Kinetic Model For Enzymatic Hydrolysis Research Articles

A Novel Kinetic Modeling of Enzymatic Hydrolysis of Sugarcane Bagasse Pretreated by Hydrothermal and Organosolv Processes.

Lignocellulosic biomasses have a complex and compact structure, requiring physical and/or chemical pretreatments to produce glucose before hydrolysis. Mathematical modeling of enzymatic hydrolysis highlights the interactions between cellulases and cellulose, evaluating the factors contributing to reactor scale-up and conversion rates. Furthermore, this study evaluated the influence of two pretreatments (hydrothermal and organosolv) on the kinetics of enzymatic hydrolysis of sugarcane bagasse. The kinetic parameters of the model were estimated using the Pikaia genetic algorithm with data from the experimental profiles of cellulose, cellobiose, glucose, and xylose. The model considered the phenomenon of non-productive adsorption of cellulase on lignin and inhibition of cellulase by xylose. Moreover, it included the behavior of cellulase adsorption on the substrate throughout hydrolysis and kinetic equations for obtaining xylose from xylanase-catalyzed hydrolysis of xylan. The model for both pretreatments was experimentally validated with bagasse concentration at 10% w/v. The Plackett-Burman design identified 17 kinetic parameters as significant in the behavior of process variables. In this way, the modeling and parameter estimation methodology obtained a good fit from the experimental data and a more comprehensive model.

Kinetic Model for Enzymatic Hydrolysis of Cellulose from Pre-Treated Rice Husks

Rice husks contain cellulose as a raw material for manufacturing second-generation bioethanol. Cellulose from pre-treated rice husks was converted into reducing sugars through enzymatic hydrolysis using enzymes derived from Aspergillus niger. This study aims to determine the kinetics of enzymatic hydrolysis at enzyme concentrations of 10, 15, and 20% (v/w) and hydrolysis times of 5, 10, 15, 20, and 25 h. The results showed that cellulose was hydrolyzed to form reducing sugars. The CMCase activity and FPase activity reached 548.940 and 314.892 U mL−1, respectively, much higher than most previous reports on this genus. From the calculation of the reaction rate using the Michaelis–Menten kinetic model, the value of the Michaelis constant ranges from 0.001 to 0.0007, and the maximum rate is 1.3 × 10−7 to 2.7 × 10−7 Mol L−1 s−1. The highest reducing sugar concentration was obtained (1.80 g L−1) at an enzyme concentration of 20% (v/w) and a hydrolysis time of 25 h.

Two-dimensional Simulation of Diffusion and Advection Effects in Enzymatic Hydrolysis of Cellulose

Enzymatic hydrolysis process to transform lignocellulosic cellulose into sugar in a bioreactor tank involves different controlling factors such as advection, diffusion and fragmentation of cellulose chains. Although it has been observed experimentally that enzymatic hydrolysis is strongly influenced by the environmental effects in a tank, these effects have not been adequately quantified. In this work, a current kinetic model for enzymatic hydrolysis of cellulose was extended by coupling the population balance equations (PBE) with advection and diffusion terms to model the spatial evolution of the system. The mathematical model was solved using the DAE-QMOM technique. The aim of this study was to simulate the effect of diffusion and advection on the fragmentation of cellulose chains during enzymatic hydrolysis in two-dimensional domain. This study demonstrated the applicability and usefulness of a commercial software (COMSOL Multiphysics) for finding the solution of PBE-advection-diffusion in cellulosic hydrolysis problem. The key implication of this work is that advection is a significant phenomenon which could increase the number of cellulose particles. Also, diffusion alone cannot increase hydrolysis rate, but the combination of advection and diffusion increases hydrolysis rate.

Kinetic Modeling of Enzymatic Hydrolysis of Pretreated Sorghum Bicolor and Rice Husk

In this study, the hydrolysis of pretreated sorghum stem and rice husk was investigated at various initial enzyme concentrations and substrate loadings. The slowdown in enzymatic hydrolysis of lignocellulosic materials with conversion has often been attributed to decreasing the activity of enzyme. A kinetic model was developed and expressed mathematically based on enzyme deactivation for enzymatic hydrolysis of lignocellulosic materials. The decline in activation of the adsorbed enzyme is represented by a second order reaction. The models were used to fit experimental data of sorghum stem and rice husk hydrolysis. The models basic parameters which can explain the effects observed experimentally were determined and discussed. The model performed well in predicting hydrolysis trends at experimental condition.

