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Alkaline pretreatment and sequential enzymatic hydrolysis of soybean hull were investigated to obtain fermentable sugars for polyhydroxyalkanoates production along with residual glycerol as low-cost carbon sources. Soybean hull is composed of approximately 32% cellulose, 12% hemicellulose, 6% lignin, and 11% protein. Alkaline pretreatment was carried out with 2% NaOH concentration, 10% (w/v) biomass loading, and 60 min incubation time in an autoclave at 120 °C. The response surface methodology (RSM) based on the central composite design (CCD) tool was employed to optimize the enzymatic hydrolysis process, where the variables of biomass loading, enzymes' concentration, and time were considered. The maximum total reducing sugars concentration obtained was 115.9 g∙L−1 with an enzyme concentration of 11.5 mg protein/g dry substrate for enzyme preparation B1, 2.88 mg protein/g dry substrate for XylA, and 57.6 U/g dry substrate for β-glucosidase, after 42 h at 45 °C, and pH was 4.5. Subsequently, the saccharification step was conducted by increasing the processing scale, using a 1 L tank with stirring with a controlled temperature. Implementing the same enzyme concentrations at pH 4.5, temperature of 45 °C, 260 mL working volume, and incubation time of 42 h, under fed-batch operation with substrate feeding after 14 h and 22 h, a hydrolysate with a concentration of 185.7 g∙L−1 was obtained. Initially, to verify the influence of different carbon sources on Cupriavidus necator DSMz 545 in biomass production, batch fermentations were developed, testing laboratory-grade glucose, soybean hull hydrolysate, and waste glycerol (a by-product of biodiesel processing available in large quantities) as carbon sources in one-factor-at-a-time assays, and the mixture of soybean hull hydrolysate and waste glycerol. Then, the hydrolysate and waste glycerol were consumed by C. necator, producing 12.1 g∙L−1 of biomass and achieving 39% of polyhydroxyalkanoate (PHB) accumulation. To the best of our knowledge, this is the first time that soybean hull hydrolysate has been used as a carbon source to produce polyhydroxyalkanoates, and the results suggest that this agro-industrial by-product is a viable alternative feedstock to produce value-added components. [ABSTRACT FROM AUTHOR]

Jatropha curcas is a promising tropical and subtropical plant species for biodiesel production that can reduce the competition between food and energy production. Jatropha seed processing for oil extraction usually generates considerable amount of Jatropha curcas fruit shell (JCFS), which can be considered as a potential substrate for biogas production rather than being discarded as solid waste. However, the higher lignocellulosic constituents in JCFS potentially affect the biological degradation process. Thus, applying suitable pretreatment techniques in advance of anaerobic digestion could enhance the biodegradability and methane yield of JCFS. In this study, the effect of mechanical, steam explosion (SE), and alkaline pretreatments on the chemical composition and methane yield of JCFS was examined at various process conditions. As compared with the untreated sample, grinding the JCFS into a particle size of less than 1 mm increased the methane yield by 74.23%, while at the optimum SE pretreatment process (160 °C, 5 min), the methane yield was increased by 54.75%. The alkaline pretreatment was relatively less effective over the other pretreatments; 44.05% methane yield increment was achieved after soaking the JCFS with 7.32% NaOH at 36 °C for 54 h. The effect of SE on compositional change depends on the severity factor in which severe pretreatment conditions were adequate for solubilizing the hemicellulose but resulted in higher pseudo-lignin and lower methane yields. In conclusion, all pretreatments processes have significantly increased the methane yield of JCFS as compared to the untreated JCFS; however, mechanical pretreatment was more effective than SE and alkaline pretreatments. [ABSTRACT FROM AUTHOR]

Agar is a hydrophilic biopolymer extracted from red seaweed. This phycocolloid consists of two components: agarose and agaropectin. In the present work, agar extracted from the invasive red seaweed Agarophyton vermiculophyllum was characterized using physical, chemical, and spectroscopic analyses to investigate the effect of alkaline pretreatment on agar properties. Two extraction conditions, native and alkali-pretreated agars, were comparatively studied. The native yield (28.4 ± 0.9%) was higher than that of the alkaline-pretreated agar (20.4 ± 0.8%). The alkali-pretreated agar showed higher gel strength (763.8 ± 57.0g cm−2), gelling (36.5 ± 0.9 °C), and melting (83.2 ± 0.6 °C) temperatures and increased 3,6-anhydrogalactose (26.2 ± 1.9%) and decreased sulfate contents (6.2 ± 0.8%) compared with native agar (gel strength: 204.8 ± 17.10g cm−2, gelling temperature: 29.5 ± 0.9 °C, melting temperature: 73.4 ± 0.7 °C, 3,6-AG content: 13.8 ± 0.7%, sulfate content: 10.5 ± 0.5%). The alkaline pretreatment improved the agar’s gelling properties and significantly influenced its chemical properties. In view of the obtained results, A. vermiculophyllum might potentially be thought of as a viable source for the agar industry in Morocco, serving as a local source of agar.

Conversion of Pennisetum purpureum × Pennisetum americanum (Napier Pak Chong1) press cake into biobutanol using Clostridium beijerinckii TISTR 1461 was proposed as an alternative to combustion in this study. The optimum conditions for biobutanol fermentation were determined using a full factorial design and a central composite design of experiment. The studied factors were initial pHs (5.50–6.50) and sugar concentrations (40–60 g/L), while butanol yield (g/g reducing sugar utilized) was specified as the optimization response. The results showed that the suitable enzyme loading of alkali-pretreated press cake (at 3% w/w NaOH, 10% substrate loading, boiling at 90 °C, with a reaction time of 1 h) was 10 FPU/g biomass, which provided a glucose yield of 345 mg/g pretreated press cake. The optimized pH and reducing sugar concentration were 6.08 and 43 g/L, respectively. At these conditions, the maximum butanol yield from the hydrolysate of NaOH-pretreated press cake was 0.135 g/g reducing sugar utilized (0.30 g/g glucose utilized). Apart from the possibility of generating much less pollution, it was estimated that using the same amount of press cake, butanol production could possibly have a value comparable to that obtained from combustion for electricity production. A new concept for overall Napier Pak Chong1 grass utilization was also presented.

