Saccharification of Agricultural Lignocellulose Feedstocks and Protein-Level Responses by a Termite Gut-Microbe Bioreactor

Abstract

This study investigated saccharification and protein-level responses to the candidate biofuel feedstocks corn stover (CS) and soybean residue (SR) by the gut of a lower termite. The focus termite was Reticulitermes flavipes, which is a highly efficient digester of wood lignocellulose that houses a mixture of prokaryotic and eukaryotic microbes in its gut. Our specific objectives were to (i) measure saccharification potential of the CS and SR feedstocks by termite gut protein extracts, (ii) identify specific proteins in the termite gut responding to feeding on CS and SR diets, and (iii) evaluate gut lignocellulase and accessory enzyme activity responses to CS and SR feeding. Cellulose paper was the control diet. Although CS was saccharified at higher levels, termite gut protein extracts saccharified both CS and SR irrespective of feedstock loading. Consumption of the CS and SR feedstocks by termites resulted in surprisingly few differences in gut protein profiles, with the main exception being elevated myosin abundance with SR feeding. Activity of potential lignocellulases and accessory enzymes was generally similar between CS and SR fed guts as well; however, cellobiohydrolase/exoglucanase activity was higher with CS feeding and glutathione peroxidase activity with SR feeding. These findings have significance from two perspectives. First, SR feeding/digestion appears to cause physiological stress in the termite gut that likely would extend to other types of microbial environments including those within industrial bioreactors. Second, because termites can survive on exclusive CS and SR diets and their guts exhibit clear CS and SR saccharification activity, this validates the R. flavipes system as a potential source for CS and SR degrading enzymes; in particular, cellobiohydrolases/exoglucanases and glutathione peroxidases from this system may play roles in CS and SR breakdown.

Screening of Phytophagous and Xylophagous Insects Guts Microbiota Abilities to Degrade Lignocellulose in Bioreactor

“…Little information is available concerning implementation and taming of insect guts microbiomes as a whole in bioreactors. Some articles related to utilization of termite guts protein extracts ( Rajarapu and Scharf, 2017 ) or microbiomes as a whole ( Hamdi et al, 1992 ; Auer et al, 2017 ) but to our knowledge no information could be found concerning other type of insects implemented in bioreactors.…”

The promising future of microalgae: current status, challenges, and optimization of a sustainable and renewable industry for biofuels, feed, and other products

“…Depending on the purpose of pretreatment, chemical, biological, thermochemical, or thermophysical methods are used, sometimes in combination [ 105 , 106 ]. After lysis of the cells the macromolecules of sugars need saccharification which mean to break the α-(1 → 4), α-(1 → 6), β-(1 → 3) and β-(1 → 6) glycosidic linkages between the monomers to release the monomers units [ 107 ]. Lignocellulose present in the biomass impedes the pretreatment process, as this material is recalcitrant to conversion.…”

A Century of Synergy in Termite Symbiosis Research: Linking the Past with New Genomic Insights

“…These findings were covered extensively in several recent reviews (11-13, 36, 112-114, 151). This topic is thus not covered further in this review; however, some key recent advances relating to novel symbiont sequencing protocols and feedstock digestion have been reported (81,97,104,105).…”