Acid Pretreatment Of Lignocellulosic Biomass Research Articles

Prediction of phenolic compounds and glucose content from dilute inorganic acid pretreatment of lignocellulosic biomass using artificial neural network modeling

Dilute inorganic acids hydrolysis is one of the most promising pretreatment strategies with high recovery of fermentable sugars and low cost for sustainable production of biofuels and chemicals from lignocellulosic biomass. The diverse phenolics derived from lignin degradation during pretreatment are the main inhibitors for enzymatic hydrolysis and fermentation. However, the content features of derived phenolics and produced glucose under different conditions are still unclear due to the highly non-linear characteristic of biomass pretreatment. Here, an artificial neural network (ANN) model was developed for simultaneous prediction of the derived phenolic contents (CPhe) and glucose yield (CGlc) in corn stover hydrolysate before microbial fermentation by integrating dilute acid pretreatment and enzymatic hydrolysis. Six processing parameters including inorganic acid concentration (CIA), pretreatment temperature (T), residence time (t), solid-to-liquid ratio (RSL), kinds of inorganic acids (kIA), and enzyme loading dosage (E) were used as input variables. The CPhe and CGlc were set as the two output variables. An optimized topology structure of 6–12-2 in the ANN model was determined by comparing root means square errors, which has a better prediction efficiency for CPhe (R2 = 0.904) and CGlc (R2 = 0.906). Additionally, the relative importance of six input variables on CPhe and CGlc was firstly calculated by the Garson equation with net weight matrixes. The results indicated that CIA had strong effects (22%-23%) on CPhe or CGlc, then followed by E and T. In conclusion, the findings provide new insights into the sustainable development and inverse optimization of biorefinery process from ANN modeling perspectives.Graphical

Statistical optimization of dilute acid pretreatment of lignocellulosic biomass by response surface methodology to obtain fermentable sugars for bioethanol production

Central composite design to optimize sugar recovery from cotton straw and sunflower straw using dilute acid pretreatment was applied. Selected input variables were acid concentration, retention time, and temperature, as well as the response parameter of sugar yield. The optimum pretreatment conditions observed for maximum sugar yield are temperature: 121.7°C, acid concentration: 2.28% (vol/vol), and time: 36.82 minutes for cotton straw; temperature: 87.03°C, and acid concentration: 3.68% (vol/vol), and time: 36.82 minutes for sunflower straw. Maximum sugar concentrations were corresponded to 20 and 17.5 g L−1 under conditions for sunflower and cotton straw, respectively. This study not only investigates the sugar recovery efficiency statistically but also examines the ethanol production efficiency. As a result, the maximum ethanol concentration, ethanol yield, and ethanol productivity of 7.21 g L−1, 0.41 g g−1, and 0.10 g L−1 h−1 for cotton straw and 8.05 g L−1, 0.40 g g−1, and 0.11 g L−1 h−1 for sunflower straw were achieved via fermentation with Saccharomyces cerevisiae, respectively. The output of this study is important for the commercialization of bioprocesses that enable the conversion of the lignocellulosic waste matrix into high value-added products in a biorefinery concept.

Valorizing waste liquor from dilute acid pretreatment of lignocellulosic biomass by Bacillus megaterium B-10

Dilute acid pretreatment liquor (DAPL) of lignocellulose contains abundant waste sugar resource for further upgrade. But the inhibitors, produced from sugar dehydrogenation, impedes the waste sugar valorization. In this study, an efficient biostrategy was developed to upgrade the waste sugar in DAPL. The concentration of sugar and phenolics in DAPL reached 19.61 g/L and 0.57 g/L, respectively, after pretreatment of rice straw with 0.5 % (v/v) sulfuric acid for 40 min at 121 °C. Bacillus megaterium B-10 could tolerate the furfural toxicity products in DAPL and convert the waste sugar into high-valuable products, polyhydroxyalkanoate (PHA). This polymer was characterized by GC–MS and 1H-NMR, and the as-synthesized PHA was identified as poly-3-hydroxybutyrate (PHB), a typical PHA. A demonstrated yield of PHB (1.496 g/L) was achieved, which accounted for 32.56 % of dry cell weight. Moreover, characterizations of PHB demonstrated that the biosynthetic PHB exhibited favorable thermoplastic properties. This bioconversion of B-10 provides an efficient strategy not only for waste pollution treatment, but also for lignocellulose valorization.

