Reusability of Immobilized Cellulases with Highly Retained Enzyme Activity and their Application for the Hydrolysis of Model Substrates and Lignocellulosic Biomass

Yuko Ikeda, Archana Parasha

Abstract

Enzyme immobilization is a promising approach to reduce enzyme cost in lignocellulose-based biorefining. This paper describes the reusability of immobilized cellulases and examines hydrolysis of various components of lignocellulose and industrial lignocellulosic biomass when using immobilized cellulases. Two different commercial cellulases, previously denoted as Cellulases 1 (C1) and Cellulases 2 (C2), were separately immobilized on nonporous (S1) and porous (S2) silica. Enzyme immobilization was achieved using a simple, cheap, and safe absorption method that maintains high hydrolysis yields by creating a cellulosome-like environment. Here, we show that all immobilized cellulases could be reused for at least 4 cycles while maintaining ≥ 50% of their activity. In fact, systems containing immobilized C1 displayed >40% activity in the 6th cycle, regardless of the silica used. We obtained relatively high-retained enzyme activities when our immobilized cellulases were employed to hydrolyze cellophane paper (60%–78%), phosphoric acid swollen cellulose (72%–79%), a common component of hemicellulose (xylan; 62%– 84%), steam-exploded poplar (41%–62%), and waste office automation paper (34%–48%). Thus, the immobilized cellulase systems used in this study may be industrially feasible as they can be reused while maintaining relatively high levels of enzyme activities. Importantly, we also show that our immobilized cellulase systems can be applied to not only model substrates, but also to industrially produced lignocellulosic biomass.