Analysis of the conversion of cellulose present in lignocellulosic biomass for biofuel production

ROBERTO, JAQUELINE A.; COSTA JÚNIOR, ESLY F. DA; COSTA, ANDRÉA O.S. DA

doi:10.1590/0001-3765202320220635

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ENGINEERING SCIENCES • An. Acad. Bras. Ciênc. 95 (3) • 2023 • https://doi.org/10.1590/0001-3765202320220635 copy

Analysis of the conversion of cellulose present in lignocellulosic biomass for biofuel production

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Among the steps for the conversion of biomass into bioenergy, there is enzymatic hydrolysis. However, factors such as composition, formation of inhibitors, inhibition and enzymatic deactivation can affect the yield and productivity of this process. Lignocellulosic biomass is composed of cellulose, hemicellulose and lignin. However, lignin is organized in a complex and non-uniform way, promotes biomass recalcitrance, which repress the enzymatic attack on cellulose to be converted into glucose, and, consequently, the production of biofuel. Thus, a challenge in enzymatic hydrolysis is to model the reaction behavior. In this context, this study aims to evaluate the performance in enzymatic hydrolysis for the conversion of cellulose present in sugarcane bagasse into glucose. Therefore, modeling and optimization will be proposed to produce high glucose concentration rates. Therefore, a previously developed study will be used, in which the authors proposed a kinetic model for the hydrolysis step. However, as a differential to what has been proposed, the calculation will be carried out evaluating the evaporation, in order to maximize the response to the glucose concentration. Thus, considering evaporation and optimized kinetic parameters, it was possible to obtain high rates of glucose concentration at 204.23 $g.L^{-1

Key words
Biomass; bioethanol; enzymatic hydrolysis; kinetic model

Chemical composition of bagasse	Pre-treated bagasse
Cellulose	70.12%
Hemicellulose	3.79%
Lignin	19.32%
Ashes	4.25%

Operating conditions	Reference values
Humidity $(%)$	82
% Cellulose	0.7
Reactor volume (L)	0.2
Temperature ( $° C$ )	50
Initial reaction volume in the reactor (L)	0.05
Initial substrate concentration $(g . L^{- 1})$	44.44
Initial enzyme concentration ${(F P U . L^{- 1})}^{*}$	842.4

Kinetic parameters	Variables considered for the optimization, obtained by Cavalcanti-Montaño et al. 2013CAVALCANTI-MONTAÑO ID, SUAREZ CAG, RODRÍGUEZ-ZÚÑIGA UF, GIORDANO RLC, GIORDANO RC & DE SOUSA JÚNIOR R. 2013. Optimal bioreactor operational policies for the enzymatic hydrolysis of sugarcane bagasse. Bioenerg Res 6: 776-785.	Optimized parameters in this work
$K$	0.112 $g . L^{- 1} . {min}^{- 1}$	0.214 $g . L^{- 1} . {min}^{- 1}$
$K_{m}$	15.0 $g . L^{- 1}$	40.8 $g . L^{- 1}$
$K_{i}$	4.5 $g . L^{- 1}$	3.1 $g . L^{- 1}$

