Evaluation of Cellulolytic Endo-1,4-B-D-Glucanase Activity in the Digestive Fluid of Adult Phytophagous Beetle Hoplasoma unicolor

Mohammad Mosleh Mohammad Mosleh Uddin,Yeasmin Yeasmin Zahan,Newton Newton Kar,Babamale Abdulkareem Babamale Abdulkareem Olarewaju,Suzana Afrin Suzana Afrin Lima,Tanim Jabid Tanim Jabid Hossain

doi:10.21315/tlsr2021.32.3.4

Abstract

Insects of the taxonomic order Coleoptera are recognised for considerable cellulolytic activity in their digestive fluid. The cellulolytic activity of the gut fluid in Hoplasoma unicolor, a member of Coleoptera, however, remains unexplored. In this study, we, for the first time, report the qualitative and quantitative analysis of cellulolytic activity in the digestive fluid of this insect. The cellulolytic endo-1,4-β-D-glucanase activity was confirmed in the supernatant of the insect’s digestive fluid by agar plate assay using carboxymethyl cellulose as the substrate. To determine the optimum pH, enzyme activity was further assessed in an acidic pH range of 5 to 6, and the highest activity was observed at pH 5.3. For quantitative analysis, endoglucanase activity was measured using 3,5-dinitrosalicylic acid method which revealed that the specific activity of the gut sample was 0.69 (±0.01) units per mg of protein. For further characterisation of the cellulases in the sample, SDS-PAGE and zymogram analysis were carried out. Two active cellulolytic bands were detected on the zymogram suggesting the presence of two distinct endoglucanases which completely disappeared upon heating the sample at 55°C. Our study, therefore, highlights prospect of the gut fluid of H. unicolor as an important source of cellulase enzymes that merits further investigations into their extensive characterisation for potential industrial applications.

Highlights

Cellulases are hydrolytic enzymes that catalyse the cleavage of 1,4-β-glycosidic bonds between glucose residues present in cellulose, the most abundant biopolymer produced on earth and the major constituent of agricultural and industrial wastes (Bayer et al 1998; Dashtban et al 2010)
This study investigated cellulolytic activity in the gut fluid of the beetle H. unicolor
This work aimed at assessing the endo-1,4-β-D-glucanase activity in digestive fluid of the phytophagous beetle H. unicolor

Summary

Introduction

Cellulases are hydrolytic enzymes that catalyse the cleavage of 1,4-β-glycosidic bonds between glucose residues present in cellulose, the most abundant biopolymer produced on earth and the major constituent of agricultural and industrial wastes (Bayer et al 1998; Dashtban et al 2010). The cellulase enzymes refer to three distinct types of cellulolytic hydrolases, e.g., endo-1,4-β-D-glucanase (endoglucanase; EC 3.2.1.4), exo-1,4-β-D-glucanase (cellobiohydrolase; EC 3.2.1.91 and 3.2.1.176), and β-glucosidase (EC 3.2.1.21) (Okano et al 2014). Whereas β-glucosidases catalyse the final step: hydrolysis of the products generated by both endo- and exo-glucanases, i.e., soluble cellulodextrins and cellobioses to produce glucose. Complete degradation of cellulose into glucose requires synergistic action among the three hydrolases, endoglucanase is believed to be the most important of the three (Annamalai et al 2016). These cellulolytic hydrolases are commonly referred to as carboxymethylcellulase or CMCase, since carboxymethylcellulose (CMC) is the substrate most widely used for the determination of functional cellulase activity in experimental procedures (Ali et al 1995)

Objectives

Methods

Results

Conclusion