Predominant contribution of an endogenous cellulase to the cellulolysis in the digestive system of grub of banana pseudostem weevil, Odoiporus longicollis (Coleoptera: Curculionidae)

Abstract

Insects have evolved with effective strategies to utilize cellulose as energy source by possessing novel cellulolytic enzymes which can be used as an optimal resource in the bioenergy sector. The study was aimed for evaluating the cellulolytic enzyme in the grub gut of banana pseudostem weevil, Odoiporus longicollis Olivier (Coleoptera: Curculionidae). Primarily, cellulase activity was localized in the gut system, in which the midgut showed the highest activity. The optimum temperature and thermo-tolerance of cellulase activity were found to be 60°C, and was stable at a pH between 5 and 6. Various concentrations of divalent cations (CaCl2, MgCl2, and CuCl2) have differential enhancing and inhibitory effects on cellulase activity. The cellulase was purified using anion exchange chromatography. The specific activity of purified cellulase was 1190.46 U mg− 1. The molecular weight of the cellulase was determined to be 47 kDa. The physicochemical parameters of purified enzyme were similar to that of enzyme activity of crude extract. Mass spectrometry results identified this cellulase was of GHF5 family. The gut microbial cellulase activity as exogenous source showed no competence comparatively.