Objective	Model Description	Feedstock	Results	Reference

Objective	Model Description	Feedstock	Results	Reference
Describe the yield of fermentable sugars, glucose and xylose in the enzymatic hydrolysis step.	They developed a kinetic model based on the Michaelis-Menten theory and an enzymatic deactivation model. Then, they determined empirical equations for the conversion of glucan to glucose and conversion of xylan to xylose.	Bagasse pre-treated with hot water, hydrochloric acid (HCl) and sodium hydroxide (NaOH).	They concluded that the combination of models allowed a high precision of fit to the experimental data, for enzymatic hydrolysis by different compositions of pre-treated bagasse, in addition to providing the analysis of the yield in the pre-treatment step.	Zhang et al. 2021ZHANG Y, ZHANG Y, SONG M, TOPAKAS E, YU Q, YUAN Z, WANG Z & GUO Y. 2021c. Combining Michaelis-Menten theory and enzyme deactivation reactions for the kinetic study of enzymatic hydrolysis by different pretreated sugarcane bagasse. Process Biochem 105: 72-78.
Describe the enzymatic hydrolysis rate, analyzing the nature and intensity of two pretreatments.	They proposed a kinetic model to analyze the nature and intensity of two pretreatments. Thus, they defined the equation for reaction rate and apparent kinetic constant. Those equation were composed by factors of intensity of pretreatment, the accessibility of the enzyme to the substrate and reactivity.	Wheat straw, corn husk and thistle stalks. These biomasses were pretreated with dilute sulfuric acid and ethanol-water.	They concluded that the kinetic model describes the experimental results obtained in the enzymatic hydrolysis for the three raw materials used in the study, in different operating conditions. In addition, wheat straw was the most reactive and thistle stalk the most recalcitrance.	Wojtusik et al. 2020WOJTUSIK M, VERGARA P, VILLAR JC, LADERO M & GARCÍA-OCHOA F. 2020. Enzymatic hydrolysis of several pretreated lignocellulosic biomasses: fractal kinetic modelling. Bioresource Technol 318: 124050.
They developed a kinetic model for the enzymatic hydrolysis reaction in a reactor, considering the fluid dynamics and the transport of solids and dissolved species.	Implementation of equations for fluid transport (substrate and enzyme), equation to determine the substrate concentration; enzyme concentration, taking into account the adsorption of the enzyme to cellulose.	Cellulose substrate.	They concluded that the proposed model perfectly predicted the conversion mechanisms that occur in enzymatic hydrolysis. In addition, the model provided fidelity to capture the substrate gradients within the reactor.	Sitaraman et al. 2019SINGH P, SINGARI RM & MISHRA R. 2022. A review of study on modeling and simulation of additive manufacturing processes. Mater Today: Proc 56: 3594-3603.
Describe the process of fed-batch hydrolysis for a wide range of solids content. In addition, optimization to determine the operating conditions in the fed-batch enzymatic hydrolysis step.	They proposed a kinetic model composed by empirical equations to determine the modified inhibition constant, reaction rate (involves Michaelis-Menten model with product inhibition) and developed mass balances for the concentration of cellulose and glucose.	Hydrothermally pre-treated bagasse (HB) and bagasse pre-treated with diluted and delignified acid (ADB).	They observed that the kinetic model fits the experimental data, mainly for the loading of solids 5, 15 and 20% $w . v^{- 1}$ . Furthermore, it was possible to achieve high sugar levels for both substrates, at 131.24 $g . L^{- 1}$ for HB and 131.46 $g . L^{- 1}$ ADB. They also noticed that the reaction yield for the HB substrate decreased from 67.56% to 65-63%, due to the inhibition of the product. As for the ADB substrate, the yield reduced from 66.16% to 55-52 %.	Godoy et al. 2019EDGAR TF, HIMMELBLAU DM & LASDON LS. 2001. Optimization of chemical processes. 2nd ed. New York: McGraw-Hill Higher, 186 p.
Analyzing the saccharification of cellulose to glucose concentration in a novel fed-batch horizontal bioreactor.	They used the kinetic model proposed by Zhang et al. 2010ZHANG B, ZHAN B & BAO J. 2021a. Reframing biorefinery processing chain of corn fiber for cellulosic ethanol production. Ind Crop Prod 170: 113791., to describe glucose production. Thus, they considered in the model cellulase deactivation as first and second order reaction.	Hydrothermally pre-treated agave bagasse.	The model presented a good fit to the experimental data, for a horizontal bioreactor operating in fed-batch. For the experimental test and simulation, the best glucose concentration obtained was the solids load at 25% having 195.60 $g . L^{- 1}$ of glucose. Working in fed batch, 30% solids load for a horizontal bioreactor, glucose concentrations of approximately 120 $g . L^{- 1}$ can be reached.	Pino et al. 2019NANDA S & BERRUTI F. 2021. A technical review of bioenergy and resource recovery from municipal solid waste. J Hazard Mater 403: 123970.
Show a model applicable for fed-batch hydrolysis, aiming at high substrate concentration.	It was developed two models, one simplified and one complete model. The simplified model includes only the enzymatic adsorption and the first-order reaction of the enzyme-substrate complex. The complete model involves competitive glucose inhibition and decreasing rate factors related to substrate and enzyme behavior.	Filter paper.	The solids concentration ranged from 5 to 50 $g . L^{- 1}$ . In experimental tests, they obtained glucose concentrations up to 100 $g . L^{- 1}$ . On the other hand, for the complete model that presented the best fit, they found results below 40 $g . L^{- 1}$ , for an initial solids concentration of 30 $g . L^{- 1}$ .	Tervasmäki et al. 2017TERVASMÄKI P, SOTANIEMI V, KANGAS J, TASKILA S, OJAMO H & TANSKANEN J. 2017. A discretized model for enzymatic hydrolysis of cellulose in a fed-batch process. Bioresource Technol 227: 112-124.
Describe the enzymatic hydrolysis in high solid concentration.	They used kinetic model by Kadam et al. 2004GU T, WANG B, ZHANG Z, WANG Z, CHONG G, MA C, TANG YJ & HE Y. 2019. Sequential pretreatment of bamboo shoot shell and biosynthesis of ethyl (R)-4-chloro-3-hydroxybutanoate in aqueous-butyl acetate media. Process Biochem 80: 112-118.. The proposed model is based on the biochemistry of enzymatic hydrolysis and includes enzymatic adsorption, product inhibition, substrate reactivity and conversion of hemicellulose to xylose. However, it neglects thermal and mechanical enzymatic inactivation.	Sugarcane straw pre-treated with hot water.	The model presented a reasonable fit to the experimental data with solids load of 10-20%, enzyme feed between (5-60 $F P U . g^{- 1}$ ), being possible to obtain glucose concentrations up to approximately 110 $g . L^{- 1}$ .	Angarita et al. 2015ANGARITA J, SOUZA R, CRUZ A, BISCAIA JR E & SECCHI A. 2015. Kinetic modeling for enzymatic hydrolysis of pretreated sugarcane straw. Biochem Eng J 104: 10-19.
They developed a dynamic model for the simultaneous feeding of substrate and enzyme, with the purpose of reaching high concentrations of glucose, in the process of enzymatic hydrolysis in a reactor operating in fed batch.	They determined the mass balances for volume, substrate and product. In addition, they considered the equation for the reaction rate, from the Michaelis-Menten equation with inhibition by the product (glucose). They proposed an equation for substrate and enzyme feeding.	Bagasse pre-treated by steam explosion and delignified with 4% NaOH.	From the simulation, it was noticed that it was necessary to feed in three pulses of enzyme for the analyzed system. Furthermore, it was possible to reach glucose concentrations of 160 $g . L^{- 1}$ and, in the experimental tests for model validation, product concentration of 200 $g . L^{- 1}$ .	Cavalcanti- Montaño et al. (2013)

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[1] Correspondence to: Jaqueline Alves Roberto E-mail: jaqueline.alvesroberto@gmail.com