Changes in the Phenolic Fraction of Protobind 1000 and Bacterial Microbiota in the Gut of a Higher Termite, Nasutitermes Ephratae

Termites are examples of natural biomass utilization systems that have evolved to overcome the recalcitrance of lignin to degradation. To investigate the application of this to the conversion of technical lignins produced by biorefineries, a higher wood-feeding termite species, Nasutitermes ephratae, was fed with a commercial grass soda lignin (Protobind 1000, PB1000). We investigated the fate of PB1000 in termite guts and the changes in gut microbiota that occurred using Pyrolysis - Gas Chromatography / Mass Spectrometry (Py-GC/MS) and high-throughput sequencing of the 16S rRNA genes. The worker caste termites fed with PB1000 had only half the survival rate of the controls and increased the PB1000 syringyl/guaiacyl ratio from 1.74 to 2.26. The changes in the syringyl/guaiacyl ratio were consistent with the degradation of the free phenolic monomers in PB1000 inside the termite gut, and they were associated with the increase in the relative abundance of Firmicutes and Bacteroidetes. This work showed the ability of the digestive tract of a wood-feeding higher termite species, N. ephratae, to metabolize the free-volatile phenolic monomers in PB1000. Overall, our results identified bacterial candidates for the development of a bacterial inoculum in pretreatment processes for the utilization of technical lignin in biorefineries.