Search

Pretreatment is a necessary process in biorefineries to overcome recalcitrance of biomass and enhance its conversion efficiency for further transformation. NaOH activation of Na2S2O8, which merges alkaline pretreatment and advanced oxidation processes (AOPs) into one process, was performed at room temperature (25 °C) within a short duration (60 min). High concentration of NaOH plays a critically important role in NaOH–Na2S2O8 pretreatment, which not only selectively removed hemicellulose in the lignocellulosic feedstock, but also activated Na2S2O8 to produce strong oxidative radicals, leading to disruption of lignin matrix. The surface area and porosity for the pretreated feedstock were significantly increased compared with those of the pristine counterpart. After pretreatment by 5.12 M NaOH and 0.85 M Na2S2O8, the maximum glucose yield of the feedstock was increased by 47.4% compared with that of pristine counterpart (60.3% vs. 40.9%). This study provides an effective and easily-realizable pretreatment method for the utilization of lignocellulosic biomass. [ABSTRACT FROM AUTHOR]

Copyright of China Brewing is the property of China Brewing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

[Display omitted] • Alkaline pretreatment had a slight effect on microalgal biomass harvesting. • Solubilisation of microalgae was studied using three enzymatic cocktails. • Lower enzymatic doses attained less solubilisation but 9–27% higher methane yields. • Secondary sludge was co-digested with non- and enzymatically pretreated microalgae. • Enzymatic pretreatment did not enhance biogas production in algae-WAS co-digestion. Integration of microalgae-based systems with conventional wastewater treatment plants provides an effective alternative to waste stream management. In this work, alkaline and enzymatic pretreatments of a microalgal culture mainly constituted by Chlorella sp. and Scenedesmus sp. and cultivated in wastewater from an industrial winery wastewater treatment plant were assessed. Microalgal enzymatic pretreatments were expected to overcome algal recalcitrancy before anaerobic digestion. pH-induced flocculation at pH 10 and 11 did not enhance microalgal harvesting and solubilisation, achieving a performance similar to that of natural sedimentation. Enzymatic hydrolysis of algal biomass was carried out using three commercial enzymatic cocktails (A, B and C) at two enzymatic doses (1% and 2% (v/v)) over 3 h of exposure time at 37 °C. Since pretreatments at a 1% dose for 0.5 h and 2% dose for 2 h achieved higher solubilisation, they were selected to evaluate the influence of the pretreatment on microalgal anaerobic digestibility. Biochemical methane potential tests showed that the pretreatments increased the methane production of the raw algal biomass 3.6- to 5.3-fold. The methane yield was 9–27% higher at the lower enzyme dose. Hence, microalgae pretreated with enzymes B and C at a 1% dose were co-digested with waste activated sludge (WAS). Even when the enzyme increased the methane yield of the inoculum and the WAS, the methane yield of the raw microalgae and WAS mixture was not significantly different from that obtained when algae were enzymatically pretreated. Nonetheless, co-digestion may achieve the goals of a waste recycled bio-circular economy. [ABSTRACT FROM AUTHOR]

In the present study, sugarcane bagasse (SB) was subjected to different pretreatments. The pretreated SB was characterized chemically and structurally and was enzymatically hydrolyzed using a commercial enzyme preparation. Pretreatment with sulfite-NaOH was the most efficient for removing lignin while keeping cellulose intact. In addition, sulfite-NaOH pretreatment presented the best response to the enzymatic hydrolysis of cellulose and xylan, reaching conversions of 90%. The increase in consistency (≥10%) in the enzymatic hydrolysis of SB pretreated with sulfite-NaOH showed a loss of cellulose and xylan conversions efficiencies of 28 and 37%, respectively. However, enzymatic hydrolysis with a consistency of 20% resulted in a maximum rate of glucose and xylose formation of 8.5 and 3.0 g L−1 h−1, respectively, and an enzymatic hydrolysate containing 80 and 33 g L−1 of glucose and xylose, respectively. The enzymatic hydrolysis assay in a bioreactor with 20% consistency promoted faster liquefaction of SB, resulting in a higher maximum rate of glucose production (10.6 g L−1 h−1). The increase in the concentration and rate of formation of fermentable sugars in the enzymatic hydrolysate can partially avoid steps of concentration of the hydrolysate, resulting in less energy consumption and greater productivity of the bioproducts obtained from the hydrolysate, such as cellulosic ethanol (2G ethanol). Image 1 • Pretreatment of sugarcane bagasse with sulfite-NaOH efficiently removed lignin. • Pretreatment with sulfite-NaOH had the strongest effect on the enzymatic hydrolysis. • Enzymatic hydrolysis under high consistency resulted in hydrolysate rich in sugars. • Enzymatic hydrolysis performed in bioreactor show maximum rate of glucose increased. [ABSTRACT FROM AUTHOR]

Solid waste from sisal fiber is a great candidate for biorefinery feedstock and material for composite production. However, sisal solid waste needs to be pre-treated before being used for such application. One of pretreatment method is chemical pretreatment process using alkaline solution. Alkaline pretreatment can improve the digestibility and physicochemical properties of this lignocellulosic material. The aim of this study was to characterize the in natura and alkali pretreated sisal solid waste in order to evaluate their potential as biorefinery feedstock and material for composite production. The chemical characterization showed that the pretreatment resulted in an increase in cellulose content, which is in agreement with the results of infrared spectra. The DRX pattern and thermal characterization showed a crystallinity degree increase and thermal stability improving, respectively, indicating a partial removal of the amorphous fraction of the lignocellulosic material. The SEM analysis showed that the pretreatment increased the sisal solid waste superficial area, due to extractives removing. These results contributed to elucidate the potential uses of the lignocellulosic material from sisal and how the dilute alkaline pretreatment affected its composition and physicochemical properties. [ABSTRACT FROM AUTHOR]

The elimination of diclofenac traces from aqueous environments is important. In this research, the effect of alkaline (NaOH) pretreatment on clinoptilolite before its modification with a surfactant (HDTMA) for diclofenac adsorption under the speculation of the sole presence of diclofenac in the aqueous solution is investigated. The results are compared through isotherm, kinetic, and thermodynamic studies and supplemented by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Brunauer--Emmett--Teller (BET), and the zeta potential analyses. The contact time was investigated in a 0-180-min range. The pH effect was studied in a range of 5-10 because of diclofenac dissociation below pH¼ 5. The effect of the temperature on diclofenac adsorption was also considered by establishing the experiments at 25, 35, and 45 °C. For HDTMA-modified clinoptilolite, Temkin, and for NaOH-HDTMA-modified clinoptilolite, Dubinin--Radushkevich, and Freundlich isotherm models and in both cases, the pseudo-second-order kinetic model fitted the experimental data best. All the enthalpy and the entropy changes were negative, suggesting exothermic adsorption with a decrease in the degree of freedom of diclofenac anions after the adsorption. Furthermore, diclofenac physisorption was confirmed through isotherm and kinetic studies. [ABSTRACT FROM AUTHOR]

