocking mechanisms for understanding plant cell wall deconstruction towards development of new enzymatic pretreatment processes mimicking termite system for biochemical conversion of lignocellulosic biomass to fuels and chemicals.