Study of the Difference between Enzyme Adsorption onto Hydrotropic and Alkali Lignin Separated from Eucalyptus and Bamboo

Abstract

Enzymatic hydrolysis of lignocellulosic biomass is the key step for controlling the cost of bioethanol production. However, the non-productive adsorption of cellulase onto lignin in biomass severely hampers the enzyme activity and hydrolysis efficiency. Thus, understanding the adsorption mechanism of cellulase onto lignin is critical for the development of enzyme mixtures and enzymatic hydrolysis. In this investigation, cellulase, β-glucosidase (BG), and xylanase adsorption onto lignin from eucalyptus and bamboo, extracted by alkali and hydrotropic techniques, were compared. The physico-chemical properties of the four types of isolated lignin were detected. Langmuir isotherms were used to interpret the cellulase adsorption kinetics of the lignin. The hydrophobicity was found to be the major factor that affected the cellulase adsorption affinity of lignin. The surface charge was important for the adsorption of BG and xylanase onto the lignin. A comparison was made between hydrotropic and alkali lignin, and the hydrotropic lignin from eucalyptus had the highest cellulase adsorption capacity and lowest BG and xylanase adsorption capacities.