A kinetic model considering the heterogeneous nature of the enzyme hydrolysis of lignocellulosic materials

Abstract

In this work, a mathematical model is proposed to predict the kinetic behaviour of the enzymatic conversion of various types of lignocellulosic biomass into fermentable sugars. Digestion of the cellulosic polymers is carried out using enzymatic hydrolysis under different conditions. Unlike other kinetic models, published previously for this process, this one considers the heterogeneous nature of the process by which a solid, in the form of small particles, is decomposed to monosaccharides by the action of a diverse set of enzymes in solution. The effect of the particle size on the hydrolysis rate has also been taken into consideration. To assess the model's goodness of fit to any general situation, the experimental data obtained in the hydrolysis of three different lignocellulosic residues have been analysed. Thus, the hydrolysis data of wheat straw, rice husks and exhausted sugar beet pellets have been compared with the theoretical values calculated by the model. The results obtained show that this model predicts the enzyme's hydrolysis of lignocellulosic substrates under different conditions very accurately and it could therefore be used efficiently in the optimization of the hydrolysis processes implemented in the bio-refinery industry. is a lecturer in the Department of Chemical Engineering and Food Technology at the University of Cádiz, with a background in chemistry and a PhD in chemical engineering from the same university. Her research focuses on the use and valorization of agrofood residues and byproducts using solid-state fermentation and submerged culture, the production of hydrolytic enzymes with industrial applications and the production of value-added bioproducts. Cristina MarzoCristina Marzo is a PhD student chemical engineering at the University of Cádiz. She graduated and obtained a master's degree in chemical engineering from the same university. Her research focuses on the valorization of agroindustrial wastes and byproducts with the main objective of obtaining value-added products. The techniques used for this are mainly biological processes, such as enzyme hydrolysis, submerged fermentation and solid-state fermentation.

Conversion of Exhausted Sugar Beet Pulp into Fermentable Sugars from a Biorefinery Approach

“…As seen in Figure 3 A, RS concentration increases rapidly along the first 18 h in all the cases, while afterward the hydrolysis rate is very low. This is a consequence of the two stages (heterogeneous and homogeneous) that form the kinetics involved in the hydrolysis process [ 20 ]. The maximum RS concentration increased from 28.4 to 36.5 g·L −1 and the hydrolysis yield increased from 27.9% to 32.4% as the fermented solid mass rose from 5 to 10 g. Nevertheless, a similar maximum RS concentration was obtained when the fermented solid mass was 15 g (36.7 g·L −1 ) while the hydrolysis yield decreased until 29.7%.…”

“…This parameter combines the maximum amount of sugar produced and the rate of production ( ). The regression coefficient (r 2 ) of the experimental data to the kinetic model of Caro et al [ 20 ] is also shown.…”

“…The enzymatic hydrolysis of lignocellulosic materials into fermentable sugars is carried out by a complex mechanism that involves diverse phenomena such as adsorption, desorption, enzyme deactivation, etc. In this work, the kinetic model proposed by Caro et al [ 20 ] was used to calculate the general kinetic parameters of the enzyme hydrolysis process: the initial reducing sugar concentration (G o ); theoretical maximum RS concentration, which is the final reducing sugar concentration to be theoretically reached at the end of the process (G f ); and the global hydrolysis rate (k h ). All of them have been calculated for each experiment included here by nonlinear regression, using the damped least squares analysis [ 21 ], fitting the experimental data to the equations of the model.…”

Analysis of the product streams obtained on butanosolv pretreatment of draff

“…Furthermore, the viability of the scale-up of technologies to commercial scale can be aided by conditional and economic optimisation of the system via extensive process modelling e.g. models for the enzymatic hydrolysis of lignocellulose such as the modified Holtzapple-Caram-Humphrey-1 kinetic model [6], a kinetic model considering heterogeneity [7] or mathematical modelling. [8] One potential source of biomass for biorefineries is draff, also known as spent grain, which is produced as a by-product from the brewing and distilling industries.…”

Production of Oligosaccharides from Agrofood Wastes

“…The pretreatment of food waste biomass generally produces a size distribution that should be considered as an influential factor over enzymatic hydrolysis. Substrate particle size affects the overall rate of the hydrolysis process [96], given that this size impacts upon the efficiency of the substrate access of the enzymatic mixture, introducing mass transfer limitations in bigger particles. In addition, high solid presence in the reaction medium, an industrial tendency, increases viscosity and also affects the external and the internal mass transfer rate [97,98].…”