The present study, sugarcane straw residue (SCS) was submitted to a combination of mild alkaline pretreatment and ozone cycles in a rotary reactor aiming to obtain fermentable sugars. The SCS exposed to short ozone cycles and short reaction times proved to be as efficient as long ozone exposure times usually employed, with no significant variation on the concentration of the fermentable sugars. Also, studies carried out on the ozone concentration, ozone exposure time, reaction time and biomass amount on the ozonolysis process were conducted. The washing processes after alkaline pretreatment and ozonolysis were also studied. During the alkaline pretreatment, approximately 73% of total phenolic compounds (TPC) was generated. After the first wash 79% of the TPC was washed away and 95% was removed after the second wash. The TPC content in wash solution obtained after ozonolysis is about 2.3% of the TPC generated with the alkaline pretreatment. For the enzymatic hydrolysate 0.20 g L−1 of TPC was obtained, a low value compared to similar studies. The inhibitor detected in the highest concentration was acetic acid for all solutions, except for ozonolysis where fumaric acid predominated. Hydroxymethylfurfural (HMF) and furfural were detected in amounts of less than 10 mg L−1. Image 1 • O 3 short-pulses in rotary reactor were more efficient than continuous flow. • Short O 3 cycle was as efficient as longer ones previously described in literature. • Ozone concentration is not directly related with sugars release. • Rotary reactor utilization enhanced the amount of fermentable sugars. • Ozonolysis and alkaline treatments did not generate significative amounts of TPC. [ABSTRACT FROM AUTHOR]

Low biodegradability caused by polymeric structure is the main barrier in the use of lignocellulosic materials in biofuels production by using biological methods. Pretreatment of the biomass is the way to improve the suitability of hardly biodegradable biomass for biogas or bioethanol production. Evaluation of the influence of thermal and thermochemical alkaline pretreatment on the efficiency of hydrolysis of hay (mixture of various grass species) was the aim of the study. The batch scale experiment was carried out with the use of NaOH and distilled water as solvents, and the changes in pretreatment time (2, 4 and 8 hours) and temperature (22 and 80°C) were also considered. The efficiency of biomass solubilisation was assessed based on the results obtained from the measurements of chemical oxygen demand (COD) and volatile fatty acids (VFA) concentration in the hydrolysates. The solubility of the biomass, expressed as a percentage of soluble COD in total COD, was calculated. The experiment showed that the highest solubilisation of hay biomass was observed at 80°C under alkaline conditions. In this case, the solubility of the COD was 3-times higher, and the VFA concentration in hydrolysates was 4-times higher in comparison to the distilled water-based test at 22°C. It was noted that time of the process significantly influenced the efficiency of biomass solubilisation only during the experiment carried out at 22°C. Extension of hydrolysis time from 2 to 8 hours increased the value of soluble COD of 70% and 55% for water and alkaline solvent, respectively. The process conducted at 80°C was not time-dependent over the considered period. [ABSTRACT FROM AUTHOR]

This study investigates enhancing the biogas production of sunnhemp by pretreatment, before the anaerobic digestion and co-digestion processes, to address the complex and recalcitrant structure of the plant. Fresh sunnhemp harvested at a cutting interval of 50 days is used in the study. Five systems (each with a 5 litre useable volume) are operated semi-continuously with five different ratios of the feedstock by feeding separate feedstocks every five days with a hydraulic retention time (HRT) of 40 days. The system operates at room temperature (30 °C). The study uses sunnhemp as 20% of the feedstock and also considers sunnhemp mixed with cow manure at different ratios, with the weighed sunnhemp being pretreated with dilute sodium hydroxide. Pretreatment of sunnhemp before digestion produces a methane (CH 4) yield 89% greater than that of the untreated sunnhemp. It requires 3.597 kg of dry sunnhemp to produce 1 m3 of CH 4 and the annual CH 4 yield per hectare is 19,015 m3. In the pretreatment of sunnhemp before co-digestion, the increased CH 4 yield depends on the amount of pretreated sunnhemp in the feedstocks. However, the %CH 4 , the CH 4 production level and the system stability depend on the optimal ratio of the sunnhemp to cow manure. The initially prepared sunnhemp to cow manure ratio is recommended at 10 g:10 g in 80 mL of water. At this ratio, the %CH 4 and the CH 4 yield are 53.84% and 313 kg chemical oxygen demand (COD) removed, respectively, and the COD removal efficiency is 56.4%. Sunnhemp has high potential and it is worth pretreating before producing biogas. Using sunnhemp to produce biogas is recommended to decrease greenhouse gas emissions and mitigate global warming. • A promising way to increase biogas from sunnhemp is to pretreat it with NaOH. • The CH 4 yield obtained is 89% greater than from the untreated sunnhemp. • To produce 1 m3 of CH 4 requires 3.597 kg sunnhemp when pretreated. • The appropriate initially prepared sunnhemp:cow manure is 10g:10g in 80 mL of water. • Pretreated sunnhemp has high potential for biogas production. [ABSTRACT FROM AUTHOR]

Marigold (Calendula officinalis) market is focused on the extraction of compounds from the flower for homeopathic applications. However, most of the body plant is left as waste for final disposition. This work aims to show an integral valorization of leaves and stem of marigold to produce biogas and phenolic compounds such as vanillin and vanillic acid in a biorefinery scheme. An alkaline pretreatment was carried out to obtain black liquor and to favor the digestibility of the solid residue. The black liquor was oxidized in a high-pressure reactor, reaching experimental yields of 5.09% and 1.16% (based on lignin) for vanillin and vanillic acid, respectively. The remaining solid fraction was fermented through anaerobic digestion, achieving biogas productivity of 1621.3 mL/g of volatile solids. Afterward, these experimental results were used as input parameters to simulate and analyze a potential biorefinery. It was demonstrated that the anaerobic digestion stage affects up to 59% of the capital costs and that the positive economic gains were achieved at flow rates greater than 6.64 ton/h. [ABSTRACT FROM AUTHOR]

Bamboo is a promising biomass resource. However, the complex multilayered structure and chemical composition of bamboo cell walls create a unique anti-depolymerization barrier, which increases the difficulty of separation and utilization of bamboo. In this study, the relationship between the connections of lignin-carbohydrate complexes (LCCs) within bamboo cell walls and their multilayered structural compositions was investigated. The chemical composition, structural properties, dissolution processes, and migration mechanisms of LCCs were analyzed. Alkali-stabilized LCC bonds were found to be predominantly characterized by phenyl glycoside (PhGlc) bonds along with numerous p -coumaric acid (PCA) linkage structures. As demonstrated by the NMR and CLSM results, the dissolution of the LCC during the alkaline pretreatment process was observed to migrate from the inner secondary wall (S-layer) of the bamboo fiber cell walls to the cell corner middle lamella (CCML) and compound middle lamella (CML), ultimately leading to its release from the bamboo. Furthermore, the presence of H-type lignin-FA-arabinoxylan linkage structures within the bamboo LCC was identified with their primary dissolution observed in the S-layer of the bamboo fiber cell walls. The study results provided a clear target for breaking down the anti-depolymerization barrier in bamboo, signifying a major advancement in achieving the comprehensive separation of bamboo components.

