A technical soda lignin as sole carbon-diet for a higher termite species, Nasutitermes ephratae: insight into the changes in the gut bacterial community and in the lignin phenolic fraction

BackgroundTermites account for natural biomass utilization systems (NBUS) that evolved the ability to overcome the overall recalcitrance of lignins towards lignocellulose transformation processes. With the objective of applying this capacity 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). The survival rates of Protobind 1000-fed termites were determined as well as changes in the structure of gut bacterial community and in the chemical composition of this technical lignin. ResultsThe ingestion of PB1000 by worker castes of N. ephratae was revealed by Pyrolysis-Gas Chromatography Mass Spectrometry (Py-GC/MS) analyses directly performed on termites. Survival rates were reduced by two –fold in the termites fed with PB1000 compared to controls. The relative abundance of Firmicutes and Bacteroidetes increased in the gut bacterial community of termites fed with PB1000. The digestion of PB1000 by termites triggered an increase in the syringyl-to-guaiacyl (S/G) ratios. These changes in the chemical composition of PB1000 in the gut of termites was marked by a decrease in relative content of free phenolic monomers.ConclusionThis work showed the abilities of digestive tract of a wood-feeding higher termite species, N. ephratae to metabolize the fraction of the volatile phenolic monomers of PB1000. Overall, our results provide insights into the bacterial lineage candidates for development of bacterial inoculum for pretreatment processes in valorization of technical lignin in biorefinery.