The Role of Polymeric Micelles on Chemical Changes of Pretreated Corn Stover, Cellulase Structure, and Adsorption

Significance Statement

    In this research, several novel findings were shared as follows. For the first time, the reduction in enzyme secondary structure in the presence of lignocellulosic biomass was shown with FTIR. Polymeric micelles (PMs) were found to improve enzyme activity more than that of Amphiphiles alone. To understand the mechanism of action, microstructure changes in pretreated corn stover, reformation in enzyme secondary structure and its availability in liquid phase were all evaluated in detail using various techniques and shown to be the causes of improved enzyme activity.    

Figure Legend: Sample FTIR peaks associated with surfactants adsorption and imposed chemical changes in microstructure of corn stover pretreated with single screw extrusion

 

The Role of Polymeric Micelles on Chemical Changes of Pretreated Corn Stover, Cellulase Structure, and Adsorption

BioEnergy Research,March 2014, Volume 7, Issue 1, pp 389-407.

Anahita D. Eckard, Kasiviswanathan Muthukumarappan, William Gibbons.

Department of Agricultural and Biosystems Engineering, South Dakota State University, 1400 North Campus Drive, Brookings, SD, 57007, USA and.

Department of Biology & Microbiology, South Dakota State University, 1400 North Campus Drive, Brookings, SD, 57007, USA.

 

 Abstract

 

Enzymatic hydrolysis of lignocellulosic biomass is limited by rapid cellulase deactivation, consequently requiring large amounts of enzyme to maintain acceptable biomass conversion. In this study, a new approach to improve lignocellulose hydrolysis was investigated. Performing enzymatic hydrolysis of corn stover (CS) in the presence of polymeric–surfactant micelles (PMs) was demonstrated to improve hydrolysis yield to a greater extent than using only surfactant micelles. Application of 2 % (w/w) of polyethylene glycol (PEG 6000) with casein, Tween-20, and Triton X-100 at levels above the critical micelle concentrations increased the hydrolysis yield of corn stover containing high-bound lignin (extrusion-pretreated) by up to 87.8, 11.7, and 7.5 %, respectively. These PMs were not effective during enzymatic hydrolysis of biomass lacking lignin (Avicel) or alkali-pretreated CS (7.2 % lignin). The main reasons for the enhanced cellulase activity observed due to PEG-casein, PEG-Tween, and PEG-Triton were enhanced cellulase solubilization; reformation of {Alpha}-helix substructure; and combination of induced cellulase solubilization, {Alpha}-helix reformation, and chemical changes in the microstructure of biomass, respectively. Deformation of the cellulase substructure during hydrolysis of biomass and its subsequent reformation in the presence of surfactants were shown in this study for the first time. Chemical changes in the microstructure of biomass (e.g., lignin side changes, C–O bonds, and amorphous cellulose) were found to be another potential reason for the effectiveness of surfactants when they are incubated at above 6 g/L for 72 h with biomass.

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