Flax is one of the few plants that are entirely a source of raw materials for further production. Promising directions for the use of flax biomass may be the production of bioenergy in the form of 2G biofuels and the production of “green” composites. The aim of the study is to compare the biomass of fiber flax, linseed and dual-purpose varieties of cultivated flax (Linum usitatissimum L.) susceptibility to the biorefining processes. In the first stage of the research, based on the results of yield structure features and biometric measurements of plants, the most optimal flax line was selected for the fiber flax, linseed and dual purpose. Next, the forms of flax were pretreated with sodium hydroxide (NaOH), the chemical composition was determined and SEM images were taken. The obtaining of bioethanol process SFF (simultaneous saccharification and fermentation) was carried out. In addition, biodegradable polymers were modified with flax biomass, shapes were prepared, and the rheological and mechanical properties, as well as microbiological activity of biocomposites, were determined. The highest concentration of ethanol (8.72 g·L−1) and the greatest susceptibility to mold fungi of the biocomposites were obtained for the fiber flax variety PET 16/20.

The perennial rhizomatous grass giant reed (Arundo donax L.) can be exploited to produce hydrogen by dark fermentation. This implies a high availability of simple sugars, like glucose and xylose, and, thus, a pre-treatment is necessary to remove lignin and expose the holocellulose to enzymatic attack. This study aimed at evaluating the hydrogen production from giant reed hydrolysates. Giant reed dry meal was pre-treated with diluted NaOH (1.2% weight/weight), then the solid fraction was separated from the alkaline black liquor by filtration, enzymatically hydrolyzed with a cellulase blend (Cellic CTec2), and fermented in mesophilic batch conditions with a microbial consortium derived from pig slurry. The impact on hydrogen yield of initial pH was evaluated by comparing the hydrogen production from hydrolysates with not adjusted (5.3) or adjusted initial pH (8.7) using NaOH or alkaline black liquor. The highest hydrogen yield, 2.0 mol/mol of hexoses, was obtained with alkaline initial pH 8.7, regardless of how the pH adjustment was managed. The yield was 39% higher than that obtained in reactors with initial pH 5.3. In conclusion, thermo-alkaline pre-treatment followed by enzymatic saccharification and initial pH adjustment at 8.7 with the black liquor remaining after pre-treatment is a promising strategy to produce hydrogen from giant reeds in dark fermentation. [ABSTRACT FROM AUTHOR]

In the context of bioenergy production, sorghum and miscanthus are relevant candidates for biogas production. As for many lignocellulosic biomasses, pretreatments can improve the accessibility of carbohydrates for microorganisms during anaerobic digestion. The objectives of this study were (1) to assess environmental impacts of lime and soda pretreatments of both biomasses in co-digestion with manure and (2) to compare the heat produced from natural gas with heat produced from biomethane generated from whole plants of sorghum and miscanthus under different studied scenarios. A comprehensive attributional life cycle analysis (LCA) was performed on 21 sorghum scenarios and 12 miscanthus scenarios. Certain scenarios explored direct and indirect land use change (dLUC and iLUC). An environmental evaluation highlighted that most of the impacts are generated by crop production and by the purification and injection step for both sorghum and miscanthus. Compared to natural gas, the study emphasized that, unlike lime treatment, soda treatment does not provide an added value. Although most impacts are favourable towards natural gas, sorghum-based methane presents very good results (below 0) for six impact categories. The reduction of climate change ranges from − 90 to − 105%. Miscanthus can reduce climate change by − 60 to − 80%, but almost all other impact categories are in favour of natural gas. Lime pretreatment always presents best results. For both sorghum and miscanthus, it is crucial that crops are not cultivated on a land in competition with food production. [ABSTRACT FROM AUTHOR]

Lignocellulosic biomass (LCB) utilization demands pretreatment to disrupt the compact structure and reduce the recalcitrance originating from LCB constituents interaction. Alkaline pretreatment (AP) selectively solubilizes lignin, enhances the accessible surface area, and eventually alters the pretreated residue structure. During pretreatment, heterogeneous susceptibility/recalcitrance of LCB constituents towards pretreatments and various phenomena such as phase transition, de/repolymerization, and lignin solubility are primarily responsible for structure alteration. Lignin structure comprises various kinds of bonds/linkages (β-O-4′, β-β′, and β-5′), and each one might be differently susceptible to a specific pretreatment. Differently susceptible lignin bonds/linkages and the relationship between AP and lignin bond degradation are not fully understood. Sequential alkaline pretreatment (SAP) was applied at constant pretreatment severity to investigate the lignin degradation, structure of residual lignin in the pretreated residue, and the heterogeneous susceptibility/recalcitrance of lignin bonds to categorize the labile/recalcitrant lignin moieties/bonds during SAP. Cellulolytic enzyme lignin (CEL) was isolated from un/pretreated residues and characterized by FTIR, GPC, and 2D NMR (HSQC). Semi-quantification of 2D NMR spectra anticipated the heterogeneous degradation of lignin ether bonds/C-C linkages as β-5′ degraded completely than β-O-4′ and β-β′. It might be due to the accessibility of cellulose/hemicellulose-lignin matrix as each pretreatment step degraded LCB and exposed embedded structure. [Display omitted] • Sequentially alkaline pretreatment (SAP) employed to understand lignin degradation. • Lignin degradation, lignin moieties and bonds susceptibility during SAP studied. • Comparatively, β–O–4′ degraded more with each pretreatment step than β–β′ and β–5′. • β–β′ degraded gradually, and β–5′ became recalcitrant after first pretreatment step. [ABSTRACT FROM AUTHOR]

