BACKGROUND: Lignocellulose is a large source of biomass. However, the conversion ratio of lignocellulose into fermentable sugars is quite low, and the saccharification process requires lots of enzyme. In order to improve biocatalysis efficiency of cellulase for lignocellulose, poly ethylene glycol (PEG4000) is added to the above process. The effect of the order of addition of PEG4000 and cellulase on lignocellulose saccharification processes, and the interaction between PEG4000 and eocellobiohydrolase I (CBH I) were investigated by DNS, UV absorption spectra and Fourier transform infrared (FTIR) spectroscopy. RESULTS: Results show that different orders of addition of PEG4000 and cellulase have a strong influence on the saccharification process, and both orders of addition can improve the saccharification rate. In particular, the addition of PEG4000 before cellulase can reduce wasteful cellulase adsorption on the lignin, and the saccharification rate of lignocellulose can be significantly improved. Without corn stover (substrate) in the saccharification process, examinations by UV absorption spectra and FTIR demonstrate that the interactions between PEG4000 and CBH I are hydrogen bonds and hydrophobic interaction. In addition, it is found that the activity of CBH I is decreased with increasing interaction time and the amount of the PEG4000 added in the saccharification process. CONCLUSION: The addition of PEG4000 before cellulase to lignocellulose saccharification processes is a reasonable way to improve the saccharification rate of lignocellulose. (C) 2010 Society of Chemical Industry