A critical review on analysis in pretreatment of lignocelluloses: Degree of polymerization, adsorption/desorption, and accessibility

Lignocellulosic Biomass: Understanding Recalcitrance and Predicting Hydrolysis

Lignocellulosic biomass (LB) is an abundant and renewable resource from plants mainly composed of polysaccharides (cellulose and hemicelluloses) and an aromatic polymer (lignin). LB has a high potential as an alternative to fossil resources to produce second-generation biofuels and biosourced chemicals and materials without compromising global food security. One of the major limitations to LB valorisation is its recalcitrance to enzymatic hydrolysis caused by the heterogeneous multi-scale structure of plant cell walls. Factors affecting LB recalcitrance are strongly interconnected and difficult to dissociate. They can be divided into structural factors (cellulose specific surface area, cellulose crystallinity, degree of polymerization, pore size and volume) and chemical factors (composition and content in lignin, hemicelluloses, acetyl groups). Goal of this review is to propose an up-to-date survey of the relative impact of chemical and structural factors on biomass recalcitrance and of the most advanced techniques to evaluate these factors. Also, recent spectral and water-related measurements accurately predicting hydrolysis are presented. Overall, combination of relevant factors and specific measurements gathering simultaneously structural and chemical information should help to develop robust and efficient LB conversion processes into bioproducts.

A simplified model to simulate bioaugmented anaerobic digestion of lignocellulosic biomass: Biogas production efficiency related to microbiological data

Mathematical model applications for the bioaugmented anaerobic digestion (BAD) process seem to be lacking in the scientific literature, even more so when related to microbiological data. The present study suggests a simplified mathematical model to investigate and simulate the process kinetics of bioaugmented anaerobic digestion (BAD) aimed at improving biogas production from wheat straw (WS). Bioaugmented conditions were obtained through a mixed inoculum of anaerobic ruminal fungi (ARF) and hydrogen-producing fermenting bacteria (F210) added to a methanogenic inoculum. The investigation focused on two process configurations characterized by a mono (I-BAD) and two-stage (II-BAD) process and a conventional anaerobic digestion (AD) control test. Each configuration was used on two operating scales (i.e., 120 ml and 12,000 ml reactor volume) to provide different data sets for the calibration and validation of the mathematical model proposed. The model calibration step was used to determine the optimal values of selected parameters displaying higher significance for experimental result predictability. The model calibration results highlighted a similar behavior for both BAD tests, which was further strengthened by a statistical analysis supporting the observed correlation regardless of the BAD configuration involved. The BAD configuration always enhanced the CH₄ production (>70%) with a faster kinetic in the II-BAD test. The microbiological results support the superior performance of the II-BAD test, displaying higher Archaea fractions (up to 14.5% on day 23) with values more than double compared to I-BAD and triple compared to the AD test. Furthermore, the presence of Methanosarcina inside the Archaea guild (6.4% and 4.5% at days 11 and 61, respectively) ensures a greater diversification of the metabolic pathways and supports the strength of the process performance. Cell density values are strongly in line with these results.

Production and purification of laccase by Bacillus sp. using millet husks and its pesticide degradation application

Lignocellulosic agricultural bi-products, pearl millet (PM) and finger millet (FM) husks, were used for the production of laccase using Bacillus sp. PS under solid-state fermentation (SSF). Abiotic variables such as substrate (PM, FM) concentration (1-5%), incubation time (24-96 h) and pH (5-10) were optimized using Response surface methodology (RSM) to maximize the laccase production. The predicted model showed maximum laccase activity of 402 U/mL appearing after 96 h of incubation with PM 2.0 g/L and FM 1.5 g/L at pH 7.0. Single protein band on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) confirmed homogeneity of the laccase with a molecular weight of 63-75 kDa. The partially purified laccase effectively degraded the pesticides (Tricel, 71.8 ± 3.5 and Phoskill 77.3 ± 3.4%) within 5 days of incubation (40 °C) in pH 7.0. The pesticide degradation was further confirmed by high-performance liquid chromatography (HPLC) and the chromatograms showed the single dominant peaks at retention time 2.482 (tricel) and 2.608 (phoskill) min, respectively. Pesticide-degrading laccase was produced by Bacillus sp. PS under SSF reveals the utilization of low-cost bi-substrates for enhanced laccase production.

