Binding modules alter the activity of chimeric cellulases: Effects of biomass pretreatment and enzyme source

Authors

  • Tae-Wan Kim,

    1. Energy Biosciences Institute, University of California, Berkeley, California 94720; telephone: +1-510-642-2408; fax: +1-510-643-1228
    Search for more papers by this author
  • Harshal A. Chokhawala,

    1. Energy Biosciences Institute, University of California, Berkeley, California 94720; telephone: +1-510-642-2408; fax: +1-510-643-1228
    Search for more papers by this author
  • Dana Nadler,

    1. Department of Chemical Engineering, University of California, Berkeley, California
    Search for more papers by this author
  • Harvey W. Blanch,

    1. Energy Biosciences Institute, University of California, Berkeley, California 94720; telephone: +1-510-642-2408; fax: +1-510-643-1228
    2. Department of Chemical Engineering, University of California, Berkeley, California
    Search for more papers by this author
  • Douglas S. Clark

    Corresponding author
    1. Energy Biosciences Institute, University of California, Berkeley, California 94720; telephone: +1-510-642-2408; fax: +1-510-643-1228
    2. Department of Chemical Engineering, University of California, Berkeley, California
    • Energy Biosciences Institute, University of California, Berkeley, California 94720; telephone: +1-510-642-2408; fax: +1-510-643-1228.
    Search for more papers by this author

  • Tae-Wan Kim and Harshal A. Chokhawala contributed equally to this work.

Abstract

Improving the catalytic activity of cellulases requires screening variants against solid substrates. Expressing cellulases in microbial hosts is time-consuming, can be cellulase specific, and often leads to inactive forms and/or low yields. These limitations have been obstacles for improving cellulases in a high-throughput manner. We have developed a cell-free expression system and used it to express 54 chimeric bacterial and archaeal endoglucanases (EGs), with and without cellulose binding modules (CBMs) at either the N- or C-terminus, in active enzyme yields of 100–350 µg/mL. The platform was employed to systematically study the role of CBMs in cellulose hydrolysis toward a variety of natural and pretreated solid substrates, including ionic-liquid pretreated Miscanthus and AFEX-pretreated corn stover. Adding a CBM generally increased activity against crystalline Avicel, whereas for pretreated substrates the effect of CBM addition depended on the source of cellulase. The cell-free expression platform can thus provide insights into cellulase structure-function relationships for any substrate, and constitutes a powerful discovery tool for evaluating or engineering cellulolytic enzymes for biofuels production. Biotechnol. Bioeng. 2010;107:601–611. © 2010 Wiley Periodicals, Inc.

Ancillary