Production of bioethanol and xylitol from non-detoxified corn cob via a two-stage fermentation strategy

A novel two-stage fermentation strategy was applied to produce xylitol and ethanol from the whole acid-pretreated corn cob slurry. The acid-pretreated corn cob was used without filtration and detoxification by the two-stage fermentation with the robust Kluyveromyces marxianus CICC 1727-5. In the first stage, xylose in the slurry after dilute acid pretreatment of lignocellulosic biomass was used to produce xylitol under micro-aeration conditions. In the second stage, simultaneous saccharification fermentation was carried out, and the ethanol was produced from glucose releasing from the solid. Important parameters, such as aeration rate, cellulase loading during xylose utilization and SSF fermentation were studied for best performance. The two-stage fermentation strategy removed the inhibition of glucose on xylose, and little xylose was left in the fermentation broth. Under the optimized condition, the maximum ethanol and xylitol concentration were 52 g/L and 24.2 g/L corresponding to the yield of 0.41 g/g and 0.82 g/g, respectively.

Ferrous and Ferric Ion-Facilitated Dilute Acid Pretreatment of Lignocellulosic Biomass under Anaerobic or Aerobic Conditions: Observations of Fe Valence Interchange and the Role of Fenton Reaction.

Ferrous ion co-catalyst enhancement of dilute-acid (DA) pretreatment of biomass is a promising technology for increasing the release of sugars from recalcitrant lignocellulosic biomass. However, due to the reductive status of ferrous ion and its susceptibility to oxidation with exposure to atmosphere, its effective application presumably requires anaerobic aqueous conditions created by nitrogen gas-purging, which adds extra costs. The objective of this study was to assess the effectiveness of oxidative iron ion, (i.e., ferric ion) as a co-catalyst in DA pretreatment of biomass, using an anaerobic chamber to strictly control exposure to oxygen during setup and post-pretreatment analyses. Remarkably, the ferric ions were found to be as efficient as ferrous ions in enhancing sugar release during DA pretreatment of biomass, which may be attributed to the observation that a major portion of the initial ferric ions were converted to ferrous during pretreatment. Furthermore, the detection of hydrogen peroxide in the liquors after DA/Fe ion pretreatment suggests that Fenton reaction chemistry was likely involved in DA/Fe ion pretreatments of biomass, contributing to the observed ferric and ferrous interchanges during pretreatment. These results help define the extent and specification requirements for applying iron ions as co-catalysts in DA pretreatments of biomass.

Acid – treated activated carbon for phenolic compound removal in acid pre-treatment of lignocellulosic biomass for biogas production

Phenolic compound can be an inhibitor during acid pre-treatment process in the conversion of biomass into bioenergy and consequently reduces the production yield. Thus, this study aimed to investigate the potential use of activated carbon from coconut shell for phenolic compound removal and gallic acid was used as model phenolic. Granular activated carbon was treated by using 20% concentration of phosphoric acid to its properties and function. Acid treated and untreated activated carbon were characterized in term of morphology, surface functionalities and material phase by means of SEM, FT-IR and XRD. Few parameters that influenced the removal of gallic acid were studied which included the effect of adsorbent dosage, initial concentration, contact time, and pH. It is observed that the acid treated activated carbon was successfully remove the gallic acid for about 97% using of 0.5g/L adsorbent dosage, with initial concentration of 100 mg/L, at pH value of 4 and 150 minutes contact time. The adsorption behavior was fixed with Langmuir isotherm fixed the experiment data which indicates homogenous adsorption. These experimental results also revealed that coconut shell based activated carbon is viable cheaper adsorbent for phenolic compound removal.