Alkaline pretreatment (APT) is the promising disintegration pretreatment for the anaerobic digestion (AD) of sewage sludge (SS) to improve digestion efficiency and methane yields. In this study, the heavy metals (HMs) were observed to be leached from SS in the APT process, which could lower the HMs secondary pollution risk of the residual biosolids after AD in land application. The sequential chemical extraction (SCE) experiment was performed to determine the variation in HMs' distribution prior to and after the APT. The alkaline extracts were characterized in order to elucidate the HMs' release mechanism. The APT could cause significant release of Zn and Cu with a maximum release efficiency of 96.6% ± 4.6% and 62.7% ± 8.4% under the condition of 1.5 mol/L NaOH and 25 ℃, respectively. The release efficiency of Zn and Cu was reduced by 63.0% and 21.7%, respectively, due to the extra addition of 0.25 mol/L NaCl at a NaOH concentration of 1.25 mol/L in the APT process. The release of Zn and Cu may be attributed to a complex process including disruption of microbial cells in SS, solubilization of organic matters bounded with metals, and the chemical leaching reaction of minerals. This study demonstrates the possibility to remove the Zn and Cu from the SS in the APT process before the AD disposal. [ABSTRACT FROM AUTHOR]

[Display omitted] Corn stover has been identified as a key resource in the transition from petrochemicals to sustainably sourced energy and materials; however, the as-recovered lignin from alkaline pretreatment contains unusually high levels of residual impurities, which must be removed to maximize potential application. Thus, the Aqueous Lignin Purification using Hot Agents (ALPHA) process was applied to a corn stover lignin containing ∼10 % carbohydrates and ∼3 % ash. Lignin fractions ∼100 times cleaner than the feed lignin and of controlled molecular weight (i.e., as low as one-fifth and as high as triple the absolute molecular weight (Mw) of the feed) were obtained. The ALPHA solvent was a hot (60 or 75 °C) solution of 80 % ethanol combined with the feed lignin at an unusually low, 3:1 solvent-to-feed lignin ratio – conditions that create the liquid–liquid equilibrium (LLE) phase split needed to practice ALPHA. Lignin fractionation then commenced by adding water to the original solution, decreasing the ethanol content in increments of 3–4 wt%. Surprisingly, the highest Mw fractions did not precipitate until the solution contained just below 50 % ethanol, by which point almost half of the starting lignin of near-average Mw had already precipitated. Another unexpected result was that the lignin waste stream from the initial purification step could be increased from 40 to 98 % lignin in a single equilibrium stage simply by re-processing that waste with another 80 % ethanol solution at the conditions given above. In summary, the efficacy of ALPHA for purifying and fractionating an impurities-laden corn stover lignin to ultraclean levels in a scalable manner requiring only aqueous bioethanol solutions has been demonstrated. [ABSTRACT FROM AUTHOR]

Lignin hydrolyzes during alkali-heat pretreatment of lignocellulose, due to the cleavage of covalent linkages between lignin and lignin-carbohydrate complex. Various structure of lignin monomers are responsible of the complicated hydrolysis mechanism of lignin and lignin-carbohydrate complex. This study used density functional theory to reveal the hydrolysis mechanism of lignin with various substituents and lignin-carbohydrates complex with different linkages. The results indicated that the S N 2 reaction was observed to take place in the lignin. Methoxy groups and methyl group had an insignificant influence on hydrolysis reaction pathway of lignin, whereas the presence of a methyl group on the α-carbon atom had a hindering effect on the nucleophilic attack during alkaline pretreatment. The lignin-carbohydrate complex with different linkage showed a significant difference in hydrolysis reaction pathway. Additionally, the reaction energy barrier of ester bond hydrolysis was lowest among the hydrolysis of ester bond, phenyl glycosidic bond, benzyl ether bond, γ-ester bond, coumarin ester bond and acetal bond under alkaline condition. This study provides valuable insights into the process control, reactor design, and performance enhancement for lignocellulose pretreatment. • Mechanism of lignin hydrolysis in alkali thermal pretreatment was studied by DFT. • Mechanism of LCC hydrolysis in alkali thermal pretreatment was studied by DFT. • S N 2 reaction was observed to take place during the lignin hydrolysis. • A methyl group on the α-carbon atom hindered the nucleophilic attack. • Reaction energy barrier of ester bond hydrolysis was lowest during LCC hydrolysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • The NTR of the ISFPD system was 77.3% under initial pH 9. • The PD rates were comparable when subjected to high nitrate concentrations. • High nitrate and pH promoted the release of organics in sludge fermentation. • Macromolecules needed to be hydrolyzed to be available for PD. Achieving partial denitrification (PD) by using fermentation products extracted from waste activated sludge (WAS) rather than commercial organic matters is a promising approach for providing nitrite for anammox, while sludge reduction could also be realized by WAS reutilization. This study proposed an In-situ Sludge Fermentation coupled with Partial Denitrification (ISFPD) system and explored its performance under different conditions, including initial pH, nitrate concentrations, and organic matters. Results showed that nitrite production increased with the elevation of initial pH (from 6 to 9), and the highest nitrate-to-nitrite transformation ratio (NTR) reached 77% at initial pH 9. The PD rates and NTR were observed to be minimally influenced by initial nitrate concentrations. Acetate was preferred by denitrifying bacteria, while macromolecules such as proteins necessitated be hydrolyzed to be suitable for further utilization. The insights gained through this study paved the way for efficient nitrite production and sustainable WAS reutilization in harmony. [ABSTRACT FROM AUTHOR]

