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Cellulase digestibility of pretreated biomass is limited by cellulose accessibility
Author(s) -
Jeoh Tina,
Ishizawa Claudia I.,
Davis Mark F.,
Himmel Michael E.,
Adney William S.,
Johnson David K.
Publication year - 2007
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.21408
Subject(s) - cellulase , trichoderma reesei , cellulose , cellulosic ethanol , corn stover , chemistry , biomass (ecology) , food science , lignin , substrate (aquarium) , crystallinity , enzymatic hydrolysis , beta glucosidase , hydrolysis , biochemistry , pulp and paper industry , organic chemistry , agronomy , biology , ecology , engineering , crystallography
Attempts to correlate the physical and chemical properties of biomass to its susceptibility to enzyme digestion are often inconclusive or contradictory depending on variables such as the type of substrate, the pretreatment conditions and measurement techniques. In this study, we present a direct method for measuring the key factors governing cellulose digestibility in a biomass sample by directly probing cellulase binding and activity using a purified cellobiohydrolase (Cel7A) from Trichoderma reesei . Fluorescence‐labeled T. reesei Cel7A was used to assay pretreated corn stover samples and pure cellulosic substrates to identify barriers to accessibility by this important component of cellulase preparations. The results showed cellulose conversion improved when T. reesei Cel7A bound in higher concentrations, indicating that the enzyme had greater access to the substrate. Factors such as the pretreatment severity, drying after pretreatment, and cellulose crystallinity were found to directly impact enzyme accessibility. This study provides direct evidence to support the notion that the best pretreatment schemes for rendering biomass more digestible to cellobiohydrolase enzymes are those that improve access to the cellulose in biomass cell walls, as well as those able to reduce the crystallinity of cell wall cellulose. Biotechnol. Bioeng. 2007; 98: 112–122. © 2007 Wiley Periodicals, Inc.