N-terminal PEGylated cellulase: a high stability enzyme in 1-butyl-3-methylimidazolium chloride

Abstract

A new approach to improve cellulase stability in 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]), based on covalently binding the N-terminal α-amino acid residue of commercial cellulase to mPEG-ALD (monomethoxyl-polyethylene glycol aldehyde), is proposed. N-terminal PEGylated cellulase (Cell-ALD) was obtained by using mPEG-ALD as a modifier and by controlling the reaction pH in the range of 4–5. The stability of Cell-ALD was first studied in different concentrations of [Bmim][Cl] at 50 °C and 80 °C. The thermal stability of Cell-ALD was obviously enhanced, and was affected by the molecular weight of mPEG-ALD and the degree of modification (DM). mPEG-ALD 5k (an average molecular weight of 5000 Daltons) increased the stability of the enzyme at 50 °C by more than 30 times compared with the unmodified cellulase in 25% [Bmim][Cl] which behaves as a powerful enzyme deactivating agent. Thus, a stabilized Cell-ALD has been successfully used for the saccharification of dissolved cellulose in [Bmim][Cl] (i.e. up to 95% hydrolysis in 24 h) at 50 °C.