Effect of nonionic surfactant PEG on lignocellulose enzymatic hydrolysis of cotton stalk

In order to improve the cellulose hydrolysis, reducing the amount of enzyme, the effect of different degree ploymerization poly ethylene glycol (PEG, with various amount of ethylene oxide) on the enzymatic hydrolysis of cotton stalk was investigated, especially with regard to soluble reducing sugar, enzyme activity, enzyme protein adsorption, degradation rate, and enzyme kinetics parameters. The results showed that addition 2.5 g/L of PEG2000, 4000, 6000, 8000 binded to lignin by hydrophobic interaction and hydrogen bonding, reduced the unproductive binding of enzymes, in which PEG6000 was the best. Addition of 3.0 g/L of PEG6000 to enzyme hydrolysis of lignocellulose increased the conversion rate from 28.13% to 58.12% with 24 h hydrolysis time. Adsorption of enzyme protein content decreased from78.72% to 45.17%. By addition of PEG6000 it was possible to perform hydrolysis in 3 h. FPA (filter paper activity) decreased from 0.1245 to 0.012 FPU/mL, and descended by 90.37% without PEG6000. FPA was recovered from 0.012 to 0.041 FPU/mL with PEG6000. With 48 h hydrolysis, conversion rate with and without PEG6000 addition reached 65.71% and 54.68%, respectively, which was improved by 18%. PEG6000 addition can improve the cotton stalk lignocellulose hydrolysis rate, and the results can provide a reference for the industrial production of cotton stalk.