Synergistic effect of ionic liquid and surfactant for enzymatic hydrolysis of lignocellulose by Paenibacillus sp. LLZ1 cellulase

Abstract

Stable cellulases are critical for in situ hydrolysis of ionic liquid-pretreated lignocellulose, and surfactants were reported to improve the stability of cellulase in practical circumstances. In this study, synergistic effect of Tween-80 and [Emim]OAc was first identified to enhance the hydrolysis of lignocellulose by Paenibacillus sp. LLZ1 cellulase, proving the effectiveness of surfactants in in situ hydrolysis. Protein fluorescence and near-UV circular dichroism spectroscopy analyses illustrated that ionic liquids might move local residues and alter global tertiary structure of cellulase, leading to higher instability. The addition of Tween-80 might turn the microenvironment of cellulase residues more hydrophilic and reduce the contact of protein with deactivation factors. The synergistic system was further applied in the in situ hydrolysis of microcrystalline cellulose and bagasse cellulose by Paenibacillus cellulase. The enzymatic hydrolysis rate of microcrystalline cellulose was enhanced by 2.5-fold and the final conversion was improved by 45%. Scanning electron microscopy demonstrated the substrate solubilizing effect during reaction by monitoring the morphological changes of lignocellulosic substrates. This study highlighted the potential of applying synergistic reaction system in in situ enzymatic hydrolysis of lignocellulose, and revealed the inherent mechanism initially.