Rapid chromatography for evaluating adsorption characteristics of cellulase binding domain mimetics

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 cata- lytic 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 (20degrees to 120degreesC). 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 30degrees. and 120degreesC. Trypan blue, a polyaromatic, planar molecule, was shown to be irreversibly adsorbed to cotton cellulose at temperatures of < 120degreesC 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. (C) 2004 Wiley Periodicals, Inc.