Rapid chromatography for evaluating adsorption characteristics of cellulase binding domain mimetics

Abstract

The cost of cellulolytic enzymes is one barrier to the economic production of fermentable sugars from lignocellulosic biomass for the production of fuels and chemicals. One functional characteristic of cellulolytic enzymes that improves reaction kinetics over mineral acids is a cellulose binding domain that concentrates the catalytic domain to the substrate surface. We have identified maleic acid as an attractive catalytic domain with pK(a) and dicarboxylic acid structure properties that hydrolyze cellulose while producing minimal degradation of the glucose formed. In this study we report results of a rapid chromatographic method to assess the binding characteristics of potential cellulose binding domains for the construction of a synthetic cellulase over a wide range of temperatures (20 degrees to 120 degrees C). Aromatic, planar chemical structures appear to be key indicators of cellulose adsorption. Indole, the side-chain of the amino acid tryptophan, has been shown to reversibly adsorb to cellulose at temperatures between 30 degrees and 120 degrees C. Trypan blue, a polyaromatic, planar molecule, was shown to be irreversibly adsorbed to cotton cellulose at temperatures of <120 degrees C on the time scale of the experiments. These results confirm the importance of hydrophobic cellulose and the cellulose-binding component of cellulolytic enzymes and cellulolytic enzyme mimetics.

Biomimetic Catalysis for Hemicellulose Hydrolysis in Corn Stover

“…To investigate different catalytic behavior on xylose degradation, equal molar concentration (50 mM) maleic acid (pH 1.9) and sulfuric acid (pH 1.4) in aqueous solution were compared as the model hydrolytic environment for xylose degradation. The starting xylose concentration in solution was 10 g/L, and xylose and furfural concentration at different time points (15,30, and 60 min) and different temperatures (150, 160, and 170°C) were collected and measured by HPLC. Thus, experimental data for estimating the rate of xylose disappearance in the acidic solutions were collected at an initial xylose concentration of 10 g/L over the entire temperature range.…”

“…Developments in the understandings of the structure and catalytic mechanism of natural hemicellulases systems (22)(23)(24), as well as rapid progress in biomimetic chemistry (25)(26)(27), make it possible to achieve this goal. The concept of an enzyme mimetic for lignocellulosics hydrolysis has been revisited by Mosier et al (28)(29)(30). One important observation was that dicarboxylic acids have superior selectivity for the hydrolysis of polymers of -(1,4)-glycolic bonds in cellobiose and microcrystalline cellulose (Avicel) when compared to sulfuric acid, due to the decreased ability to cause glucose degradation.…”

Bioinspired Cellulase-Mimetic Solid Acid Catalysts for Cellulose Hydrolysis

“…Inspired by the hydrophobic interaction mechanism between cellulose and the CBD of cellulase, Mosier et al screened amino acids that could bind cellulose. Indoles and tryptophan blue that have aromatic moieties were found to have high affinities to cellulose ( Mosier et al, 2004 ), which highly indicates that hydrophobic interactions are essential for cellulose-cellulase binding other than hydrogen bonding interactions. Consistently, a variety of carbon materials demonstrate high adsorption capacity for cellulose via hydrophobic interactions ( Chung et al, 2012 ; Chung et al, 2015 ; Onda et al, 2008 ; Yabushita et al, 2016 ).…”

Preparation of Core-Shell Structure Magnetic Carbon-Based Solid Acid and its Catalytic Performance on Hemicellulose in Corncobs

“…Acid can corrode equipment and requires neutralization treatment after the reaction (Mosier et al 2004). As for the enzymes, their high price, low reaction efficiency, and difficulties with recovery restrict their large-scale use (Wood and McCrae 1986;Lu and Mosier 2007).…”