Development of modified HCH-1 kinetic model for long-term enzymatic cellulose hydrolysis and comparison with literature models

Abstract

Background Enzymatic hydrolysis is a major step for cellulosic ethanol production. A thorough understanding of enzymatic hydrolysis is necessary to help design optimal conditions and economical systems. The original HCH-1 (Holtzapple–Caram–Humphrey–1) model is a generalized mechanistic model for enzymatic cellulose hydrolysis, but was previously applied only to the initial rates. In this study, the original HCH-1 model was modified to describe integrated enzymatic cellulose hydrolysis. The relationships between parameters in the HCH-1 model and substrate conversion were investigated. Literature models for long-term (> 48 h) enzymatic hydrolysis were summarized and compared to the modified HCH-1 model. Results A modified HCH-1 model was developed for long-term (> 48 h) enzymatic cellulose hydrolysis. This modified HCH-1 model includes the following additional considerations: (1) relationships between coefficients and substrate conversion, and (2) enzyme stability. Parameter estimation was performed with 10-day experimental data using α-cellulose as substrate. The developed model satisfactorily describes integrated cellulose hydrolysis data taken with various reaction conditions (initial substrate concentration, initial product concentration, enzyme loading, time). Mechanistic (and semi-mechanistic) literature models for long-term enzymatic hydrolysis were compared with the modified HCH-1 model and evaluated by the corrected version of the Akaike information criterion. Comparison results show that the modified HCH-1 model provides the best fit for enzymatic cellulose hydrolysis. Conclusions The HCH-1 model was modified to extend its application to integrated enzymatic hydrolysis; it performed well when predicting 10-day cellulose hydrolysis at various experimental conditions. Comparison with the literature models showed that the modified HCH-1 model provided the best fit. Electronic supplementary material The online version of this article (10.1186/s13068-019-1371-5) contains supplementary material, which is available to authorized users.

Supercritical Fluids: A Promising Technique for Biomass Pretreatment and Fractionation

“…Nonetheless, this original model is only applied to short-term enzymatic hydrolysis that does not consider factors that decrease velocity rates, such as enzyme deactivation by lignin, end-product inhibition and changes in substrate reactivity, accessibility and synergism between enzymes (Bansal et al, 2009). Recently, modifications of HCH-1 model were developed in order to follow longterm enzymatic hydrolysis of cellulose up to 10-day experiment without considering lignin inhibition (Liang et al, 2019). Hence, this assumption was probably supported by the blocking of lignin inhibition by β-glucosidases that are found in excess in the most recent commercial cellulase preparations.…”

Modeling Biowaste Biorefineries: A Review

“…The modified HCH-1 accounts for this influence on the cellulose conversion rate and enzyme stability over longer periods. Its main features are its use of the product binding constant β and the quantification of the number of active sites that are covered by enzymes (E) with the parameter ε (Holtzapple et al, 1984;Liang et al, 2019). The modified long-term HCH-1 model is given by Equation 8:…”

“…It additionally assumes non-competitive inhibition of the enzyme activity by the obtained hydrolysis products, in comparison with the competitive inhibition as used in the Kadam et al (2004) model. The modified HCH-1 model further distinguishes itself from the original model by considering a lumped enzyme mixture (κ is the kinetic constant of the lumped enzyme), making it more closely aligned with reality (Liang et al, 2019).…”

Synthesis of mitomycin analogs catalyzed by coupling of laccase with lipase and the kinetic model

“…A laccase–lipase co‐catalytic system was reported which was used to catalyze the domino reaction between catechols and nucleophilic reagents, which supported a remarkable increase of the yield in comparison with laccase‐alone system . The establishment of kinetic models of multiple enzymatic catalytic cascade processes has been one of the focuses in this field, which can provide insight into the effect of an entire cascade on kinetics, enlarging bioreactor and so on . Deng et al .…”

“…18 The establishment of kinetic models of multiple enzymatic catalytic cascade processes has been one of the focuses in this field, which can provide insight into the effect of an entire cascade on kinetics, enlarging bioreactor and so on. 19,20 Deng et al 21 proposed a semiempirical kinetic model which accurately predicted the hydrolysis performance of laccase-treated wheat straw. A quantitative Ping-Pong bi-bi mechanism model was constructed to simulate and optimize the reaction process.…”