Varied lignin disruption mechanisms for different biomass substrates in lower termite

Abstract

Termites are highly effective in degrading lignocellulosics thus can be used as economic model biological systems for studying plant cell wall degradation. Comparative study on lignin disruption mechanisms for hardwood, barley straw and softwood (previously established results) along the gut of wood-feeding lower termite Coptotermes formosanus (Shiraki) was successfully conducted with the aid of advanced analytical techniques of pyrolysis gas chromatography mass spectrometry (Py-GC/MS). The results strongly suggested that besides the softwood, the lower termites are also able to digest the hardwood and barley straw. For both lignocellulosics, termite induced specific lignin modifications, respectively, resulting in increased lignin solubility. However, the corresponding in-situ lignin disruption mechanisms varied for different biomass substrates with varied lignin structures of guaiacyl softwood and syringyl-guaiacyl hardwood/barley straw lignins. As a result, the related lignolytic enzyme system induced modifications on both guaiacyl and syringyl-guaiacyl lignin structures respectively in softwood and hardwood, but no such significant modification on barley straw; indicating the semi-specification of termite-origin lignolytic enzymes for selected lignin chemical bonds and functional groups. This phenomenon could be potentially utilized for customization of different treatment processes for different types of biomass with varied lignin structures.