Sugar production from bioenergy sorghum by using pilot scale continuous hydrothermal pretreatment combined with disk refining

Chemical-free pretreatments are attracting increased interest because they generate less inhibitor in hydrolysates. In this study, pilot-scaled continuous hydrothermal (PCH) pretreatment followed by disk refining was evaluated and compared to laboratory-scale batch hot water (LHW) pretreatment. Bioenergy sorghum bagasse (BSB) was pretreated at 160-190 °C for 10 min with and without subsequent disk milling. Hydrothermal pretreatment and disk milling synergistically improved glucose and xylose release by 10-20% compared to hydrothermal pretreatment alone. Maximum yields of glucose and xylose of 82.55% and 70.78%, respectively were achieved, when BSB was pretreated at 190 °C and 180 °C followed by disk milling. LHW pretreated BSB had 5-15% higher sugar yields compared to PCH for all pretreatment conditions. The surface area improvement was also performed. PCH pretreatment combined with disk milling increased BSB surface area by 31.80-106.93%, which was greater than observed using LHW pretreatment.

Insight into Pretreatment Methods of Lignocellulosic Biomass to Increase Biogas Yield: Current State, Challenges, and Opportunities

Lignocellulosic biomass is recalcitrant due to its heterogeneous structure, which is one of the major limitations for its use as a feedstock for methane production. Although different pretreatment methods are being used, intermediaries formed are known to show adverse effect on microorganisms involved in methane formation. This review, apart from highlighting the efficiency and limitations of the different pretreatment methods from engineering, chemical, and biochemical point of views, will discuss the strategies to increase the carbon recovery in the form of methane by way of amending pretreatments to lower inhibitory effects on microbial groups and by optimizing process conditions.

Biomethane Production From Lignocellulose: Biomass Recalcitrance and Its Impacts on Anaerobic Digestion

Anaerobic digestion using lignocellulosic material as the substrate is a cost-effective strategy for biomethane production, which provides great potential to convert biomass into renewable energy. However, the recalcitrance of native lignocellulosic biomass makes it resistant to microbial hydrolysis, which reduces the bioconversion efficiency of organic matter into biogas. Therefore, it is necessary to critically investigate the correlation between lignocellulose characteristics and bioconversion efficiency. Accordingly, this review comprehensively summarizes the anaerobic digestion process and rate-limiting step, structural and compositional properties of lignocellulosic biomass, recalcitrance and inhibitors of lignocellulose and their major effects on anaerobic digestion for biomethane production. Moreover, various type of pretreatment strategies applied to lignocellulosic biomass was discussed in detail, which would contribution to cell wall degradation and improvement of biomethane yields. In the view of current knowledge, high energy input and cost requirements are the main limitations of these pretreatment methods. In addition to optimization of fermentation process, further studies should focus much more on key structural influence factors of biomass recalcitrance and anaerobic digestion efficiency, which will contribute to improvement of biomethane production from lignocellulose.

Substrate-Related Factors Affecting Cellulosome-Induced Hydrolysis for Lignocellulose Valorization

Cellulosomes are an extracellular supramolecular multienzyme complex that can efficiently degrade cellulose and hemicelluloses in plant cell walls. The structural and unique subunit arrangement of cellulosomes can promote its adhesion to the insoluble substrates, thus providing individual microbial cells with a direct competence in the utilization of cellulosic biomass. Significant progress has been achieved in revealing the structures and functions of cellulosomes, but a knowledge gap still exists in understanding the interaction between cellulosome and lignocellulosic substrate for those derived from biorefinery pretreatment of agricultural crops. The cellulosomic saccharification of lignocellulose is affected by various substrate-related physical and chemical factors, including native (untreated) wood lignin content, the extent of lignin and xylan removal by pretreatment, lignin structure, substrate size, and of course substrate pore surface area or substrate accessibility to cellulose. Herein, we summarize the cellulosome structure, substrate-related factors, and regulatory mechanisms in the host cells. We discuss the latest advances in specific strategies of cellulosome-induced hydrolysis, which can function in the reaction kinetics and the overall progress of biorefineries based on lignocellulosic feedstocks.