A huge amount of lignocellulosic agro-food processing wastes (AFWs) is produced by agricultural practices and food industries. Coffee silverskin (CSS) is an AFW produced during the coffee bean–roasting process. Pretreatment methods are required to promote the enzymatic hydrolysis of AFWs, including CSS, aimed at their use as feedstock in a sugar-based biorefinery. A combined pretreatment, based on ultrasound and mild alkaline solution, has been optimized for CSS. The effects of sonication time, biomass loading, NaOH concentration and alkaline pretreatment residence time were investigated according to the response surface methodology. The maximum sugar yield (YS = 0.6 g g sugars in pretreated CSS−1) was obtained after enzymatic hydrolysis of CSS pretreated with 5-min sonication at 11% w v−1 biomass loading, and 75-min autoclave in 5% w v−1 NaOH. Fermentation inhibitors in the pretreatment solvent were absent or present at concentrations not affecting the growth of Clostridium sp. relevant for biofuel production. The phenolic content was 25 mgGAE graw_CSS−1. [ABSTRACT FROM AUTHOR]

Hydrolysis is the heart of the lignocellulose-to-bioethanol conversion process. Using enzymes to catalyze the hydrolysis represents a more environmentally friendly pathway compared to other techniques. However, for the process to be economically feasible, solving the product inhibition problem and enhancing enzyme reusability are essential. Prior research demonstrated that a flat-sheet membrane bioreactor (MBR), using an inverted dead-end filtration system, could achieve 86.7% glucose yield from purified cellulose in 6 h. In this study, the effectiveness of flat-sheet versus radial-flow MBR designs was assessed using real, complex lignocellulose biomass, namely date seeds (DSs). The tubular radial-flow MBR used here had more than a 10-fold higher membrane surface area than the flat-sheet MBR design. With simultaneous product separation using the flat-sheet inverted dead-end filtration MBR, a glucose yield of 10.8% from pretreated DSs was achieved within 8 h of reaction, which was three times higher than the yield without product separation, which was only 3.5% within the same time and under the same conditions. The superiority of the tubular radial-flow MBR to hydrolyze pretreated DSs was confirmed with a glucose yield of 60% within 8 h. The promising results obtained by the novel tubular MBR could pave the way for an economic lignocellulose-to-bioethanol process.

Fresh-harvested, air-dried rice straw was pretreated at a water content of 5 g H2O/g straw using sodium hydroxide (NaOH) and compared to pretreatment at 10 g H2O/g straw by hydrated lime (Ca(OH)2). Full factorial experiments including parallel wash-only treatments were completed with both sources of alkali. The experiments were designed to measure the effects of alkaline loading and pretreatment time on delignification and sugar yield upon enzymatic hydrolysis. Reaction temperature was held constant at 95°C for lime pretreatment and 55°C for NaOH pretreatment. The range of delignification was 13.1% to 27.0% for lime pretreatments and was 8.6% to 23.1% for NaOH pretreatments. Both alkaline loading and reaction time had significant positive effects (p

Abstract Rice husk (RH) is the major agricultural waste obtained during rice hulling process, which can be a sustainable source of xylooligosaccharide (XOS). The current study deals with the production of XOS from Thai rice husk using alkaline pretreatment and enzyme hydrolysis method. The response surface methodology consisted of central composite design and Box–Behnken design was employed to achieve the maximum response in alkaline pretreatment and XOS production, respectively. The optimum conditions for alkaline pretreatment to recover maximum xylan yield were 12–18% of alkaline concentration, the temperature at 110–120 °C, and steaming time for 37.5–40 min. The FTIR results suggested that the extracted sample was the xylan fraction. The maximum XOS production of 17.35 ± 0.31 mg XOS per mL xylan was observed in the run conditions of 6.25 mg enzyme per g xylan, 9 h of incubation time, and 5% of xylan. The results revealed that the xylan extracted from RH by using an effective base couple with the steam application and the enzymatic hydrolysis help to maximize the yield of XOS, which can be further used in functional foods and dietary supplements.

Background: Pretreatment of lignocellulosic biomass is essential for using it as a raw material for chemical and biofuel production. This study evaluates the effects of variables in the chemical pretreatment of the Arundo biomass on the glucose and xylose concentrations in the final enzymatic hydrolysate. Three pretreatments were tested: acid pretreatment, acid pretreatment followed by alkaline pretreatment, and alkaline pretreatment. Results: The amounts of glucose and xylose released by the enzymatic hydrolysis of the Arundo biomass obtained from acid pretreatment ranged from 6.2 to 19.1 g/L and 1.8 to 3.1 g/L, respectively. The addition of alkaline pretreatment led to a higher yield from the enzymatic hydrolysis, with the average glucose concentration 3.5 times that obtained after biomass hydrolysis with an acid pretreatment exclusively. The use of an alkaline pretreatment alone resulted in glucose and xylose concentrations similar to those obtained in the two-step pretreatment: acid pretreatment followed by alkaline pretreatment. There was no significant difference in 5-hydroxymethylfurfural, furfural, or acetic acid concentrations among the pretreatments. Conclusion: Alkaline pretreatment was essential for obtaining high concentrations of glucose and xylose. The application of an alkaline pretreatment alone resulted in high glucose and xylose concentrations. This result is very significant as it allows a cost reduction by eliminating one step.