Delignification pretreatment with alkali under various conditions (25–160 °C for 1–12 h) or sodium chlorite at 75 °C for 4 h was applied to improve the enzymatic digestibility of sugarcane bagasse by removing hemicellulose and lignin. Compared with the elimination of hemicellulose, delignification contributed more in achieving a higher glucose yield. In addition, the characterization of untreated and pretreated sugarcane bagasse was conducted to determine the influence of hemicellulose and lignin degradation on subsequent enzymatic digestibility. Furthermore, Polysorbate 80 was added to reduce the enzyme loading, shorten the hydrolysis time, and enhance the efficiency of enzymatic hydrolysis, suggesting that the glucose yield of 92.2% was obtained with enzyme loading of 5 FPU/g substrate. However, the increased yield of glucose with Polysorbate 80 occurred with an increased lignin content and a reduction of enzyme loading, and the yield decreased sharply as the hydrolysis time was prolonged from 6 h to 24 h.

To reduce the toxicity of modern feeds polluted by mycotoxins, various sorbents are added to them when feeding animals. A part of the mycotoxins is excreted from the body of animals with these sorbents and remains in the manure. As a result, bulk animal wastes containing mixtures of mycotoxins are formed. It is known that it is partially possible to decrease the initial concentration of mycotoxins in the process of anaerobic digestion (AD) of contaminated methanogenic substrates. The aim of this review was to analyze the recent results in destruction of mycotoxins under the action of enzymes present in cells of anaerobic consortia catalyzing methanogenesis of wastes. The possible improvement of the functioning of the anaerobic artificial consortia during detoxification of mycotoxins in the bird droppings is discussed. Particular attention was paid to the possibility of effective functioning of microbial enzymes that catalyze the detoxification of mycotoxins, both at the stage of preparation of poultry manure for methanogenesis and directly in the anaerobic process itself. The sorbents with mycotoxins which appeared in the poultry wastes composed one of the topics of interest in this review. The preliminary alkaline treatment of poultry excreta before processing in AD was considered from the standpoint of effectively reducing the concentrations of mycotoxins in the waste.

Increasing demand for energy and environmental issues has laid various opportunities for research and development of sustainable, renewable, and environmentally friendly energy. Production of ethanol from biomass has been the focus of researchers due to its feasible characteristics in meeting global energy demands. Moreover, the second-generation ethanol or the ethanol derived from lignocellulosic biomass has been favored due to its diverse biomass resources such as wood, grass, agricultural residue, and municipal waste (newspaper). Hence, Limnocharis flava, an aquatic plant and considered a weed, was investigated and converted into bioethanol. For optimization, the lignocellulosic biomass was examined by various alkaline treatments (0% alkaline, 1% CaO, 2% CaO, and 2% NaOH) to distinguish the suitable pretreatment that can break down lignin, cellulose, and hemicellulose to form sugars that can be fermented to produce bioethanol. Significantly, 1% CaO showed favorable results of ethanol yield of 6.31 ± 0.72 g/L with a total and reducing sugars of 50.81 g/L and 28.88 g/L, respectively. Thus, it can be concluded that bioethanol can be derived from L. flava. [ABSTRACT FROM AUTHOR]

Pennisetum purpureum, commonly known as elephant grass, possesses an immense ability to be recognized as bioenergy crop due to its high carbohydrate content and ample availability in the northeastern states of India. In the present study, an alkaline treatment was conducted using NaOH of different concentrations (1%, 2% and 3% (w/v)) at varying reaction periods of 30, 60 and 90 min with an aspiration of maximum delignification and an enhanced recovery of carbohydrates from biomass. A maximum delignification of 81.0% (w/w) was obtained when the biomass was pretreated with 2% (w/v) of NaOH for 60 min while in the presence of 3% (w/v) of NaOH, the highest cellulose recovery of 72.3% (w/w) was accounted at 90 min of reaction time. During saccharification of biomass, a maximum 18.4 g/L of glucose was produced using 20 filter paper unit of commercial cellulase after 48 h of enzymatic reaction with a cellulose conversion of more than 46%. Furthermore, product inhibition study showed the significant inhibitory effect on enzymatic production of sugars even in the presence of 2 g/L glucose and xylose in the reaction system. The severity of alkaline treatment of the untreated and treated biomass was evaluated using different physiochemical analyses. Moreover, the extracted lignin obtained after acid precipitation of alkaline filtrate was characterised using UV-Visible spectrophotometer. Finally, two-way ANOVA revealed a significant variation in the production of glucose and xylose from biomass even when glucose was added at a fixed concentration (P value = 0.00044 << 0.05) into the reaction system. On the other hand, xylose shows significant inhibition in glucose and xylose production from biomass at both of a particular (P value = 9.05 × 10−7 << 0.05) and different (P value = 0.0078 << 0.05) concentrations of extraneous addition. [ABSTRACT FROM AUTHOR]

