No 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.

Insects have evolved with effectual strategies to utilise cellulose substrates for the energy source and can be used as an optimal resource in the field of bioenergy sector and insect-pest management by finding the novel cellulolytic enzymes from it. The present study was aimed at evaluating the endogenous cellulolytic system in the larval gut of banana pseudostem weevil Odoiporus longicollis. Initially, the cellulase activity was localized in the gut system in which the midgut showed highest activity of 2858 U min-1mg-1. The optimum temperature and thermal stability were found to be 60°C at the highest activity of 2712 U min-1mg-1. The enzyme was stable at a pH from 5 to 6. The effect of various divalent cations tested on the cellulase activity showed a differential enhancing and inhibitory activity upon varying concentrations. Purification of cellulase was carried out using anion exchange chromatography with the DEAE-Sepharose CL-6B matrix which was chosen according to the results of the batch assay. The total and specific activity of purified cellulase was 1166 U min-1mg-1 and 1190.46 U min-1mg-1, respectively, with 41.66 % recovery of activity. The molecular weight of the purified cellulase was determined as 47 kDa. The optimum temperature for the purified enzyme was 60°C with an activity of 1130 U min-1mg-1. The purified fraction had the highest activity between pH 5 and 6. Kinetic parameters of the purified cellulase enzyme were determined in which Km and Vmax values were 1.03 mg/ml and 343 U min-1mg-1, respectively. Mass spectrometry result identified the homology towards endoglucanase sequence belonging to the GHF5 family. The gut microbial cellulase activity showed no competence comparatively.

No abstract

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.