Fuzzy-Enhanced Modeling of Lignocellulosic Biomass Enzymatic Saccharification

The enzymatic hydrolysis of lignocellulosic biomass incorporates many physico-chemical phenomena, in a heterogeneous and complex media. In order to make the modeling task feasible, many simplifications must be assumed. Hence, different simplified models, such as Michaelis-Menten and Langmuir-based ones, have been used to describe batch processes. However, these simple models have difficulties in predicting fed-batch operations with different feeding policies. To overcome this problem and avoid an increase in the complexity of the model by incorporating other phenomenological terms, a Takagi-Sugeno Fuzzy approach has been proposed, which manages a consortium of different simple models for this process. Pretreated sugar cane bagasse was used as biomass in this case study. The fuzzy rule combines two Michaelis-Menten-based models, each responsible for describing the reaction path for a distinct range of solids concentrations in the reactor. The fuzzy model improved fitting and increased prediction in a validation data set.

Fractionation of Lignocellulosic Biomass by Selective Precipitation from Ionic Liquid Dissolution

We propose the treatment of barley straw with 1-ethyl-3-methylimidazolium acetate [EMIMAcO] ionic liquids (ILs) and subsequent precipitation with antisolvent mixtures, thus allowing the separation of the sugar-rich fractions (cellulose and hemicellulose) from the lignin fraction. For this purpose, different concentration ranges of acetone:water antisolvent mixtures were studied. In all cases, a high recovery percentage and a high and effective separation of fractions was achieved for 1:1 acetone:water. The fractionated lignocellulosic compounds were studied by using infrared spectroscopy, scanning electron microscopy and 1H nuclear magnetic resonance characterization techniques. This method allows the possibility of reusing IL, confirming the versatility of the established method. The fraction rich in cellulose and hemicellulose was subjected to acid hydrolysis (0.2 mol/L H2SO4) for 5 h at 140 °C, obtaining a yield of total reducing sugars of approximately 80%, much higher than those obtained in non-pretreated samples.

Sugarcane Bagasse Hydrolysis Enhancement by Microwave-Assisted Sulfolane Pretreatment

Sugarcane bagasse is the major by-product of the sugarcane industry and, due to its abundant availability, it has been extensively studied for lignocellulosic bioconversion in the production of bioethanol and other value-added commercial products. In the study presented herein, a combined pretreatment using sulfolane, TiO2 and alkali microwave irradiation (MW-A) was assessed for the dissolution of lignin prior to enzymatic saccharification of holocellulose. Total reducing sugars (TRS) and saccharinic acid yields were investigated. The increase in NaOH concentration up to 5% and in temperature from 120 °C to 140 °C were found to have a positive influence on both yields. While increasing the reaction time from 5 to 60 min only led to an increase in TRS yield <2%, a reaction time of 30 min almost doubled the saccharinic acids production. TRS yields and saccharinic acid production were approximately 5% and 33% higher when the sulfolane-TiO2 reaction medium was used, as compared to MW-A in water, reaching up to 64.8% and 15.24 g/L of saccharinic acids, respectively. The proposed MW-A pretreatment may hold promise for industrial applications, given the good TRS yields obtained, and the associated enzyme and time/energy savings. The use of sulfolane-TiO2 reaction medium is encouraged if saccharinic acids are to be recovered too.

Bioethanol production from bamboo with alkali-catalyzed liquid hot water pretreatment

Altering recalcitrant structures of bamboo is essential to obtain high yield of bioethanol via bioconversion process. With the goal of improving cell wall digestibility, alkaline liquid hot water was used to pretreat N. affinis. The effects of temperature and alkali dosage on structural alterations were determined by chemical composition, Brunauer Emmett Teller (BET) and gel permeation chromatography (GPC). The relationship between these changes and substrate digestibility was addressed by separate enzymatic hydrolysis and fermentation (SHF). The results indicated that pretreatments partly removed and degraded hemicelluloses and lignin, reducing yields of substrates and molecular weights of carbohydrates. With the change of cell wall structure, specific surface area of materials increased after LHW pretreatment but decreased with further removal of lignin and hemicellulosic fractions. Maximum bioconversion was obtained by pretreatment with 0.5% NaOH aqueous at 170 °C and SHF, yielding 4.8 g/L ethanol.

