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

Insects have evolved with effective strategies to utilize cellulose as an energy source by possessing cellulolytic enzymes which can be used as an optimal resource in the bioenergy sector. The study was aimed at evaluating the cellulolytic enzyme in the larval gut of the banana pseudostem weevil, Odoiporus longicollis Olivier (Coleoptera: Curculionidae). Primarily, cellulase activity was localized along the gut, in which the midgut showed the highest activity (2858 U/mg). The thermo‐tolerance of cellulase activity was found to be up to 80°C (highest at 60°C), and the enzyme 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 (OlCel) was purified using anion exchange chromatography. The molecular weight of the cellulase was determined to be 47 kDa. The physicochemical parameters of the purified enzyme were similar to that of enzyme activity of whole gut extract. Mass spectrometry results identified sequence similarities of purified cellulase to the glycosyl hydrolase family 5 (GHF5) family. The gut microbial cellulase activity as exogenous source showed no competence compared with the endogenous activity. The outcome of the study provided insights into the efficient cellulolytic system in the digestive tract of banana pseudostem borer Odoiporus longicollis. The results suggested that the endogenous cellulase possibly belonging to glycosyl hydrolase family 5 (GHF5) plays a major role in cellulolysis compared with its exogenous counterpart. Highlights Determination of endogenous cellulase activity in Odoiporus longicollis. The gut cellulase activity was one of the highest in insects reported to date. Purified cellulase (OlCel) was highly thermo‐tolerant and exhibited homology to glycosyl hydrolase family 5 (GHF5) of beetles and fungus.