Improvement of saccharification of native grass, Pennisetum sp. using cellulase from isolated Aspergillus fumigatus for bioethanol production: an insight into in silico molecular modelling, docking and dynamics studies

Abstract

Lignocellulosic grass biomass is potential substrate for economical and sustainable bioethanol production. However, the processing cost of bioethanol that majorly includes the hydrolysis of cellulose by cellulases is still a major concern for its industrial production. Thus, knowledge on the sequence to the structural study of cellulase enzyme with consideration of its catalytic region can give important information for effective enzyme engineering and consequently towards enhanced bioethanol production from Pennisetum sp. Therefore, in this study, sequence conservativeness of different cellulosic site among a group of endoglucanase family of cellulase from previously isolated Aspergillus species has been determined. Furthermore, comparative molecular modeling of the endoglucanase from eight different Aspergillus species including Aspergillus fumigatus was conducted and the obtained structures revealed a high degree of difference in their conformational folds. Analysis from InterProScan revealed that the modeled endoglucanase has similar types of domains and share homology with protein family, such as glycoside hydrolase family-61 and fungal cellulose binding domain. Furthermore, molecular docking and interaction studies demonstrated the presence of residues in the endoglucanase of A. fumigatus viz. His20, His88, Asp96, Ala99, Ser100, Ser101, His102, His169, Glu170, Arg173, Glu178, and Tyr218 that are responsible in forming the substrate interaction. An interesting molecular phenomenon, i.e., catalytic promiscuity has been noted for all the substrate bound complexes of A. fumigatus endoglucanase which also depicts the degree of ligand binding efficacy of the studied enzyme. The molecular interaction study, binding energy analysis and molecular dynamics simulation, demonstrated that heteromeric substrate XylGlc3 is more strongly interacting with the receptor enzyme. Overall, the present findings revealed that important amino acid residues can help in increasing the specificity of endoglucanase from A. fumigatus towards hydrolysis of Pennisetum sp. and other biomass that has an adequate amount of XylGlc3, for possible industrial applications.