Pretreatment Ethanol From Cellulosic

<p><strong>Abstract.</strong> Pre-treatment is an important tool for practical cellulose conversion processes and can be carried out in different ways such as mechanical pre-treatment, steam explosion, ammonia fiber explosion, supercritical CO2 treatment, alkali or acid pretreatment, ozone pre-treatment, physicochemical pretreatment, dilute-acid pretreatment and biological pre-treatment. Biomass pretreatment with hot water (HW) is the most investigated physicochemical method use the differences in the thermal stabilities of the major components of lignocellulosic materials. Acid pretreatment of lignocellulosic biomass aims at increasing the sugar substrate digestibility, defined as the concentration of reducing sugars after the hydrolysis, by microorganisms. Acid hydrolysis is an attractive pretreatment method as the hemicellulose degradation runs with the efficiency of approximately 20-90%, depending on the process conditions. Dilute acid (DA) processes with continued research and development, no significant breakthroughs have been made to raise the glucose yields much higher than 65-70%. Acid pretreatment is much more effective than water and alkaline pretreatment in terms of cellulose accessibility increase compared with DA and HW pretreatment.</p><p> </p><p><strong>Keywords:</strong> ethanol, cellulosic, pre-treatment</p>

Acid pretreatment of lignocellulosic biomass for energy vectors production: A review focused on operational conditions and techno-economic assessment for bioethanol production

The acid pretreatment process is the most employed technique used to disrupt the lignocellulosic matrix. Thus, this paper provides an overview of the acid pretreatment considering important aspects related to the operation conditions, yields, future improvements and the potential use to upgrade lignocellulosic biomass in energy vectors. Moreover, this paper is focused on technical and economic aspects of the use of the acid pretreatment in bioethanol production using olive tree biomass as a case study. This review will provide the framework of the acid pretreatment based on reported applications, experimental and theoretical data. The most well-studied applications of the acid pretreatment are in bioethanol and biogas production. Furthermore, this pretreatment has been improved using solid catalysts and by increasing the solids loading. These options have advantages compared to the traditional way. Even so, improvements in the technical and energy aspects must be performed to make the implementation of this process viable from an economic and environmental perspective. Instead, the kinetic modelling and statistical analysis of the acid pretreatment can be postulated as strong tools to predict the behaviour of different feedstocks under acidic conditions. Moreover, new alternatives to increase the mass and heat transfer in this process related to reactor design conform a new research field. Regarding the case study, the acid pretreatment is one of the most energy-consuming stages of bioethanol production. Low solids loadings are recommended to obtain production costs that are comparable with those reported on the industrial level. In contrast, a high solids loading allows the environmental impact of the process to be reduced in terms of liquid waste generation and carbon dioxide emissions. Finally, the acid pretreatment should be included as an effective method for the biotechnological conversion of lignocellulosic biomass to produce energy vectors once the technical, economic and environmental drawbacks have been overcome.

Deterministic and stochastic optimization of dilute acid pretreatment of sugarcane bagasse

Dilute acid pretreatment of lignocellulosic biomass depolymerizes xylan into xylose and lignin into acid-soluble lignin (ASL). Xylose is a desired product, while the lignin fraction can be reduced by producing ASL, since lignin is a non-competitive inhibitor for enzymatic hydrolysis. The optimal conditions for depolymerization of xylan into xylose and lignin into ASL differ during acid pretreatment of bagasse. Hence, multi-objective optimization problems (MOOPs) were formulated for a batch reactor considering temperature as the decision variable. Two different MOOP studies, namely maximization of the weighted sum of final xylose and ASL yields, and minimization of weighted deviation of final xylose and ASL yields around a targeted value, were considered. The optimal temperature varied between 143.2 °C and 113.1 °C along the Pareto front for static optimization. The batch time minimization problem reduced batch time by 32% to achieve desired xylose yield. Dynamic optimization provided minimal benefits over static optimization. Stochastic optimization considering expected uncertainties showed that uncertainties in kinetic parameters impacted results selectively. The optimal temperature decreased by 10 °C for ± 15% variability in kinetic parameters for ASL yield maximization, while it changed marginally for xylose yield maximization. Stochastic optimization showed benefits over static optimization for large variability in kinetic parameters.

