Modeling the minimum enzymatic requirements for optimal cellulose conversion
Date
2013-04
Authors
Den Haan, R.
Van Zyl, J. M.
Harms, T. M.
Van Zyl, W. H.
Journal Title
Journal ISSN
Volume Title
Publisher
IoP Publising
Abstract
Hydrolysis of cellulose is achieved by the synergistic action of endoglucanases, exoglucanases
and -glucosidases. Most cellulolytic microorganisms produce a varied array of these
enzymes and the relative roles of the components are not easily defined or quantified. In this
study we have used partially purified cellulases produced heterologously in the yeast
Saccharomyces cerevisiae to increase our understanding of the roles of some of these
components. CBH1 (Cel7), CBH2 (Cel6) and EG2 (Cel5) were separately produced in
recombinant yeast strains, allowing their isolation free of any contaminating cellulolytic
activity. Binary and ternary mixtures of the enzymes at loadings ranging between 3 and
100 mg g-1 Avicel allowed us to illustrate the relative roles of the enzymes and their levels of
synergy. A mathematical model was created to simulate the interactions of these enzymes on
crystalline cellulose, under both isolated and synergistic conditions. Laboratory results from
the various mixtures at a range of loadings of recombinant enzymes allowed refinement of the
mathematical model. The model can further be used to predict the optimal synergistic mixes of
the enzymes. This information can subsequently be applied to help to determine the minimum
protein requirement for complete hydrolysis of cellulose. Such knowledge will be greatly
informative for the design of better enzymatic cocktails or processing organisms for the
conversion of cellulosic biomass to commodity products.
Description
Publication of this article was funded by the Stellenbosch University Open Access Fund.
The original publication is available at http://iopscience.iop.org/1748-9326/
The original publication is available at http://iopscience.iop.org/1748-9326/
Keywords
Cellulose -- Hydrolysis of, Cellulose conversion, Consolidated bioprocessing, Cellobiohydrolase, Endoglucanase
Citation
Den Haan, R., Van Zyl, J. M., Harms, T. M. & Van Zyl, W. H. 2013. Modeling the minimum enzymatic requirements for optimal cellulose conversion. Environmental Research Letters, 8(2), doi:10.1088/1748-9326/8/2/025013.