Alkali/urea pretreatment of rice straw at low temperature for enhanced biological hydrogen production

A pretreatment process using alkali/urea solution at low temperature was proposed for enhanced cellulosic biohydrogen production. Different alkaline solutions with both presence and absence of urea were studied. It can be found NaOH/Urea pretreatment exhibited excellent pretreatment performance at temperature from -8 °C to -20 °C. Microscopic structure observation combined FTIR analysis further demonstrated that NaOH/Urea pretreatment at low temperature could effectively disrupt the structure of rice straw and made more cellulose and hemicellulose available. The pretreated materials were then subjected for biohydrogen production by Thermoanaerobacterium thermosaccharolyticum M18. The maximum hydrogen production and energy conversion efficiency of 22.08 mmol/L and 9.76% were obtained from NaOH/Urea pretreated rice straw at low temperature. The results were 161.92% and 56.91% higher than the counterpart without pretreatment, respectively. This study provides a new direction to pretreat lignocellulose efficiently for enhanced biohydrogen production at cold climate region.

Effect of iron salt type and dosing mode on Fenton-based pretreatment of rice straw for enzymatic hydrolysis

Fenton-based processes with four different iron salts in two different dosing modes were used to pretreat rice straw (RS) samples to increase their enzymatic digestibility. The composition analysis shows that the RS sample pretreated by the dosing mode of iron salt adding into H₂O₂ has a much lower hemicellulose content than that pretreated by the dosing mode of H₂O₂ adding into iron salt, and the RS sample pretreated by the chloride salt-based Fenton process has a much lower lignin content and a slightly lower hemicellulose content than that pretreated by the sulphate salt-based Fenton process. The higher concentration of reducing sugar observed on the RS sample with lower lignin and hemicellulose contents justifies that the Fenton-based process could enhance the enzymic hydrolysis of RS by removing hemicellulose and lignin and increasing its accessibility to cellulase. FeCl₃·6H₂O adding into H₂O₂ is the most efficient Fenton-based process for RS pretreatment.

Prospecting of soybean hulls as an inducer carbon source for the cellulase production

Cellulases constitute an enzymatic complex involved in the cellulose hydrolysis β-1, 4-glycosidic linkages to release of glucose. Therefore, its application to degrade agro-industrial residues becomes relevant, since glucose is a product of industrial interest, aiming at its conversion into biocommodity production (e.g., enzymes, bioethanol and other value-added biochemicals). Thus, in natura Soybean hulls as well as fractions obtained from its alkaline, autohydrolysis and organosolv pretreatments were used as carbon sources in submerged fermentation processes to evaluate the cellulase-inducing capacity using a Penicillium sp. strain. Results showed an inductive effect on the production of 0.130 and 0.066 U/mL for CMCase and FPase, respectively, using 1% of the in natura residue. Regarding the fraction obtained from soybean hulls pretreated by autohydrolysis and organosolv, avicelase and β-Glucosidase displayed a production of 0.200 and 0.550 U/mL, respectively. Therefore, the use of pretreated Soybean hull revealed its potential as an alternative carbon source for the cellulase production, which may contribute significantly to biotechnological purposes by adding value to an agro-industrial residue.

Eco-friendly process combining acid-catalyst and thermomechanical pretreatment for improving enzymatic hydrolysis of hemp hurds

The aim of this study was to investigate a pretreatment by combined H₂SO₄ acid-catalyst and thermomechanical process to improve hemicelluloses solubilization of hemp hurds and subsequently enzymatic hydrolysis extent of potentially fermentable sugars. It was found that the sugars released were gradually increased with treatment severity. Soluble sugars generated before enzymatic hydrolysis (R₁) increased up to 2.23 g/L indicating that autohydrolysis reaction occurred during pretreatment. Consequently, the solubilization of hemicelluloses was correlated with combined severity factor (CS). As a result, increase of overall reducing sugars (ORS) from 23.4% (untreated) to 81.4% was observed at optimized conditions of steaming temperature of 165 °C for 30 min and acid loading of 62.9 g/kg DM (dry material) corresponding to CS = 1.2, with limited production of identified by-products: 0.035 g/L and 0.46 g/L (per 100 g DM) for furfural and HMF, respectively. Structural and physicochemical modifications of biomass were observed by FTIR, A_BET and SEM.

Determination of optimal biomass pretreatment strategies for biofuel production: investigation of relationships between surface-exposed polysaccharides and their enzymatic conversion using carbohydrate-binding modules

BACKGROUND

Pretreatment of lignocellulosic biomass (LCB) is a key step for its efficient bioconversion into ethanol. Determining the best pretreatment and its parameters requires monitoring its impacts on the biomass material. Here, we used fluorescent protein-tagged carbohydrate-binding modules method (FTCM)-depletion assay to study the relationship between surface-exposed polysaccharides and enzymatic hydrolysis of LCB.