Copyright of Transactions of China Pulp & Paper is the property of China Pulp & Paper Magazines Publisher and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Herein, sodium hydroxide (NaOH) pretreatment of lignocellulose is performed to investigate the structural evolution of lignin, cellulose, and hemicellulose. It is found that most of hemicellulose and part of cellulose are hydrolyzed/converted to monosaccharide, alcohols, and carboxylic acids. Over half of cellulose is stabilized because the reducing end groups of cellulose convert to stable carboxylic groups. In addition, lignin is converted to aromatic monomers (predominately vanillin and acetovanillone) with a highest yield of 6.1 wt%, along with dimers and oligomers with Mw less than 10 000 Da. According to heteronuclear single quantum coherence analysis, no common interlinkages (β-O-4, β-β, β-5, etc.) appear in lignin oligomers due to lignin fragments condensed during the alkaline pretreatment. Notably, the acidification process is also the cause of lignin condensation since high aromatic monomers yield of 15 wt% (based on original lignin in pine) is achieved by a postoxidation of alkaline solution, while few no aromatic monomers generated by using the isolated lignin oligomers. The direct oxidation of lignocellulose in alkaline solutions to aromatic monomers demonstrates the potential application of lignocellulose alkaline pretreatment for high-value chemicals production. [ABSTRACT FROM AUTHOR]

The lignocellulosic biomass, such as provided by the sugarcane, is an abundant source of raw materials for energy production. Milling and pretreatments can be employed to alter the structure of the materials, remove lignin, and hemicellulose. This pretreatment effect exposes the cellulose and raises its accessibility, which is one of the most important properties to ensure enzymatic digestibility. However, the biomass generated from the sugarcane has different physicochemical characteristics, giving different responses to the pretreatments. In this context, this study aimed to verify the effects of lignin and hemicellulose removal from the sugarcane biomass (external fraction, node, internode, and leaf) on cellulose accessibility. Each fraction was pretreated with acid (5, 10, and 20% w/w, at 121 °C/30 min), alkali (5, 10, 20, and 30% NaOH w/w) and oxidative (0.5, 1, 2, and 3 h charged with 30% sodium chlorite). Accessibility was determined by dye adsorption of Direct Orange (external specific surface) and Direct Blue (internal specific surface). Enzymatic hydrolysis was used to verify the effects of pretreatments and cellulose accessibility on the glucose yield. Delignification by sodium chlorite (oxidative) resulted in lignin removal, with almost complete removal from leaf samples. Accessibility determined indicated that pretreatments that are more aggressive improved cellulose accessibility. The less recalcitrant fraction, the internode, showed 1333.3 mg/g of Direct Orange adsorbed and 746.3 mg/g of Direct Blue. Glucose yield during enzymatic hydrolysis improved with higher cellulose accessibility. Lignin and xylan removal (down to 10% and 1%, respectively) resulted in higher glucose yield, with delignified internode samples showing almost complete cellulose conversion. Hemicellulose and lignin removal by the pretreatments directly influenced cellulose accessibility, resulting in better enzymatic hydrolysis across all fractions. This study successfully showed that lignin and hemicellulose removal of 15% and 10%, respectively, resulting in at least 60% of glucose yield, reaching desired accessibility levels based on dye adsorption of 2079.6 mg/g. [ABSTRACT FROM AUTHOR]

In this study, the acidification and two-phase anaerobic digestion (AD) were conducted in batch and continuous stirred tank reactors, respectively, to determine the effect of acidification on methane production in AD. The results showed that two-phase AD achieved an observable enhancement in the methane production under optimal acidification conditions (organic loading rate of 60 g TS/L, the ratio of raw material to inoculum (based on dry weight) of 2:1, the temperature of 45°C, urea concentration of 4%, and time of 6 d). Under these conditions, the daily biogas and biomethane productions were 0.48 L/g TS and 0.30 L/g TS, respectively, which were 26.32% and 57.89% higher than those of the untreated group, respectively. The ammonia nitrogen (AN), alkalinity, and pH value of the methanogenic phase of C4 continued to increase up to 956 mg/L, 5680 mg/L, and 7.41, respectively, after 60 d, which might have destroyed the stability of the system. Therefore, for the purpose of reusing the nitrogen source, reducing AN, and maintaining the stability of the reaction system, another set of acidification and two-phase AD with water pretreatment using the discharge of the methanogenic phase of C4 as the inoculum was subsequently conducted. The results showed that the daily biogas productions of single-phase and two-phase AD were 5.26% and 15.79% higher than that of the untreated group, respectively; similarly, their daily methane yields were 10.42% and 21.05% higher than that of the untreated group. [ABSTRACT FROM AUTHOR]

The residual peels of andiroba seeds were submitted to alkaline pretreatment that aimed to maximize the recovery of fermented sugar. Evaluation of the best operation performance via the reaction time variables (20, 60, and 100 min), NaOH concentration (2, 3, and 4% (m/v)), and temperature (60, 90, and 120 °C) at a fixed solids concentration of 5% (m/v) was performed. A Box-Behnken experimental design was used. Lignocellulosic material was characterized by cellulose (30.57 ± 1.00%), hemicellulose (15.08 ± 0.65%), lignin (36.02 ± 1.05%), extractives (7.49 ± 0.03%), and ash (1.53 ± 0.28%). The optimization was performed using the response surface methodology approach. The model provided a coefficient of determination (R²) of 0.95. The predicted optimal conditions for the process were a reaction time of 100 min, NaOH concentration of 4% (m/v), and temperature of 120 °C, which allowed the authors to obtain a saccharification of approximately 47.9%. [ABSTRACT FROM AUTHOR]

In the past few years, the global demand in bioethanol has been continuously rising due to its economic importance. Several countries have exerted considerable efforts in the production of bioethanol as a transport fuel from different feedstocks and started to practice consuming this environment-friendly fuel. Thailand is now one of the top consumers of bioethanol in South East Asia and belongs to the top 5 leading countries in producing pineapples. Production of bioethanol from pineapple wastes, especially the fruit peels, became possible. In this study, the effects of alkaline pretreatment and microbial hydrolysis through Trichoderma harzianum of pineapple fruit peel were evaluated. Among the four concentrations of NaOH, the 0% NaOH gave the highest total and reducing sugar (458.44 ± 13.6 g/L and 279.67 ± 21 g/L) than 1%, 3%, and 5% concentrations of NaOH. Samples pretreated with 0% NaOH were subjected to microbial hydrolysis which showed an increase in reducing sugar of the samples. At the end of the experiment, a bioethanol yield of 5.98 ± 1.01 g/L from pineapple fruit peel was successfully produced at 48 h of fermentation. [ABSTRACT FROM AUTHOR]