Lignocellulosic biomass is an important resource for biofuels, chemicals, and bioproducts; however, deconstructing its recalcitrant structure is a challenge. In this study, controlled instant pressure drop (DIC)-assisted alkaline pretreatment process of poppy capsule waste (PCW) was developed and statistically optimized with the aim of enhanced fractionation efficiency and production of fermentable sugars and xylooligosaccharides (XOs). The effects of DIC process variables on PCW fractionation were investigated. The optimal DIC conditions were found as 5 bar vapor pressure, 540 s processing time, and 9% (w/w) moisture content. At the second stage, optimum conditions for alkaline extraction were found as 22.58% (w/w) KOH, 1-h extraction time, and 22.15 mL precipitant volume. Process optimization concluded a hemicellulose separation yield of 26.37±0.08%, corresponding to 104.7% increase. Process optimization also contributed to the sustainability of the process by reducing KOH and precipitant consumption by 9.7% and 11.4%, respectively, with a concurrent shortening of the processing time from 24 to 1 h. DIC pretreatment enhanced the enzymatic hydrolysis yield of PCW, and a maximum glucan-to-glucose conversion yield of 22.85±0.74% was obtained, which corresponds to a 9-fold increase. Hydrolysis of PCW and hemicellulose-rich fraction by xylanase yielded xylose-free xylobiose (X2) as the principal product. SEM analysis demonstrated the expansion of PCW structure by DIC pretreatment, reasoning the higher fractionation efficiency and enzymatic hydrolysis yields. The optimized process could be an efficient option for lignocellulose fractionation, enzymatic saccharification, and XOs production within biorefinery concept while reducing the requirement for chemicals and processing time. [ABSTRACT FROM AUTHOR]

The present study focuses on the experimental research of the effect of alkaline chemical pretreatment by KOH on biogas production from anaerobic digestion of lagoon station's sludge (dry basis) under mesophilic conditions (35± 2 °C). Different concentrations of KOH, i.e. 1, 2.5, 5 and 7.5% (w/w), were tested for 24 hours at room temperature. The results obtained after two months of digestion, based on the total volume of biogas measured, clearly indicate that the chemical alkaline pretreatment has a positive effect on the anaerobic digestion, since the amount of biogas produced increased by 35.3 % when the concentration of KOH was 5%. Indeed, according to the selected operating conditions, this concentration is considered optimal. Therefore, above this concentration, a blockage and inhibition of the methanogenic activity of the anaerobic digestion process were observed. These results also indicate that the alkaline chemical pretreatment can improve the CH4 content of the biogas obtained. Copyright [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.

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 pH = 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.

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. [ABSTRACT FROM AUTHOR]

An influence of the alkaline pretreatment of wheat straw with use 0.05M solution of NaOH by 22 hours at 25oC temperature on the effectiveness of anaerobic digestion under mesophilic condition were the subject of this study. The water soaked straw were used as a control. The results showed that alkaline pretreatment improved the solubility of the straw biomass, increasing dissolved COD and concentration of VFA in the feedstock of 10% and 21%, respectively, compared to water soaked samples. Consequently, the cumulative biogas yield was enhanced by 21.5%, reaching 412.1 mL g VS-1 for the pretreated biomass. The digestates were similar in terms of TS and VS, but it significantly differed in terms of phenols concentration which content was considerably higher both in the feedstock as also as in digestate containing alkaline pretreated straw. Initial concentration of phenols in the feedstock of 27 mg L-1 did not block the anaerobic digestion, although its inhibiting effect is forecasted. It was concluded that soaking the straw at low loading of NaOH (4% of raw mass (w/w)) under ambient conditions can efficiently improve its usability for biogas production. [ABSTRACT FROM AUTHOR]

Lignocellulosic sugars are the major renewable building blocks for green fuels and chemicals production. However, the implication of an effective pretreatment process is an inevitable process to access the biomass sugars. Alkaline pretreatment is a viable pretreatment process, causing a selective removal of lignin, with a minimum degradation of carbohydrates, increasing porosity and surface area, eventually enhancing enzymatic hydrolysis. Here, we have assessed commercial cloth washing detergents as catalytic agents, for the lignin removal from sugarcane bagasse. Three different detergents (Brilhiante® (B), Omo® (O), Sabonito Flash® (F)) were tested using three different concentrations (5, 10 and 15%) with and without pH adjustment. Pretreatment with O5pH (5% Omo®, pH 12) showed the maximum lignin removal (81.14%) and retainment of cellulose (44.15%), and hemicellulose (29.71%) in the pretreated bagasse. The maximum sugars (26.62 g/L) were released from the O10pH-pretreated sugarcane bagasse. This study shows the potential of washing detergents as the new potential catalytic agents for the pretreatment of biomass for efficient sugars recovery and retaining maximum lignin in the pretreated substrate. [ABSTRACT FROM AUTHOR]

Tobacco product waste (TPW) was considered as a novel and sustainable feedstock for second-generation ethanol production. TPW with over ~ 44% cellulose content was efficiently pretreated using concentrated (10% W/V) sodium hydroxide (SH) solution at different temperatures (0, 25, and 80 °C) and retention times (3 and 6 h). Subsequently, the pretreated biomass was subjected to separate enzymatic hydrolysis and fermentation by the filamentous fungus Mucor hiemalis. Promising results were achieved following 3 h pretreatment of TPW at 80 °C, whereas the hydrolysis yield was substantially increased up to 91.3%. Besides, comprehensive tacking of key features of biomass (e.g., composition, crystalline structure, surface hydrophilicity and morphology, and accessible surface area) by semi-quantitative methods together with FTIR and SEM observations revealed major improvements occurred after mild SH pretreatment. Consequently, the maximum ethanol production as high as ~ 97% of theoretical ethanol yield was obtained, while it was only 44.4% from the untreated TPW. The implication of the work could possibly support TPW utilization for large-scale ethanol production in a tobacco-based biorefinery framework. [ABSTRACT FROM AUTHOR]