One-Dimensional Simulation of Diffusion and Advection Effects in Enzymatic Hydrolysis of Cellulose

Enzymatic hydrolysis process to transform lignocellulosic cellulose into sugar in a bioreactor tank involves different controlling factors such as advection, diffusion and fragmentation of cellulose chains. Although it has been observed experimentally that enzymatic hydrolysis is strongly influenced by the environmental effects in a tank, these effects have not been adequately quantified. In this study, a current kinetic model for enzymatic hydrolysis of cellulose was extended by coupling the Population Balance Equations (PBE) with advection and diffusion terms to model the spatial evolution of the system. The mathematical model was solved using the DAE-QMOM technique. The aim of this study was to simulate the effect of diffusion and advection on the fragmentation of cellulose chains during enzymatic hydrolysis in one-dimensional domain. This study demonstrated the applicability and usefulness of a commercial software (COMSOL Multiphysics) for finding the solution of PBE-advection-diffusion in cellulosic hydrolysis problem. The key implication of this work is that advection is a significant phenomenon which could in-crease the number of cellulose particles. Also, diffusion alone cannot increase hydrolysis rate, but the combination of advection and diffusion increases hydrolysis rate.

Numerical prediction of kinetic model for enzymatic hydrolysis of cellulose using DAE-QMOM approach

Bioethanol production from lignocellulosic biomass consists of three fundamental processes; pre-treatment, enzymatic hydrolysis, and fermentation. In enzymatic hydrolysis phase, the enzymes break the cellulose chains into sugar in the form of cellobiose or glucose. A currently proposed kinetic model for enzymatic hydrolysis of cellulose that uses population balance equation (PBE) mechanism was studied. The complexity of the model due to integrodifferential equations makes it difficult to find the analytical solution. Therefore, we solved the full model of PBE numerically by using DAE-QMOM approach. The computation was carried out using MATLAB software. The numerical results were compared to the asymptotic solution developed in the author's previous paper and the results of Griggs et al. Besides confirming the findings were consistent with those references, some significant characteristics were also captured. The PBE model for enzymatic hydrolysis process can be solved using DAE-QMOM method. Also, an improved understanding of the physical insights of the model was achieved.

A pore‐hindered diffusion and reaction model can help explain the importance of pore size distribution in enzymatic hydrolysis of biomass

Until now, most efforts to improve monosaccharide production from biomass through pretreatment and enzymatic hydrolysis have used empirical optimization rather than employing a rational design process guided by a theory-based modeling framework. For such an approach to be successful a modeling framework that captures the key mechanisms governing the relationship between pretreatment and enzymatic hydrolysis must be developed. In this study, we propose a pore-hindered diffusion and kinetic model for enzymatic hydrolysis of biomass. When compared to data available in the literature, this model accurately predicts the well-known dependence of initial cellulose hydrolysis rates on surface area available to a cellulase-size molecule. Modeling results suggest that, for particles smaller than 5 × 10(-3) cm, a key rate-limiting step is the exposure of previously unexposed cellulose occurring after cellulose on the surface has hydrolyzed, rather than binding or diffusion. However, for larger particles, according to the model, diffusion plays a more significant role. Therefore, the proposed model can be used to design experiments that produce results that are either affected or unaffected by diffusion. Finally, by using pore size distribution data to predict the biomass fraction that is accessible to degradation, this model can be used to predict cellulose hydrolysis with time using only pore size distribution and initial composition data.

Kinetic modeling of enzymatic hydrolysis of pretreated kitchen wastes for enhancing bioethanol production