Assisted Single-Step Acid Pretreatment Process for Enhanced Delignification of Rice Straw for Bioethanol Production

Dilute acid pretreatment of lignocellulosic biomass at higher temperatures (>160 °C) solubilizes/removes hemicelluloses (xylan, arabinan, mannan, galactan) and acid-soluble lignin (ASL), but, it does not remove acid-insoluble lignin (AIL). During acid pretreatment, the condensation and redeposition of coalesced lignin over cellulose fibers reduces the access of cellulose to cellulases. For higher delignification, various multistage pretreatments are available, however, all these are energy/chemical intensive methods. Therefore, an effective pretreatment which provides increased cellulose accessibility by enhanced removal of hemicelluloses and lignin in a single-step would be preferred. Our investigation reports a novel assisted single-step acid pretreatment (ASAP) process for enhanced delignification of biomass under acidic conditions. Pretreatment of rice straw (particle size of 20 mm) with H2SO4 (0.75% v/v) + boric acid (1% w/v) + glycerol (0.5% v/v) (solid/liquid (S/L), 1:5) at 150 °C for 20 min remove...

Bacteria-enhanced dilute acid pretreatment of lignocellulosic biomass

Pretreatment is indispensable for the large-scale and low-cost bio-products production from lignocellulosic biomass. Herein, a new bacteria-enhanced dilute acid pretreatment (BE-DAP) strategy was introduced. Cupriavidus basilensis B-8 as a potential bacterium for lignin degradation was employed. Multi-scale characterizations on the physicochemical structure of rice straw indicated that Cupriavidus basilensis B-8 could act on the lignin droplets formed in dilute acid pretreatment (DAP), and dig out these droplets to recover cracks and holes on rice straw surface, leaving an opened and porous structure for the easy access of enzyme to inner cellulose. Eventually, the enzymatic digestibility of RS was increased by 35–70% and 173–244% in BE-DAP compared to DAP pretreated and untreated RS, respectively. The BE-DAP strategy, as well as its physicochemical mechanism, opened new perspectives for lignocellulose pretreatment.

Enhancement of hydrogen production by optimization of pH adjustment and separation conditions following dilute acid pretreatment of lignocellulosic biomass

Biorefinery is the integration of various conversion and separation unit processes of biomass to energy, among other products. Downstream processes link these unit processes; however, these are often overlooked to affect energy yield. In this study, use of different alkaline agents and separation techniques, and order of operations, was assessed after conversion of processed sugar into hydrogen through dark fermentation. pH was adjusted to pH 6 using various basic agents; and vacuum filtration and centrifugation were performed to facilitate separation. Sugar loss of 7–40% due to the downstream processes was recorded; however, optimization of the processes ensured high volume and sugar recovery and low degradation byproduct production. Satisfactory volume recovery with high sugar and low byproduct concentrations were achieved after vacuum filtration and pH adjustment with aqueous base. H2 yield and production rate significantly increased after performing the downstream processes. Peak H2 production rate and yield were 1824 mL H2 L−1 d−1 and 1.27 mol H2 mol−1 sugar, respectively, for the optimum condition of vacuum filtration, followed by pH adjustment using 8 N Ca(OH)2.

Physicochemical characterization, modelling and optimization of ultrasono-assisted acid pretreatment of two Pennisetum sp. using Taguchi and artificial neural networking for enhanced delignification