Minerals such as quartz, present widely in various volcanic ashes, remain unaltered throughout the low-temperature hydrothermal process currently used in industry to obtain zeolites, causing an incomplete hydrothermal transformation of the starting solid. This study presents a novel and cost-effective procedure which improves the reactivity of ash toward the generation of zeolite by increasing the availability of silica and alumina components. This method leads to a final product with a large zeolite content. The transformation consisted of an ash-activation step followed by hydrothermal zeolitization. The influence of the structural, chemical, and morphological characteristics of the volcanic ash as well as the effect of the activation procedure on the ash reactivity were studied. A collected sample (VA) and an amorphous fraction obtained after VA sieving (VA40, retained on #40 mesh) were used for zeolite production. These solids were alkaline-treated separately, aged, and reacted under controlled conditions of temperature at autogenous pressure. Throughout the process, the solid phases were characterized by X-ray diffraction, energy dispersive X-ray microanalysis, scanning electron microscopy, Fourier-transform infrared spectroscopy, and N2adsorption-desorption porosimetry measurements. After activation and alkaline aging, the presence of quartz and plagioclase minerals in the natural ash seemed to improve the growth of NaAlSiO4 polymorphs, which in turn were transformed easily to zeolite structures. Even under adequate pretreatment and suitable synthesis conditions, the coarse non-crystalline fraction led to low conversion, while the highest conversions to zeolites A and X were obtained from the natural ash. The outcomes of the present study could be used to improve the conversion levels of other non-conventional aluminosiliceous minerals into zeolites. [ABSTRACT FROM AUTHOR]

Non-communicable diseases have a promising link with the glycated proteins and advanced glycation end products, which are formed during hyperglycemic conditions of diabetes mellitus. Consumption of whole grain millets serves as an aid in the management of lifestyle disorders. Despite being the most robust and widely cultivated millet grain and its position as a major food staple, there has been a lack of research on the effects of pearl millet on human health and disease prevention. Therefore, this study was aimed at utilizing pearl millet bran, an agro-industrial waste, to derive feruloylated xylooligosaccharides (FXOS) by enzymatic hydrolysis and examine their potential as a natural antioxidant and antiglycating agent. The isolated FXOS were composed of 25.19 mg/g bound ferulic acid, 227.5 mg/g arabinose, and 359.9 mg/g xylose as the major monosaccharides besides 25.8 mg/g glucose, 27.2 mg/g galactose, and 14 mg/g glucuronic acid with the total arabinoxylan content of 51.5%. FTIR analysis confirmed the presence of backbone having β-glycosidic linkages and bound phenolic group. Further, antiglycation potential was studied with the help of inhibition of fructosamine and protein carbonyl formation and fluorescence measurements. FXOS showed a potent antiglycation effect in the bovine serum albumin (BSA)/glucose model with an inhibition rate of 54.6, 62.8, and 87.7% at 1 mg/mL during the early, middle, and late stages of glycation, respectively. FXOS also inhibited protein aggregation, as confirmed by Thioflavin-T fluorescence measurements and SDS-PAGE. In addition, we evaluated the antioxidant property of FXOS by DPPH, ABTS, FRAP, superoxide radical scavenging, and ferrous ion chelating assays. Our findings suggest that FXOS from pearl millet bran can be utilized as a constituent of functional foods with antiglycation and antioxidant properties. [ABSTRACT FROM AUTHOR]

In the growing search for sustainability, nanocellulose has stood out, since it is obtained from natural fibers, a renewable and biodegradable source, being able to promote the reuse of agricultural waste. Due to their high availability and low cost, residues from pineapple consumption become a viable alternative for the nanocellulose production process, which has not been explored so far. In this sense, the work aimed to produce nanocellulose from pineapple crowns, via acid hydrolysis, promoting the study of different process conditions, to define which methods obtained better results. The fibers were pretreated by mercerizing with sodium hydroxide and bleaching with hydrogen peroxide and sodium hydroxide. This was followed by hydrolysis with sulfuric acid to obtain the nanoparticles. Chemical characterization and scanning electron microscopy were performed on the crude and bleached fibers, and transmission electron microscopy on the produced nanocellulose. The treatments were effective in reducing lignin and hemicellulose in the fiber, and microscopy proved the production of cellulose nanoparticles, with an average width equal to 10.38 nm. Therefore, the results confirmed the potential of the process used to obtain nanocellulose from the pineapple crowns.

Mass production of sustainable biofuels replacing fossil fuels will significantly reduce global greenhouse gas emissions. However, biomass feedstock variability, availability, and affordability pose significant risks for the sustainable production of biofuels in biorefinery plants. To derisk the sustainable production of biofuels, this work investigates the sugar yields and production costs of four different feedstocks as well as their blends, using different pretreatment methods: deacetylation and dilute acid pretreatment (DDA) and deacetylation and mechanical refining pretreatment (DMR). We found that not only feedstock species variability, but also feedstock harvesting techniques have large impacts on both sugar yields and production costs. Single-pass harvested corn stover (SPCS) showed higher sugar yields and lower production costs than multipass harvested corn stover, followed by sorghum and switchgrass. The highest glucose yields of 91% and 95.3%, which corresponds to the lowest sugar production costs of $0.2286/lb. and $0.2490/lb., were observed for SPCS using DDA and DMR, respectively. The difference in sugar yields and production costs due to feedstock variability can be largely mitigated by increasing deacetylation severity, especially in DMR. Higher deacetylation severity resulted in decreased sugar production costs in the case of DMR in contrast to increased costs in the case of DDA. Blending switchgrass and sorghum into corn stover, which can significantly increase the feedstock availability and sustainability, resulted in sugar yields and production costs of roughly the weighted average of those derived from constituent individual feedstocks, respectively. Thus, blending feedstocks of different biomass species is a potential successful strategy for sustainable production of biofuels to replace fossil-derived fuels.