Oil palm empty fruit bunch (OPEFB) is one of the prominent lignocellulosic wastes from the oil palm industry, and it has the potential for feedstock in biobased products. However, delignification must be applied. This study investigated the effect of microwave-assisted alkaline pretreatment of OPEFB by using response surface methodology with Box-Behnken design (BBD) to find the optimum pretreatment conditions. OPEFB (30-mesh) was treated with various concentrations of aqueous sodium hydroxide. The effect of three variables, microwave power (280-840 W), NaOH concentration (1-3% w/v), and reaction time (3-9 min), was evaluated to improve lignin removal. The quadratic model indicated that microwave power of 832.9 W, NaOH concentration of 2.7% (w/v), and a reaction time of 8.9 min resulted in the highest lignin removal: 88.10%. FTIR and SEM analysis was also conducted on the untreated and treated OPEFB to evaluate the effectiveness of the pretreatment. These results showed that microwave-assisted alkaline pretreatment of OPEFB could effectively remove the lignin under a relatively short time period and low alkaline concentration. [ABSTRACT FROM AUTHOR]

Nowadays, more and more attention is paid to the development and the intensification of the use of renewable energy sources. Hemp might be an alternative plant for bioenergy production. In this paper, four varieties of Polish industrial hemp (Białobrzeskie, Tygra, Henola, and Rajan) were investigated in order to determine which of them are the most advantageous raw materials for the effective production of bioethanol. At the beginning, physical and chemical pretreatment of hemp biomass was carried out. It was found that the most effective is the alkaline treatment with 2% NaOH, and the biomasses of the two varieties were selected for next stages of research: Tygra and Rajan. Hemp biomass before and after pretreatment was analyzed by FTIR and SEM, which confirmed the effectiveness of the pretreatment. Next, an enzymatic hydrolysis process was carried out on the previously selected parameters using the response surface methodology. Subsequently, the two approaches were analyzed: separated hydrolysis and fermentation (SHF) and a simultaneous saccharification and fermentation (SSF) process. For Tygra biomass in the SHF process, the ethanol concentration was 10.5 g∙L−1 (3.04 m3·ha−1), and for Rajan biomass at the SSF process, the ethanol concentration was 7.5 g∙L−1 (2.23 m3·ha−1). In conclusion, the biomass of Polish varieties of hemp, i.e., Tygra and Rajan, was found to be an interesting and promising raw material for bioethanol production.

Abstract Background Heterogeneity within herbaceous biomass can present important challenges for processing feedstocks to cellulosic biofuels. Alterations to cell wall composition and organization during plant growth represent major contributions to heterogeneity within a single species or cultivar. To address this challenge, the focus of this study was to characterize the relationship between composition and properties of the plant cell wall and cell wall response to deconstruction by NaOH pretreatment and enzymatic hydrolysis for anatomical fractions (stem internodes, leaf sheaths, and leaf blades) within switchgrass at various tissue maturities as assessed by differing internode. Results Substantial differences in both cell wall composition and response to deconstruction were observed as a function of anatomical fraction and tissue maturity. Notably, lignin content increased with tissue maturity concurrently with decreasing ferulate content across all three anatomical fractions. Stem internodes exhibited the highest lignin content as well as the lowest hydrolysis yields, which were inversely correlated to lignin content. Confocal microscopy was used to demonstrate that removal of cell wall aromatics (i.e., lignins and hydroxycinnamates) by NaOH pretreatment was non-uniform across diverse cell types. Non-cellulosic polysaccharides were linked to differences in cell wall response to deconstruction in lower lignin fractions. Specifically, leaf sheath and leaf blade were found to have higher contents of substituted glucuronoarabinoxylans and pectic polysaccharides. Glycome profiling demonstrated that xylan and pectic polysaccharide extractability varied with stem internode maturity, with more mature internodes requiring harsher chemical extractions to remove comparable glycan abundances relative to less mature internodes. While enzymatic hydrolysis was performed on extractives-free biomass, extractible sugars (i.e., starch and sucrose) comprised a significant portion of total dry weight particularly in stem internodes, and may provide an opportunity for recovery during processing. Conclusions Cell wall structural differences within a single plant can play a significant role in feedstock properties and have the potential to be exploited for improving biomass processability during a biorefining process. The results from this work demonstrate that cell wall lignin content, while generally exhibiting a negative correlation with enzymatic hydrolysis yields, is not the sole contributor to cell wall recalcitrance across diverse anatomical fractions within switchgrass.

Introduction: Safflower straw is one of the agricultural residues that currently have no specific use. So, it can be used as a cheap source for biofuel production. Materials and methods: Alkaline pretreatment with NaOH was used to improve enzymatic hydrolysis, ethanol, and biogas production from safflower straw. The pretreatment was performed with 8% (w/v) NaOH solution at two different temperatures (0 and 100 °C) for 10-60 min. The liquid fraction of the pretreatment was subjected to anaerobic digestion for methane production. Solid fraction obtained from the pretreatments was used for bioethanol and biogas production in a parallel process. Therefore, two routes were followed for energy production from safflower straw: (1) ethanol production from solid fraction (2) biogas production from liquid fraction. In order to optimize the production of biofuels and compare different pretreatment conditions, the gasoline equivalents were calculated based on one tone of safflower straw after all pretreatment conditions. Statistical validation of the results was carried out using Minitab 16 software. Results: The highest glucose and ethanol production yields were obtained after the pretreatment at 100°C for 60 min. The glucose yield from untreated straw was only 20.6% and improved to 84.5%, whereas the corresponding ethanol yield was improved from 10.8% to 83.2%. The best improvement in methane production from solid fraction was achieved by pretreatment at 0 °C for 60 min, and resulted in 191.4 ml/g VS which was 99.6% higher than methane yield obtained from untreated straw. The highest gasoline equivalent was 124.9 L obtained after pretreatment at 0 oC for 60 min. Discussion and conclusion: Enzymatic hydrolysis and ethanol yields from the safflower straw were improved more by the pretreatment at high temperature. However, low temperature is desirable for methane production.

