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Cellulose hydrolysis in evolving substrate morphologies III: Time‐scale analysis
Author(s) -
Zhou Wen,
Xu Ying,
Schüttler HeinzBernd
Publication year - 2010
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.22814
Subject(s) - substrate (aquarium) , cellulose , hydrolysis , chemistry , embedding , enzymatic hydrolysis , cellulosic ethanol , scale (ratio) , depolymerization , biological system , stereochemistry , chemical engineering , polymer chemistry , organic chemistry , physics , computer science , oceanography , quantum mechanics , artificial intelligence , biology , geology , engineering
Abstract We present a time‐scale analysis for the enzymatic hydrolysis of solid cellulosic substrates, based on our recently developed kinetic model (Zhou et al., 2009a, Biotechnol Bioeng 104:261–274; Zhou et al., 2009b, Biotechnol Bioeng 104:275–289) which incorporates both enzymatic chain fragmentation and hydrolytic time evolution of the solid substrate morphology. Analytical order‐of‐magnitude estimates of the relevant single‐layer chain depolymerization times are first discussed. These time‐scale estimates for pure and mixed enzyme systems can be employed to calculate the degree of synergy between endo ‐ and exo ‐acting enzymes in a mixed enzyme system. By the way of a quasi‐steady‐state approximation which allows for a greatly simplified analytical solution of the model, we also explain the origin and give order‐of‐magnitude estimates of the two characteristic hydrolysis time scales which arise in this model when the solid substrate morphology is taken into account. These analytically derived time‐scale relations explain how the embedding of cellulose chains in a solid substrate acts as a crucial rate‐limiting factor and results in a substantial slowing down of the hydrolytic conversion process, compared to a hypothetical substrate of immediately enzyme‐accessible, isolated chains. The analytical time‐scale results are verified by numerical simulations and compared to experimental observations. Biotechnol. Bioeng. 2010;107: 224–234. © 2010 Wiley Periodicals, Inc.