It is well known that use of low cost and abundant waste materials in microbial fermentations can reduce product costs. Kitchen wastes disposed of in large amounts from cafeterias, restaurants, dining halls, food processing plants, and household kitchens contain high amounts of carbohydrate components such as glucose, starch, and cellulose. Efficient utilization of these sugars is another opportunity to reduce ethanol costs. In this study, the effect of pretreatment methods (hot water, acid solutions, and a control) on enzymatic hydrolysis of kitchen wastes was evaluated using a kinetic modeling approach. Fermentation experiments conducted with and without traditional fermentation nutrients were assessed at constant conditions of pH 4.5 and temperature of 30°C for 48h using commercial dry baker’s yeast, Saccharomyces cerevisiae. The control, which involved no treatment, and hot water treated samples gave close glucose concentrations after 6h. The highest and lowest rates of glucose production were found as 0.644 and 0.128 (h−1) for the control (or no-pretreated (NPT)) and 1% acid solutions, respectively. The fermentation results indicated that final ethanol concentrations are not significantly improved by adding nutrients (17.2–23.3g/L). Thus, it was concluded that product cost can be lowered to a large extent if (1) kitchen wastes are used as a substrate, (2) no fermentation nutrient is used, and (3) hydrolysis time is applied for about 6h. Further optimization study is needed to increase the yield to higher levels.

Kinetic modeling of enzymatic hydrolysis of poplar waste by wet oxidation pretreatment

Kinetic modeling of enzymolysis of pulp fiber waste pretreated by a wet oxidation process was studied. First, a wet oxidation pretreatment of fiber waste was carried out. It was found that hemicellulose were removed efficiently, yielding material with a pentosan content of 4% (based on the o.d. biomass). A statistical kinetic model was developed based on the experimental results of the enzymatic hydrolysis of wet oxidation pretreated material. The model can be described as follows: RSY (reducing sugar yield)=12.48×C0.4261×(1-e-0.2021t) ×100%, an equation that can be used to predict the reducing sugar yield in an enzymolysis process. The RSY by enzymatic loading of 35FPU/g achieved almost the highest yield after 48 h, and there was no significant improvement with further extension of the enzymolysis time. The modeling was validated within the enzymatic loading range of 15 to 35FPU/g and provided a satisfactory interpretation of the experimental data.

Kinetic model for the hydrolysis of sterilized palm press fibre

In this study, a kinetic model for enzymatic hydrolysis of oil palm residues considering the effect of sterilization was proposed and validated. Experiments were performed in batch reactor using palm oil mill effluent (POME) supplemented with sterilized and non-sterilized pressed pericarp fibers (PPF) as substrates. Kinetic parameters were estimated by fitting the experimental data to the models. It was found that the sterilization process as well as the variety in substrate particle size exerted an effect on the apparent rate constant ( k), but no effect on the apparent Michaelis constant ( K M ) and apparent competitive inhibition constant ( K I ). When compared with the experimental data, the kinetic model provided good prediction to the oil palm residues hydrolysis with mean square error less than 10%.

Cellulase deactivation based kinetic modeling of enzymatic hydrolysis of steam-exploded wheat straw

Applying mass action law and quasi-steady-state theory, two cellulase kinetic models namely Eqs. (5) and (8) were developed on the basis of the first and second order reactions of enzyme deactivation, respectively. The two models are compared according to analysis of experimental data from enzymatic hydrolysis steam-exploded wheat straw. Both simulation and prediction results show Eq. (8) has much higher accuracy than Eq. (5). Analysis of initial hydrolysis rate is also in accordance with Eq. (8) and against Eq. (5). Fitted values of k 2 (the rate constant of product formation), k de2 (the rate constant of enzyme deactivation) and K e (the equilibrium constant) determined from Eq. (8) are 0.4732 h −1, 0.4011 L/(h g), and 16.8597 g/L, respectively. The higher the enzyme concentration is, the larger the deactivation rate.

Kinetic modeling of enzymatic hydrolysis of cellulose in differently pretreated fibers from dairy manure

A kinetic model incorporating dynamic adsorption, enzymatic hydrolysis, and product inhibition was developed for enzymatic hydrolysis of differently pretreated fibers from a nitrogen-rich lignocellulosic material-dairy manure. The effects of manure proteins on the enzyme adsorption profile during hydrolysis have been discussed. Enzyme activity, instead of protein concentration, was used to describe the enzymatic hydrolysis in order to avoid the effect of manure protein on enzyme protein analysis. Dynamic enzyme adsorption was modeled based on a Langmiur-type isotherm. A first-order reaction was applied to model the hydrolysis with consideration being given for the product inhibition. The model satisfactorily predicted the behaviors of enzyme adsorption, hydrolysis, and product inhibition for all five sample manure fibers. The reaction conditions were the substrate concentrations of 10-50 g/L, enzyme loadings of 7-150 FPU/g total substrate, and the reaction temperature of 50 degrees C.