The complete utilisation of Dried Distillers Grains with Solubles (DDGS) requires effective pretreatment strategies aiming to increase the enzymatic digestibility of cellulose and improve its conversion to fermentable sugars. To this end, the effect of different NaOH concentrations (0–5%, w/v) and temperature (30–121 °C) on the fractionation of DDGS to its main components (cellulose, hemicellulose, proteins) was evaluated. As the NaOH concentration and temperature increased, the total sugar content of the pretreated DDGS solids progressively increased to a maximum of ∼88%. At 121 °C and 5% NaOH, the DDGS solid residue consisted primarily of glucose (∼53%), a 5-fold increase compared to the original DDGS, reflecting the presence of cellulose, and to a lesser extent by xylose (∼25%) and arabinose (∼10%) reflecting the presence of hemicellulose. Approximately 83% of the initial hemicellulose and 79% of the protein contents were removed into the liquid fraction during alkaline pretreatment. The enzymatic digestibility of the pretreated DDGS solids by the Accellerase® 1500 cellulase enzyme was significantly improved, resulting in a 3.6 fold increase in glucose yield compared to untreated DDGS. Mass balance analysis demonstrated that the proposed process scheme recovers the majority of the key DDGS components (cellulose, hemicellulose, proteins) in an efficient manner with relatively low losses, and provides a viable approach for the valorisation of DDGS. [ABSTRACT FROM AUTHOR]

Rice straw, an abundant agro-residue, is available for energy production. In many parts of Asian countries, it is burnt on fields causing harm to the environment. Rice straw contains lignin, cellulose, hemicelluloses, and silicates making it recalcitrant. Pretreatment processes disintegrate lignin-carbohydrate matrix for efficient bioconversion of polysaccharides to fermentable sugars. A good number of physical, biological and chemical processes have been tried but degradation of polysaccharides and subsequent fermentation is still a challenge. Alkaline pretreatment causes effective delignification and swelling of biomass. The present study was performed on alkaline pretreatment of rice straw with 1% NaOH by autoclaving for 30 min at 121 °C at 10% solid loading. It was extracted with water to remove lignins, solids separated by filtrations and washed again to neutralize the pH. Water washing also led to removal of phenolic inhibitors. High (63%) glucan enrichment was obtained with concomitant lignin loss. Dry matter loss was around 50%. Enzymatic saccharification of the pretreated solids at 5 and 10% with Accellerase® 1500 for 24 h at 50 °C gave saccharification efficiency 76 and ~ 50% respectively. Hydrolysates containing 18 and 23 gL−1 sugars, supplemented with minimal salts, yeast extract, fermented by S. cerevisiae LN for 24 h yielded ~ 2 and 4 gL−1 ethanol with fermentation efficiency 55–66%. Thus, NaOH pretreatment is a cost effective option for ethanol production from rice straw. Lignin removed in prehydrolysates can be recovered by acidification. [ABSTRACT FROM AUTHOR]

The sugar cane bagasse constitutes an abundant lignocellulosic agro-industrial residue in Cuban sugar industry. However, its complex structure partially limits biodegradation, for that reason it is necessary to apply a pretreatment, being the alkaline the most effective for biomasses with a high lignin content. This work objective is to evaluate the effect of alkaline pretreatment in cane bagasse delignification, and its anaerobic biodegradability with respect to without pretreatment bagasse. Two alkalis (NaOH and KOH) with two concentration levels (0.5 and 1% w/v), and two contact times (1 and 3 h), were studied at room temperature. Results were evaluated in terms of % delignification, methane yield and process kinetics according to a first order model. Maximum lignin reduction (36.5%) and methane yield (192 mLCH4/g VS) were obtained with NaOH (0.5% -3h), achieving a 94.6% increase in methane yield respect to without pretreating bagasse. Kinetic study confirmed that kinetic parameters are improved compared to without pretreatment bagasse, with this variant. [ABSTRACT FROM AUTHOR]

Pretreatment processes play an important role in the conversion of lignocelluloses materials to reducing sugar for ethanol production. They help in breaking the structure of lignin and disrupt the crystalline structure of cellulose and hemicellulose, thus improving enzymatic accessibility during hydrolysis. In this study, various alternatives to pretreat oil palm empty fruit bunches (OPEFB), oil palm frond (OPF) and oil palm trunk (OPT) were investigated for improving enzymatic digestibility and fermentable sugars production. The most suitable method was superheated steam explosion followed by alkaline autoclaving pretreatment (SSE–AA). The superheated steam explosion was performed at 180 °C and 0.6 MPa for 5 min (severity factor 3.05), followed by treating with 2–20% (w/v) NaOH at 121 °C for 10–60 min in an autoclave. The SSE–AA treated OPEFB, OPF and OPT had cellulose contents 73.1, 68.7 and 65.3%, respectively. In addition, the enzymatic digestibilities of the treated OPEFB, OPF and OPT pulps were 90.0, 85.15 and 68.73%, respectively, while their glucose yields were 0.90, 0.85 and 0.69 g/g, which were 13.43, 12.35 and 33.71 fold higher than with untreated pulps. Scanning electron microscopy showed that the SSE–AA pretreatment strongly disrupted the fiber structure by removing the cell wall, hydrolyzing both lignin and hemicelluloses, causing swelling and partial rupture of the fibers. [ABSTRACT FROM AUTHOR]

BACKGROUND Taraxacum kok‐saghyz (TK) is a rubber‐producing plant being developed as a commercial alternative source of natural rubber (NR). The objective of this study was to investigate processes to extract high quality NR at high yield and purity from TK. Rubber is formed in the roots of TK and exists in mostly solid form. Previously used mechanical processes extract NR from TK roots at low purity (< 90%) that does not meet industry standards (≥ 99.8%). To improve this, the effects of root chopping, enzymatic hydrolysis, pebble milling and alkaline pretreatment and purification on NR yield, purity and quality were investigated. RESULTS: Enzymatic digestion (with and without alkaline pretreatment), yielded rubber at the highest yield (∼80%) and purity (99.4%). Alkaline pretreatment of roots improved NR yield and did not adversely affect quality. More rubber was extractable from chopped roots than whole roots, but the rubber was less pure. Alkaline purification of the extracted crude rubber further increased rubber purity but reduced rubber molecular weight. CONCLUSION: Enzymatic digestion with or without alkaline pretreatment forms the basis of aqueous processes that could be used for large‐scale, efficient extraction of TK rubber at high yield, purity and quality to meet industry standards for NR. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Eucalyptus wood was pretreated with an integrated process based on hydrothermal and alkaline pretreatments. The structural changes of hemicelluloses during the pretreatments and the components of the hydrolysates were comprehensively characterized. Sugar and spectral analyses indicated that the hemicelluloses remained in the residues obtained at hydrothermal pretreatment under low temperatures were mainly composed of a (1 → 4)- β -D-Xyl p backbone with 4- O -methyl- α -D-glucuronic acids attached at O -2 of the xylose together with various monosaccharides of rhamnose, arabinose, galactose, glucose, and mannose. The pretreatments resulted in serious degradation of hemicelluloses at high pretreatment temperatures. The distribution changes of the hemicelluloses in the cell walls during the integrated pretreatments were detected by Confocal Raman Microscopy, which revealed that the dissolution of hemicelluloses in different morphological regions was inhomogeneous, and the a large portion of hemicelluloses were removed from the secondary cell wall regions during the pretreatments. Unlabelled Image • Hydrothermal and alkaline pretreatments were proposed to treat Eucalyptus wood. • The H 0 and H 170 have a linear backbone of (1 → 4)- β -D-Xyl p residues. • The dissolution of hemicelluloses in different morphological regions was uneven. • The hemicelluloses were dissolved mostly from the secondary cell wall regions. [ABSTRACT FROM AUTHOR]