Acid as well as ultrasono-assisted acid pretreatment of lignocellulosic biomass of two Pennisetum sp.; Denanath grass (DG) and Hybrid Napier grass (HNG) have been investigated for enhanced delignification and maximum exposure of cellulose for production of bioethanol. Screening of pretreatment with different acids such as H2SO4, HCl, H3PO4 and H2NO3 were optimized for different temperature, soaking time and acid concentrations using Taguchi orthogonal array and the data obtained were statistically validated using artificial neural networking. HCl was found to be the most effective acid for pretreatment of both the Pennisetum sp. The optimized conditions of HCl pretreatment were acid concentration of 1% and 1.5%, soaking time 130 and 50 min and temperature 121 °C and 110 °C which yielded maximum delignification of 33.0% and 33.8% for DG and HNG respectively. Further ultrosono-assisted HCl pretreatment with a power supply of 100 W, temperature of 353 K, and duty cycle of 70% has resulted in significantly higher delignification of 80.4% and 82.1% for both DG and HNG respectively than that of acid pretreatment. Investigation using SEM, FTIR and autofloresence microscopy for both acid and ultrasono-assisted acid pretreatment lignocellulosic biomass revealed conformational changes of pretreated lignocellulosic biomass with decreased lignin content and increased exposure of cellulose, with greater effectiveness in case of ultrasono assisted acid pretreatment condition.

Effect of severity on dilute acid pretreatment of lignocellulosic biomass and the following hydrogen fermentation

This study aimed to investigate the relationship of the severity of dilute acid pretreatment and the following dark hydrogen fermentation performance. Empty palm fruit bunch, rice husk, and pine tree wood were hydrolyzed in 5% (v/v) H2SO4 at 10% (w/v) solid/liquid ratio and 121 °C for 30, 60, and 90 min, and then used as the substrate of batch hydrogen fermentation. The maximum sugar yield was achieved at pretreatment with 60 min reaction time; however, it did not guarantee the maximum H2 production. Hydrolyzate obtained from pretreatment where the combined severity factor was at or over 2.01 showed severe 5-hydroxymethylfurfural production and consequent decrease of H2 production rate. Peak H2 production rates of 2640, 3340, and 2565 mL H2 L−1 day−1 were achieved at the following severity factors: 1.95, 1.86, and 1.83, for empty palm fruit bunch, rice husk, and pine tree wood, respectively.

목질계 바이오매스로부터 생산된 바이오에탄올 투과증발 과정에서 발생한 투과증발 잔류물의 항산화 활성

In this study, we produced bioethanol from the original hydrolysate obtained during oxalic acid pretreatment of lignocellulosic biomass. The bioethanol was separated and concentrated by pervaporation and the residue after pervaporation was evaluated for its antioxidant activity. Xylose () was the major product in the original hydrolysate. The original hydrolysate contained acetic acid, furfural and total phenolic compounds (TPC) as fermentation inhibitors. Acetic acid was removed by electrodialysis (ED), and of bioethanol was produced from ED-treated hydrolysate. The TPC of ethyl acetate extracts from the residue obtained (OA-E) during pervaporation was 86.81 mg/100 g (extract). The values of DPPH and ABTS radical scavenging activities, and reducing power of OA-E were , , and , respectively. Sugar degradation products and the phenolic compounds in OA-E were determined by GC-MS.

Investigation of lignin deposition on cellulose during hydrothermal pretreatment, its effect on cellulose hydrolysis, and underlying mechanisms

In dilute acid pretreatment of lignocellulosic biomass, lignin has been shown to form droplets that deposit on the cellulose surface and retard enzymatic digestion of cellulose (Donohoe et al., 2008; Selig et al., 2007). However, studies of this nature are limited for hydrothermal pretreatment, with the result that the corresponding mechanisms that inhibit cellulosic enzymes are not well understood. In this study, scanning electron microscope (SEM) and wet chemical analysis of solids formed by hydrothermal pretreatment of a mixture of Avicel cellulose and poplar wood showed that lignin droplets from poplar wood relocated onto the Avicel surface. In addition, nuclear magnetic resonance (NMR) showed higher S/G ratios in deposited lignin than the initial lignin in poplar wood. Furthermore, the lignin droplets deposited on Avicel significantly impeded cellulose hydrolysis. A series of tests confirmed that blockage of the cellulose surface by lignin droplets was the main cause of cellulase inhibition. The results give new insights into the fate of lignin in hydrothermal pretreatment and its effects on enzymatic hydrolysis.