A functionally based model for hydrolysis of cellulose by fungal cellulase

A new functionally based kinetic model for enzymatic hydrolysis of pure cellulose by the Trichoderma cellulase system is presented. The model represents the actions of cellobiohydrolases I, cellobiohydrolase II, and endoglucanase I; and incorporates two measurable and physically interpretable substrate parameters: the degree of polymerization (DP) and the fraction of beta-glucosidic bonds accessible to cellulase, F(a) (Zhang and Lynd, 2004). Initial enzyme-limited reaction rates simulated by the model are consistent with several important behaviors reported in the literature, including the effects of substrate characteristics on exoglucanase and endoglucanase activities; the degree of endo/exoglucanase synergy; the endoglucanase partition coefficient on hydrolysis rates; and enzyme loading on relative reaction rates for different substrates. This is the first cellulase kinetic model involving a single set of kinetic parameters that is successfully applied to a variety of cellulosic substrates, and the first that describes more than one behavior associated with enzymatic hydrolysis. The model has potential utility for data accommodation and design of industrial processes, structuring, testing, and extending understanding of cellulase enzyme systems when experimental date are available, and providing guidance for functional design of cellulase systems at a molecular scale. Opportunities to further refine cellulase kinetic models are discussed, including parameters that would benefit from further study.

Kinetic model for enzymatic hydrolysis in reverse micelles

A bound water model is developed for the interpretation of kinetic data of b-galactosidase in reverse micelles. Assessing the kinetic parameters of p-nitrophenyl-b-D-galactopyranoside hydrolysis in aqueous and reverse micellar system reveals that the major effect on hydrolytic rate is owing to the amount of free water in reverse micelles, not the enzyme molecules' structural change.

A kinetic model for pretreated wheat straw saccharification by cellulase

AbstractA kinetic model for enzymatic hydrolysis of pretreated wheat straw able to describe the reaction process considering only macroscopic properties of enzyme and substrate would be useful in reactor design and scale‐up. In this study Michaelis‐Menten equations were used for different reaction schemes to fit experimental results obtained, working with enzyme loads between 5 and 44 i.u. g−1 pretreated straw. Kinetic parameters were obtained by means of an optimization computer program.

Kinetic studies of enzymatic hydrolysis of insoluble cellulose: Derivation of a mechanistic kinetic model

A comprehensive mechanistic kinetic model for enzymatic hydrolysis of insoluble cellulose has been synthesized by combining models for several key aspects which have been derived independent of each other. The model takes into account the major contributing factors: the nature of the enzyme system, the structure of cellulose, and the mode of interaction between the enzyme and cellulose molecules. It consists of a set of simultaneously occurring ordinary differential equations with ten kinetic constants. All of the kinetic constants have been determined independently by carrying out critically designed experiments, and they appear in the comprehensive model without any arbitrary manipulations. The governing equations of the model have been numerically simulated by means of the computer subroutine CSMP III. The model predicts the progress of hydrolysis of cellulose over a wide range of experimental conditions and hydrolysis times reasonably well. The model can even be applied to predict the progress of hydrolysis for intensively pretreated cellulose with a minor adjustment. The applicability of the model for the actual process development is also discussed.

Kinetic studies of enzymatic hydrolysis of insoluble cellulose: Analysis of the initial rates

A study was conducted on the kinetics of enzymatic hydrolysis of pure insoluble cellulose using unpurified culture filtrate Trichoderma reesei, with the emphasis on the initial reaction period. The initial hydrolysis rate and extent of enzyme (soluble protein)adsorption, either apparent or initial, were evaluated under various experimental conditions. It has been found that the various mass-transfer steps do not control the overall hydrolysis rate and that the hydrolysis rate is mainly controlled by the surface reaction step promoted by the adsorbed enzyme. It has also been found that the initial hydrolysis rate strongly depends on the initial extent of soluble protein adsorption and the effectiveness of the adsorbed soluble protein to promote the hydrolysis. The initial extent of soluble protein adsorption, in turn, is related to the initial cellulose concentration, enzyme concentration, and specific surface area of cellulose, whereas the effectiveness of the initially adsorbed soluble protein to promote the derived to interrelate these parameters without resorting to the Michaelis-Menten kinetics. The present result appear to imply that the role of enzyme-substrate complex formation should not be ignored in deriving a mechanistic kinetic model for enzymatic hydrolysis of cellulose.