This study aimed to analyze the coupled effect of electromagnetic microwave radiation and sodium hydroxide on the structure of a lignocellulosic complex of Virginia mallow and to determine the susceptibility of the pretreated substrate to anaerobic degradation. Effects of substrate digestion with conventional and microwave heating were compared as well. NaOH dose increase from 0.02 g·g t.s −1. to 0.2 g·g t.s −1. caused biogas production to increase in both heating variants. In turn, NaOH dose increase to 0.4 g·g t.s −1. resulted in diminished biogas production in variants with both microwave and conventional heating, i.e. by 15.3% and 20.8%, respectively. The highest biogas production effectiveness was achieved during fermentation of the substrate conditioned using microwave radiation coupled with the addition of NaOH in a dose of 0.2 g·g t.s −1., and the result obtained was by 10% higher compared to the conventionally-heated sample and by 39.4% higher compared to the microwave-heated and chemically-untreated sample. The coupled use of microwave heating and alkaline treatment allowed achieving a higher volume of biogas produced. Methane content in gaseous bacterial metabolites ranged from 58 to 61%, irrespective of NaOH dose and heating method. • The highest biogas production was obtained after microwave heating with NaOH in a dose of 0.2 g/g t.s. • The coupled use of pretreatment methods allowed achieving a higher volume of biogas produced. • Methane fermentation inhibition observed could be due to the excess of Na+ ions. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Sweet corn co-products pretreated in twin screw extruder with sodium hydroxide. • Temperature can improve alkali effects on hemicelluloses solubilization and enzymatic hydrolysis. • High temperatures and alkaline loadings limit filtration step within extruder. • Continuous pretreatment reach 500 g of fermentable sugars per 1 Kg of dry SCC. Abstract A continuous process combining an alkaline pretreatment, neutralization and injection of enzymes within a twin screw extruder was previously implemented and demonstrate industrial potential. The present work focuses on the investigation of the effects of alkali and temperature during the alkaline pretreatment of sweet corn co-products (SCC) for the production of fermentable sugars with a lower chemical input. Study of NaOH/SCC and internal temperature was performed in ranges of 4–8% (w/w) and 50–170 °C in a laboratory scale twin screw extruder. Analysis of carbohydrates and lignin of the pretreated biomass was performed and the filtration efficiency was also monitored through extrudate dry matter and filtrate mineral matter. The carbohydrate accessibility and process performances were studied by the enzymatic hydrolysis of the extrudate. Increasing temperature reinforces the effects of soda on solubilization of hemicelluloses, thus a hemicelluloses removal reach more than 50%. At optimal conditions, the cellulose-rich substrate after enzymatic hydrolysis achieve a glucose released of 70%, with glucose and xylose yields of 250 g per 1Kg of dry SCC. [ABSTRACT FROM AUTHOR]

A slag humidification process that aims to reduce the leachate pH of steel slag via carbonation was accomplished by simply wetting the slag and exposing it to the atmosphere for passive diffusion of atmospheric CO 2. The optimization parameters of the process were studied. Results showed that by wetting the slag using various aqueous solutions (deionized water, NaCl solution and NaOH solution), such that its moisture content nearly reaches its water holding capacity, a significant reduction in leachate pH could be achieved. Pretreatment of the slag using 1 M NaOH and subsequent humidification using deionized water showed the best efficiency of 1.1 pH unit reduction among the tested conditions. Slag pretreatment could substantially enhance the carbonation degree on the slag surface, leading to conservation of the treatment effectiveness up to three times the leachate replenishment using deionized water. The benefit of the alkaline treatment to promote slag carbonation could also be achieved using a low to moderate (0.005–0.1 M) NaOH solutions for humidification without the pretreatment step. A 72.5% increase in the treatment efficiency could be achieved via a humidification treatment using 0.005 M NaOH solution compared to that using deionized water. This study shows the promise of humidification treatment as a low-cost, easily implemented, and environmentally friendly slag pH neutralization process that can be applied in the field for slag treatment prior to its use or disposal in the environment. Unlabelled Image • A humidification treatment was optimized for slag pH neutralization. • Up to a 1.1-unit pH reduction was achieved via passive slag carbonation. • Alkaline pretreatment greatly improved the humidification efficiency and stability. • Humidification using alkaline solutions may be applied in lieu of pretreatment. • Freshwater salinity is optimal in terms of humidification efficiency. [ABSTRACT FROM AUTHOR]

Non-mammalian collagens have attracted increasing attention for industrial and biomedical use. We have therefore evaluated extraction conditions and the biochemical properties of collagens from aquacultured sturgeon. Pepsin-soluble type I and type II collagen were respectively extracted from the skin and notochord of bester sturgeon by-products, with yields of 63.9 ± 0.19% and 35.5 ± 0.68%. Collagen extraction efficiency was improved by an alkaline pretreatment of the skin and notochord (fewer extraction cycles were required), but the final yields decreased to 56.2 ± 0.84% for type I and 31.8 ± 1.13% for type II. Alkaline pretreatment did not affect the thermal stability or triple-helical structure of both types of collagen. Types I and II collagen formed re-assembled fibril structures in vitro , under different conditions. Alkaline pretreatment slowed down the formation of type I collagen fibrils and specifically inhibited the formation of thick fibril-bundle structures. In contrast, alkaline pretreatment did not change type II collagen fibril formation. In conclusion, alkaline pretreatment of sturgeon skin and notochord is an effective method to accelerate collagen extraction process of types I and II collagen without changing their biochemical properties. However, it decreases the yield of both collagens and specifically changes the fibril-forming ability of type I collagen. Unlabelled Image • We evaluated extraction conditions and the biochemical properties of collagens from by-products of aquacultured sturgeon. • Alkaline pretreatment accelerated collagen solubilization, but decreased collagen yields in types I and II collagen. • Alkaline pretreatment had no effects on the thermal stability and triple helical structure of two types of collagen. • Alkaline pretreatment slowed down fibrillogenesis of type I collagen and inhibited the formation of thick fibril-bundle structures. [ABSTRACT FROM AUTHOR]