Lignin-carbohydrate complexes (LCCs) in the plant cell wall are responsible for providing resistance against biomass-degrading enzymes produced by microorganisms. Four major types of lignin-carbohydrate bonds are reported in the literature, namely, benzyl ethers, benzyl esters, phenyl glycosides, and acetyl ester linkages. Ester’s linkages in the plant cell wall are labile to alkaline pretreatments, such as ammonia fiber expansion (AFEX), which uses liquid or gaseous ammonia to cleave those linkages in the plant cell wall and reduce biomass recalcitrance. Two competing reactions, notably hydrolysis and ammonolysis, take place during AFEX pretreatment process, producing different aliphatic and aromatic acids, as well as their amide counterparts. AFEX pretreated grasses and agricultural residues are known to increase conversion of biomass to sugars by four- to five-fold when subjected to commercial enzyme hydrolysis, yielding a sustainable feedstock for producing biofuels, biomaterials, and animal feed. Animal feed trials on dairy cows have demonstrated a 27% increase in milk production when compared to a control feedstock. However, the presence of carboxamides in feedstocks could promote neurotoxicity in animals if consumed beyond a certain concentration. Thus, there is the need to overcome regulatory hurdles associated with commercializing AFEX pretreated biomass as animal feed in the United States. This manuscript demonstrates a modified pretreatment for increasing the digestibility of industrial byproducts such as Brewer’s spent grains (BSG) and high-fiber meal (HFM) produced from BSG and dry distillers grains with soluble (DDGS), while avoiding the production of carboxamides. The three industrial byproducts were first treated with calculated amounts of alkali such as NaOH, Ca(OH)2, or KOH followed by AFEX pretreatment. We found that 4% alkali was able to de-esterify BSG and DDGS more efficiently than using 2% alkali at both 10 and 20% solids loading. AFEX pretreatment of de-esterified BSG, HFM, and DDGS produced twofold higher glucan conversion than respective untreated biomass. This new discovery can help overcome potential regulatory issues associated with the presence of carboxamides in ammonia-pretreated animal feeds and is expected to benefit several farmers around the world.

In order to partially mimic the efficient lignocellulose pretreatment process performed naturally in the gut system of Pachnoda marginata larvae, two wheat straw pretreatments were evaluated: a mechanical pretreatment via cutting the straw into two different sizes and an alkaline pretreatment with calcium hydroxide. After pretreatment, gut enrichment cultures on wheat straw at alkaline pH were inoculated and kept at mesophilic conditions over 45 days. The methanogenic community was composed mainly of the Methanomicrobiaceae and Methanosarcinaceae families. The combined pretreatment, size reduction and alkaline pretreatment, was the best condition for methane production. The positive effect of the straw pretreatment was higher in the midgut cultures, increasing the methane production by 192%, while for hindgut cultures the methane production increased only by 149% when compared to non-pretreated straw. Scanning electron microscopy (SEM) showed that the alkaline pretreatment modified the surface of the wheat straw fibers, which promoted biofilm formation and microbial growth. The enrichment cultures derived from larva gut microbiome were able to degrade larger 1 mm alkaline treated and smaller 250 µm but non-pretreated straw at the same efficiency. The combination of mechanical and alkaline pretreatments resulted in increased, yet not superimposed, methane yield.

The sugar palm tree (Arenga pinnata) was abundant in Indonesia and has high cellulose contents for bioethanol production. However, the lignin content was the major drawback which could inhibit saccharification enzymes and therefore removing the lignin from the biomass is important. This paper evaluated the effects of pretreatments using nitric acid (HNO3) and ammonium hydroxide (NH4OH) at 2 to 10% (v/v) on reducing sugar and ethanol contents and compared with the effects of steam pre-treatment. The pretreated samples were hydrolyzed using cellulase enzymes at pH 5.0 with a substrate concentration of 10% (w/v) for 24 to 72 h at 50 °C. Subsequent assessments of enzymatic saccharification following pre-treatment with 10% (v/v) HNO3 showed maximum reducing and total sugar contents in palm tree trunk waste of 5.320% and 5.834%, respectively, after 72 h of saccharification. Following pretreatment with 10% (v/v) of NH4OH, the maximum reducing and total sugar contents of palm tree trunk waste were 2.892% and 3.556%, respectively, after 72 h of saccharification. In comparison, steam pretreatments gave maximum reducing sugar and total sugar contents of 1.140% and 1.315% under the same conditions. Simultaneous saccharification and fermentation (SSF) was conducted at 37 °C (pH 4.8) and 100 rpm for 120 h using 10% (v/v) Saccharomyces cerevisiae and cellulase enzyme with a substrate concentration of 10% (w/v). The result showed the highest ethanol content of 2.648% was achieved by using 10% (v/v) HNO3. The use of 10% (v/v) NH4OH gained a yield of 0.869% ethanol while the steam pretreatment could obtained 0.102% ethanol.

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.

