Computer-Assisted Rational Modifications to Improve the Thermostability of β-Glucosidase from Penicillium piceum H16

Abstract

β-Glucosidase plays key role in the saccharification of cellulosic biomass. The use of β-glucosidase would benefit from improvements in its thermostability in some industrial applications. In this work, two rational computer-aided strategies were devised to enhance the thermostability of a highly active β-glucosidase from Penicillium piceum H16. Single-point mutants were proposed based on the proline theory. The effects of the mutation on protein stability were further predicted using molecular dynamics (MD) simulations. The optimal single mutant, G305P, was found to provide a 20.0 % improvement in thermostability. Then computer-assisted virtual saturated mutation was first used to select the optimal triple mutations which would further increase the thermostability of β-glucosidase by the Calculate Mutation Energy/Stability module of Discovery Studio (DS) 4.0. The triple mutant, S507F/Q512W/S514W, provided a 46.3 % improvement in thermostability. A detailed structural analysis showed that the additional hydrophobic interactions played decisive roles in the improvement in thermostability, and the use of mutants with enhanced stability may benefit formulation of more effective enzyme cocktails for lignocellulosic bioconversion.