Enzymaticin situsaccharification of rice straw in aqueous-ionic liquid media using encapsulatedTrichoderma aureoviridecellulase

Abstract

BACKGROUND Enzymatic in situ saccharification of lignocellulose in ionic liquids (ILs) has become a hot topic of research, but is hampered by the incompatibility of ILs with cellulase. The aim of this present work was to improve IL tolerance of the cellulase from Trichoderma aureoviride strain HS through an efficient encapsulation method, and thus to develop a compatible IL–cellulase system for biorefining. RESULTS The cellulase was encapsulated in alginate beads and its stability was greatly enhanced in various concentrations of 1-ethyl-3-methylimidazolium dimethylphosphate ([Emim][DMP]). The encapsulated cellulase preserved 76% of the original activity in 40% (v/v) [Emim][DMP] for 12 h, whereas free cellulase lost nearly 95% activity. After treating rice straw with [Emim][DMP] at 100 °C and dilution to a final IL concentration of 40% (v/v), the pretreatment slurry was in situ hydrolyzed using encapsulated cellulase. Under the one-pot process, a maximum saccharification rate of 84% was obtained, increased by 65% compared with that in buffer based on free cellulase. CONCLUSION The hydrophilic alginate hydrogel protected the hydration shell of cellulase well against destruction by [Emim][DMP]. The feasibility of hydrolysis reaction in aqueous-IL media using encapsulated cellulase was demonstrated, thus developing a one-pot, wash-free scheme for saccharification of lignocellulose. © 2014 Society of Chemical Industry