RESULTS

Our results indicated that alkali extrusion pretreatment led to the highest hydrolysis rates for alfalfa stover, cattail stems and flax shives, despite its lower lignin removal efficiency compared to alkali pretreatment. Corn crop residues were more sensitive to alkali pretreatments, leading to higher hydrolysis rates. A clear relationship was consistently observed between total surface-exposed cellulose detected by the FTCM-depletion assay and biomass enzymatic hydrolysis. Comparison of bioconversion yield and total composition analysis (by NREL/TP-510-42618) of LCB prior to or after pretreatments did not show any close relationship. Lignin removal efficiency and total cellulose content (by NREL/TP-510-42618) led to an unreliable prediction of enzymatic polysaccharide hydrolysis.

CONCLUSIONS

Fluorescent protein-tagged carbohydrate-binding modules method (FTCM)-depletion assay provided direct evidence that cellulose exposure is the key determinant of hydrolysis yield. The clear and robust relationships that were observed between the cellulose accessibility by FTCM probes and enzymatic hydrolysis rates change could be evolved into a powerful prediction tool that might help develop optimal biomass pretreatment strategies for biofuel production.

Formulation of an optimized synergistic enzyme cocktail, HoloMix, for effective degradation of various pre-treated hardwoods

In this study, two selected hardwoods were subjected to sodium chlorite delignification and steam explosion, and the impact of pre-treatments on synergistic enzymatic saccharification evaluated. A cellulolytic core-set, CelMix, and a xylanolytic core-set, XynMix, optimised for glucose and xylose release, respectively, were used to formulate HoloMix cocktail for optimal saccharification of various pre-treated hardwoods. For delignified biomass, the optimized HoloMix consisted of 75%:25% protein dosage, CelMix: XynMix, while for untreated and steam exploded biomass the HoloMix consisted of 93.75%:6.25% protein dosage. Saccharification by HoloMix (27.5mgprotein/gbiomass) for 24h achieved 70-100% sugar yields. Pre-treatment of the hardwoods (especially those with a higher proportion of lignin) with a laccase, improved saccharification by HoloMix. This study provided insights into enzymatic hydrolysis of various pre-treated hardwood substrates and showed the same lignocellulolytic cocktail comparable to/if not better than commercial enzyme preparations can be used to efficiently hydrolyse different hardwood species.

Additives enhancing enzymatic hydrolysis of lignocellulosic biomass

Linked to the development of cellulolytic enzyme cocktails from Myceliophthora thermophila, we studied the effect of different additives on the enzymatic hydrolysis yield. The hydrolysis of pretreated corn stover (PCS), sugar cane straw (PSCS) and microcrystalline cellulose (Avicel) was performed under industrial conditions using high solid loadings, limited mixing, and low enzyme dosages. The addition of polyethylene glycol (PEG4000) allowed to increase the glucose yields by 10%, 7.5%, and 32%, respectively in the three materials. PEG4000 did not have significant effect on the stability of the main individual enzymes but increased beta-glucosidase and endoglucanase activity by 20% and 60% respectively. Moreover, the presence of PEG4000 accelerated cellulase-catalyzed hydrolysis reducing up to 25% the liquefaction time. However, a preliminary economical assessment concludes that even with these improvements, a lower contribution of PEG4000 to the 2G bioethanol production costs would be needed to reach commercial feasibility.

Ultrasound-assisted alkaline pretreatment for enhancing the enzymatic hydrolysis of rice straw by using the heat energy dissipated from ultrasonication

Rice straw samples were exposed to ultrasound-assisted alkaline (NaOH) pretreatment by using the heat energy dissipated from ultrasonication to increase their enzymatic digestibility for saccharification. The characterization shows that the pretreatment could selectively remove lignin and hemicellulose without degrading cellulose, and increase porosity and surface area of rice straw. The porosity, surface area and cellulose content of rice straw increased with the increasing concentration of NaOH used. The rice straw sample pretreated by using the heat energy dissipated from ultrasonication has a higher surface area and a lower crystallinity index value than that pretreated by using the external source of heating, and the amount of reducing sugar released from the former sample at 48h of enzymatic saccharification, which is about 3.5 times as large as that from the untreated rice straw sample (2.91vs. 0.85gL^-1), is slightly larger than that from the latter sample (2.91vs. 2.73gL^-1). The ultrasound-assisted alkaline pretreatment by using the heat energy dissipated from ultrasonication was proved to be a reliable and effective method for rice straw pretreatment.