Oligomer Saccharide Reduction During Dilute Acid Pretreatment Co-Catalyzed with Lewis Acids on Corn Stover Biomass

The dilute sulfuric acid pretreatment of lignocellulosic biomass is a well understood process that significantly enhances the yield of glucose after enzymatic saccharification. The goal of this research was to perform a systematic study to evaluate the yield of fermentable sugars during dilute sulfuric acid pretreatment that is co-catalyzed with the transition metal Lewis acid salts: AlCl3, FeCl2, FeCl3, and La(OTf)3. All Lewis acids apart from FeCl2 reduced the presence of xylo-oligomers by a large margin when compared to the non-co-catalyzed control sample pretreatments. The presence of these xylo-oligomers acts as inhibitors during enzymatic saccaharification step. The Lewis acids AlCl3, FeCl3, and La(OTf)3 were also able to marginally increase the overall enzymatic digestibility specifically for corn stover pretreated at 160°C with 10 mM of Lewis acids. The hard Lewis acid such as AlCl3 increased the formation inhibitory products such as furfural and 5-hydroxymethylfurfural (HMF). There was good correlation between reduction of xylo-oligomers and increased concentration furfural with increase in Lewis acid hardness.

Comprehensive Study and Modeling of Acetic Acid Effect on Trichoderma reesei Growth

Abstract Acetic acid is one of the major potential inhibitors of cellular growth resulting from acid pretreatment of lignocellulosic biomass. To use lignocellulose hydrolysate in biorefineries it is necessary to assess their effect on the microorganisms likely to be used. An attractive option is to use a part of these hydrolysates for on-site cellulase production. Based on an industrial process that included a fast initial growth phase, the effect on Trichoderma reesei grown on glucose was assessed and modeled at different concentrations and pH. Acetic acid had a strong effect on T. reesei growth rate and yield, which correlated only with the concentration of the undissociated form in solution. The specific growth rate was accurately modeled by two different classic inhibition models as a function of pH and total acetic acid concentration. Co-consumption of glucose and acetic acid was observed, so that the culture medium was gradually detoxified by the cells. With or without glucose, acetic acid was miner...

Hydrothermal Carbons from Hemicellulose‐Derived Aqueous Hydrolysis Products as Electrode Materials for Supercapacitors

Acid pretreatment of lignocellulosic biomass, required for bioethanol production, generates large amounts of by-products, such as lignin and hydrolyzed hemicellulose fractions, which have found so far very limited applications. In this work, we demonstrate how the recovered hemicellulose hydrolysis products can be effectively utilized as a precursor for the synthesis of functional carbon materials through hydrothermal carbonization (HTC). The morphology and chemical structure of the synthesized HTC carbons are thoroughly characterized to highlight their similarities with glucose-derived HTC carbons. Furthermore, two routes for introducing porosity within the HTC carbon structure are presented: i) silica nanoparticle hard-templating, which is shown to be a viable method for the synthesis of carbonaceous hollow spheres; and ii) KOH chemical activation. The synthesized activated carbons (ACs) show an extremely high porosity (pore volume≈1.0 cm(3) g(-1)) mostly composed of micropores (90 % of total pore volume). Because of their favorable textural properties, the ACs are further tested as electrodes for supercapacitors, yielding very promising results (300 F g(-1) at 250 mA g(-1)) and confirming the high suitability of KOH-activated HTC carbons derived from spruce and corncob hydrolysis products as materials for electric double layer supercapacitors.

Steady State Analysis and Optimization of a Continuous Reactor for Acid Pretreatment of Lignocellulosic Biomass

The problem of modelling, operation and optimization of a dilute acid pretreatment reactor for lignocellulosic biomass is addressed. A continuous reactor model is developed based on rigorous mass and energy balances, including a complete kinetic mechanism. The process design and operation are studied through steady state and dynamic analysis, together with an optimization problem that maximizes the reaction rates of the sugar production and of lignin elimination. The sugarcane bagasse as lignocellulosic biomass is considered as case study. The results are presented in terms of yields of fermentable sugars and reaction times, defining operating ranges for an efficient continuous process. The methodology also gives guidelines to: improve experimental design, optimize the operating conditions and control the pretreatment process; reducing costs and effort of research and development.