Saccharification of agricultural lignocellulosic feedstocks by endogenous and symbiotic cellulases from the subterranean termites

Abstract

This study investigated the protein fraction-level in vitro and in vivo saccharification potential by the guts of two geographically different lower termites’ species Reticulitermes flavipes and Heterotermes indicola using biofuel producing feedstocks sugarcane bagasse, pinewood, cottonwood, corn stover, and rice husk. The gut protein extract from both termite species saccharified all lignocellulose material regardless of feedstock loading. However, R. flavipes showed significantly (p < 0.05) higher saccharification potential than H. indicola. Consumption of the sugarcane bagasse, pinewood, and corn stover was maximum by R. flavipes, whereas H. indicola exposed cottonwood and sugarcane feedstocks as the most palatable food source with 100% survivability. This study also hypothesized that feeding on various feedstocks will show variable impacts on enzyme activities. An adaptive mechanism enables the termites and their endosymbionts for optimized consumption of variable food sources. Results supported "diet adaptation" hypothesis by indicating β-glucosidase, exoglucanase, and xylanase activities, which were significantly the highest for sugarcane bagasse, pinewood, and cottonwood to rice husk and control diets in both termite species. These results are important in physiological changes in termites that lead to gut microbial environment changes and 100% survivability on exclusive sugarcane bagasse, pinewood, and cottonwood feedstocks. Both termite species' guts exhibit the clear saccharification for all feedstocks, which validate the H indicola and R. flavipes systems as a potential source for lignocellulose biomass digesting enzymes particularly β-glucosidase, endoglucanase, exoglucanase, and xylanases.