Dilute alkali pretreatment of softwood pine: A biorefinery approach

Dilute alkali pretreatment was performed on softwood pine to maximize ethanol and biogas production via a biorefinery approach. Alkali pretreatments were performed with 0-2% w/v NaOH at 100-180°C for 1-5h. The liquid fraction of the pretreated substrates was subjected to anaerobic digestion. The solid fraction of the pretreatment was used for separate enzymatic hydrolysis and fermentation. High ethanol yields of 76.9‒78.0% were achieved by pretreatment with 2% (w/v) NaOH at 180°C. The highest biogas yield of 244mL/g volatile solid (at 25°C, 1bar) was achieved by the pretreatment with 1% (w/v) NaOH at 180°C. The highest gasoline equivalent (sum of ethanol and methane) of 197L per ton of pinewood and the lowest ethanol manufacturing cost of 0.75€/L was obtained after pretreatment with 1% NaOH at 180°C for 5h. The manufacturing cost of ethanol from untreated wood was 4.12€/L.

Pretreatment of rice straw by ultrasound-assisted Fenton process

Fenton's reagent, ultrasound, and the combination of Fenton's reagent and ultrasound were used to pretreat rice straw (RS) to increase its enzymatic digestibility for saccharification. The characterization shows that compared with ultrasound, Fenton's reagent pretreatment was more efficient in increasing the specific surface area and decreasing the degree of polymerization (DP) of RS. The enzymatic hydrolysis results showed that the RS pretreated by ultrasound-assisted Fenton's reagent (U/F-RS), which exhibited the largest specific surface area and the lowest DP value, had the highest enzymatic activity, and the amount of reducing sugar released from U/F-RS at 48h of enzymatic saccharification is about 4 times as large as that from raw RS and 1.5 times as large as that from Fenton's reagent pretreated RS. The ultrasound-assisted Fenton process provides a reliable and effective method for RS pretreatment.

Unconventional Pretreatment of Lignocellulose with Low-Temperature Plasma

Lignocellulose represents a potential supply of sustainable feedstock for the production of biofuels and chemicals. There is, however, an important cost and efficiency challenge associated with the conversion of such lignocellulosics. Because its structure is complex and not prone to undergo chemical reactions very easily, chemical and mechanical pretreatments are usually necessary to be able to refine them into the compositional building blocks (carbohydrates and lignin) from which value-added platform molecules, such as glucose, ethylene glycol, 5-hydroxymethylfurfural, and levulinic acid, and biofuels, such as bioderived naphtha, kerosene, and diesel fractions, will be produced. Conventional (wet) methods are usually polluting, aggressive, and highly energy consuming, so any alternative activation procedure of the lignocellulose is highly recommended and anticipated in recent and future biomass research. Lignocellulosic plasma activation has emerged as an interesting (dry) treatment technique. In the long run, in particular, in times of fairly accessible renewable electricity, plasma may be considered as an alternative to conventional pretreatment methods, but current knowledge is too little and examples too few to guarantee that statement. This review therefore highlights recent knowledge, advancements, and shortcomings in the field of plasma treatment of cellulose and lignocellulose with regard to the (structural and chemical) effects and impact on the future of pretreatment methods.

Abnormal adsorption and desorption behavior of pharmaceutical drugs on polystyrene microspheres

We report an abnormal adsorption and desorption behavior where a stronger adsorption interaction between polystyrene particles and pharmaceutical drugs results in preferable desorption behavior.

Fenton pre-treatment of rice straw with citric acid as an iron chelate reagent for enhancing saccharification

Rice straw was pre-treated by Fenton action with citric acid for chelation; the pre-treated rice straw was saccharified byRuminiclostridium thermocellumM3.

Chemical and structural analysis of alkali pretreated pinewood for efficient ethanol production

Improvement of enzymatic hydrolysis and ethanol production from softwood pine was conducted by pretreatment with 8% (w/v) NaOH at different temperatures of 0, 25, and 80 °C for 2 h.