Location: Healthy Processed Foods ResearchTitle: Investigation of adsorption kinetics and isotherm of cellulase and B-Glucosidase on lignocellulosic substrates Author
|Zheng, Yi - CLEMSON UNIVERSITY|
|Zhang, Ruihong - UNIVERSITY OF CALIFORNIA|
Submitted to: Biomass and Bioenergy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/25/2016
Publication Date: 5/6/2016
Citation: Zheng, Y., Zhang, R., Pan, Z. 2016. Investigation of adsorption kinetics and isotherm of cellulase and B-Glucosidase on lignocellulosic substrates. Biomass and Bioenergy. 91:1-9.
Interpretive Summary: This study revealed that cellulose had much higher adsorption capacity and affinity for cellulase than for B-glucosidase. Cellulase adsorbed quickly on Avicel, and then was released into solution as hydrolysis proceeded. Since lignin can adsorb cellulase non-specifically and irreversibly, the cellulase was not released back to solution after the cellulose of the pretreated CWR was hydrolyzed into soluble sugars. As a result, pCWR adsorption capacity and affinity for cellulase were much higher than Avicel. All adsorption isotherms of both B-glucosidase and cellulase on Avicel, pretreated CWR and lignin numerically obey the Langmuir isotherm.
Technical Abstract: Clear understanding of enzyme adsorption during enzymatic hydrolysis of lignocellulosic biomass is essential to enhance the cost-efficiency of hydrolysis. However, conclusions from literatures often contradicted each other because enzyme adsorption is enzyme, biomass/pretreatment and experimental condition specific, which makes descriptions and modeling of enzyme-substrate interaction difficult and inconsistent from case to case. This study investigated adsorption kinetics and isotherm under actual hydrolysis conditions with commercial cellulase and ß-glucosidase on Avicel, dilute acid pretreated Creeping Wild Ryegrass (pCWR) and lignin residue of pCWR after enzymatic hydrolysis. It was found that B-glucosidase has little affinity to Avicel, but significant affinity to dilute acid pCWR and lignin with maximum adsorption capacity (Emax) of 161.57 and 173.50 mg protein/g-substrate, respectively. During hydrolysis, adsorption of cellulase on Avicel was productive and reversible (Emax=22.86 mg protein/g-substrate); however, nonproductive and irreversible adsorption of cellulase on pCWR (Emax=42.55 mg protein/g-substrate) and lignin (Emax=86.07 mg protein/g-substrate) became significant and resulted in cellulase deactivation. Lignin is a key issue causing high cost of enzymatic hydrolysis of lignocellulosic biomass. The nonionic surfactant, Tween 20 was found to significantly overcome nonproductive adsorption of cellulase and B-glucosidase on lignin by reducing the adsorption affinity. All adsorption data including with and without Tween 20 were fit well to Langmuir isotherm.