Abstract Four different lignin samples were isolated during the processing of rice straw for ethanol production: one after mild alkaline pretreatment (deacetylation) of rice straw, and other three after simultaneous saccharification and fermentation (fermentation residues), under different process conditions. Then, a complete chemical characterization in terms of main components (lignin, carbohydrates, among others) and elemental composition was performed for all the samples. Additionally, the structural and morphological characteristics, calorific value, thermal stability, solubility in solvents and antioxidant potential were also determined. For comparison, a standard lignin (Kraft lignin) was also assayed. The results revealed that the process used for lignin isolation has an important influence in the final properties of the sample. In general, the fermentation residues contained non-hydrolyzed polysaccharides in their composition and lower lignin content when compared to the lignin solubilized in the alkaline liquor. Among several organic solvents and mixtures, acetone 80% (v /v) was the most efficient for lignin solubilisation. Interesting properties and characteristics were observed for all the lignin samples isolated from rice straw processing, which would allow their application in different industrial areas. Based on the properties, potential applications were suggested, which could be of value for integration in biorefineries. Highlights • Lignin samples were isolated during the rice straw processing to produce ethanol. • The process used for isolation influenced the final properties of the lignin sample. • Acetone 80% (v/v) was a very efficient solvent for lignin solubilisation. • Potential applications were suggested according to the properties/characteristics of the sample. [ABSTRACT FROM AUTHOR]

The effects of microwave and steam mediated pretreatments were evaluated and compared relative to the hydrolysis of sweet sorghum bagasse (SSB) in the presence of sodium hydroxide. The results established the optimum parameters for energy consumption and sugar production after hydrolysis of the pretreated SSB. The energy balance was better in microwave treatment compared with the steam treatment. The results recommended pretreatment at 300 watts power setting in the microwave oven up to 10 min. At higher wattage setting and longer exposure time, increased sugar yields were obtained, although the efficiency of the process decreased when the energy balance was calculated. The energy balance was calculated as the proportion of energy consumed during the pretreatments to the energy that can be produced by fermenting released glucose to ethanol. In this study, the energy consumed during the different pretreatments varied from 1/33 to 1/200 of the energy obtainable by fermenting released glucose to ethanol. Overall, the pretreatment of SSB to produce fermentable sugars was effective, and the energy balance was positive both in microwave and steam pretreatments of alkaline suspension of SSB. In microwave treatment the energy applied can be more accurately dosed, and consequently the energy balance was improved compared to steam treatment. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Alkaline pretreatment alone increased methane yield of rice straw by 60%. • Alkaline pretreatment with magnetite nanoparticles increased methane yield by 129%. • Energy assessment indicated a positive net gain for this treatment. Abstract Agricultural residues have high potential for biogas production, complex lignocellulosic structure is however the main hindrance in their bioconversion. This research focuses on combined effect of alkaline pretreatment of rice straw and magnetite (Fe 3 O 4) nanoparticle application. Four doses of magnetite nanoparticles viz. 60, 80, 100 and 120 ppm were used in the anaerobic digestion of untreated and 2% NaOH pretreated rice straw. Compared to control, 2% NaOH pretreatment alone increased biogas and methane yield by 57 and 60% respectively. Magnetite nanoparticle (MNP) application alone gave maximum yield at 100 ppm which consisted of 37 and 33% more biogas and methane yield respectively. Combining the effect of 2% NaOH pretreatment and 120 ppm MNPs synergistically increased biogas and methane yield by 100 and 129% as compared to control. In addition, an energy assessment indicated a positive net gain of 3765 kJ for 2% NaOH pretreated rice straw with 120 ppm MNPs. [ABSTRACT FROM AUTHOR]

Abstract Currently, cellulose nanostructures (CNS) are obtained using pretreatments of lignocellulosic residues. In this work, different conditions in the enzymatic isolation process were studied to obtain CNS, aiming an alternative eco-friendly method. Two isolation methodologies were used: a) one submitting the residue to an alkaline pretreatment and b) other using the lignocellulosic waste directly without pretreatment. A commercial complex of enzymes (Ctec®) was used, varying the time to which the substrate was exposed to the enzymes at 12, 24 and 48 h, searching for the better condition to CNS obtaining. The application of alkaline pretreatment removed 73% of hemicellulose and 50% of lignin from wood fiber leading to a more exposed cellulose structure and increased the amount of nanocellulose produced. The obtained nanostructures were needle-shaped of approximately 70 nm wide. However, CNS of similar size and shape were received as well without pretreatment application, allowing their obtainment with lower reagent consumption through a more environmentally efficient route, as presented in the life cycle impact assessment (LCIA) where energy consumption and acidification potential were considered. Graphical abstract Image Highlights • Cellulosic nanostructures were obtained by enzymatic hydrolysis without pretreatment. • Time of reaction affects only the yield, not the mean size of the structures. • Needle-like structures with higher crystallinity were obtained without pretreatment. • Pretreatment surpassing reduced the impacts represented in the LCIA. [ABSTRACT FROM AUTHOR]

Abstract Biological valorization of biomass most often depends on the efficient reduction of plant cell wall recalcitrance and conversion of lignin – the most recalcitrant constituent – to fuels, chemicals and/or value-added substances. Lignin conversion to fuels and value-added chemicals requires a sound understanding of the structure of lignin before and after different pretreatments. In the current work, an effort has been made to compare the structural differences in isolated pine lignin after one- (alkaline) and two-step (alkaline/dilute acid and alkaline/steam explosion) pretreatments. Our results indicate removal of the low molecular weight fraction of lignin after an initial alkaline pretreatment. A subsequent dilute acid pretreatment resulted in the loss of lignin inter-unit linkages such as β-O-4' aryl ethers. However, with a steam explosion pretreatment, lignin exhibited a competing condensation process leading to increased condensed lignin structures. Graphical abstract Isolation and molecular level identification of structures of pine lignin. Image 1 Highlights • Structure of pine lignin after two-stage pretreatments. • Pretreated lignin is altered by depolymerization-repolymerization processes. • NMR analysis of pretreated lignin highlights changes in lignin structure. [ABSTRACT FROM AUTHOR]

Alkaline pretreatment was employed to enhance biogas production from asparagus stover with anaerobic digester in laboratory scale batch fermentation. Different pretreatment times (10, 18, 25 days), NaOH concentrations (2.5, 5, 7.5%), and water dose (20, 60, 100 mL) were tested to select the best pretreatment conditions. With response surface method (RSM) applied, the optimum pretreatment conditions were pretreatment time of 19d, NaOH concentration of 4.2%, water dose of 74 g.The biogas yield was predicted as 275.65 mL/g VS, while it was observed as 277.86 mL/g VS in the verification test, with the relative error of 0.80%. Further more, the verification tests show that contents of hemi-cellulose, cellulose and lignin after pretreatment were decreased by 65.20, 29.06 and 13.51%, respectively. The above results suggest that the effects of NaOH on degradations of hemi-cellulose and cellulose are higher than that on lignin. [ABSTRACT FROM AUTHOR]