This study investigates the effects of separate and combined chemical (acid and alkaline pretreatment) and torrefaction pretreatment of radiata pine biomass on the pyrolysis kinetic parameters using thermogravimetric analysis (TGA). Thermal degradation profiles of the treated biomass samples were examined and correlated to changes in proximate and ultimate analyses. The TGA results were then used to determine the activation energies (E a) and pre-exponential factors (A) in various kinetic models, including Kissinger, Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO), and simplified Distributed Activation Energy Model (DAEM) methods, where the obtained values of E a for these models ranged between 170.9 and 270.9 kJ mol−1, 170.1–262.3 kJ mol−1, 186.2–259.2 kJ mol−1, and 169.3–266.3 kJ mol−1, respectively, for all of the treated biomass samples. The mean E a values after pretreatments increased in comparison with that of the Control sample. In general, the E a values increased over the degree of conversion from 0.2 to 0.8 attributed to the crystallinity and carbonisation effects upon pretreatments. However, the mean E a values varied with the pretreatment methods, indicating a complex multi-step mechanism of pyrolysis process of the treated biomass. The A values determined for all of the treated biomass samples varied over a broad magnitude ranging from 105 to 1026 s−1 for the adopted kinetic models. [ABSTRACT FROM AUTHOR]

Extremely low-liquid ammonia (ELLA) pretreatment using aqueous ammonia was investigated in order to enhance the enzymatic saccharification of corn stover and subsequent ethanol production. In this study, corn stover was treated with an aqueous ammonia solution at different ammonia loading rates (0.1, 0.2, and 0.3 g NH3/g biomass) and various liquid-to-solid (L/S) ratios (0.55, 1.12, and 2.5). The ELLA pretreatment was conducted at elevated temperatures (90–150 ◦C) for an extended period (24–120 h). Thereafter, the pretreated material was saccharified by enzyme digestion and subjected to simultaneous saccharification and fermentation (SSF) tests. The effects of key parameters on both glucan digestibility and xylan digestibility were analyzed using analysis of variance (ANOVA). Under optimal pretreatment conditions (L/S = 2.5, 0.1 g-NH3/g-biomass, 150 ◦C), 81.2% glucan digestibility and 61.1% xylan digestibility were achieved. The highest ethanol yield achieved on the SSF tests was 85.4%. The ethanol concentration was 14.5 g/L at 96 h (pretreatment conditions: liquid-to-solid ratio (L/S) = 2.5, 0.1 g-NH3/g-biomass, 150 ◦C, 24 h. SSF conditions: microorganism Saccharomyces cerevisiae (D5A), 15 FPU/g-glucan, CTech2, 3% w/v glucan, 37 ◦C, 150 rpm). [ABSTRACT FROM AUTHOR]

Oil palm frond as an abundant and inexpensive lignocellulosic waste was used to optimize alkaline pretreatment for ethanol production. The studied lignocellulosic waste is one of the largest biomasses (47%) in oil palm waste. Oil palm frond fibers were processed by steam explosion, hot water extraction, and alkaline extraction pretreatment, followed by simultaneous saccharification and fermentation (SSF), for ethanol production as an alternative energy resource. To optimize alkaline extraction for oil palm frond, a Taguchi method with a three-factor design constituted a concentration of NaOH (15%, 20%, and 25%), time (30, 60, and 90 min), and temperature (70, 80, and 90 °C). An optimum alkaline extraction condition of 15% NaOH at 90 °C for 60 min gave the highest percentage of α-cellulose (80.74%) and the lowest percentages of lignin (15.99%), ash (1.05%), and pentosan (2.09%). In addition, the optimized pretreatment condition significantly improved α-cellulose to 52.65% and removed lignin up to 51.78%. Simultaneous saccharification and fermentation (SSF) was carried out with 10% (dry weight) alkaline pretreated OPF fibers, Celluclast 1.5 L (15 FU/gram substrate), Novozyme 188 (15 IU/gram substrate), and Saccharomyces cerevisiae SC90 at 40 and 45 °C. The highest ethanol concentration, theoretical ethanol yield, and ethanol productivity observed at 40 °C were 33.15 g/L, 72.54%, and 0.55 g/L/h, respectively. The results suggest that an optimized alkaline pretreatment process using palm frond as a lignocellulosic waste is a sustainable approach to produce efficient ethanol production.

Alkaline pretreatment and sequential enzymatic hydrolysis of soybean hull were investigated to obtain fermentable sugars for polyhydroxyalkanoates production along with residual glycerol as low-cost carbon sources. Soybean hull is composed of approximately 32% cellulose, 12% hemicellulose, 6% lignin, and 11% protein. Alkaline pretreatment was carried out with 2% NaOH concentration, 10% (w/v) biomass loading, and 60 min incubation time in an autoclave at 120 °C. The response surface methodology (RSM) based on the central composite design (CCD) tool was employed to optimize the enzymatic hydrolysis process, where the variables of biomass loading, enzymes’ concentration, and time were considered. The maximum total reducing sugars concentration obtained was 115.9 g∙L−1 with an enzyme concentration of 11.5 mg protein/g dry substrate for enzyme preparation B1, 2.88 mg protein/g dry substrate for XylA, and 57.6 U/g dry substrate for β-glucosidase, after 42 h at 45 °C, and pH was 4.5. Subsequently, the saccharification step was conducted by increasing the processing scale, using a 1 L tank with stirring with a controlled temperature. Implementing the same enzyme concentrations at pH 4.5, temperature of 45 °C, 260 mL working volume, and incubation time of 42 h, under fed-batch operation with substrate feeding after 14 h and 22 h, a hydrolysate with a concentration of 185.7 g∙L−1 was obtained. Initially, to verify the influence of different carbon sources on Cupriavidus necator DSMz 545 in biomass production, batch fermentations were developed, testing laboratory-grade glucose, soybean hull hydrolysate, and waste glycerol (a by-product of biodiesel processing available in large quantities) as carbon sources in one-factor-at-a-time assays, and the mixture of soybean hull hydrolysate and waste glycerol. Then, the hydrolysate and waste glycerol were consumed by C. necator, producing 12.1 g∙L−1 of biomass and achieving 39% of polyhydroxyalkanoate (PHB) accumulation. To the best of our knowledge, this is the first time that soybean hull hydrolysate has been used as a carbon source to produce polyhydroxyalkanoates, and the results suggest that this agro-industrial by-product is a viable alternative feedstock to produce value-added components.

Hazelnut shells, a high lignin containing biomass, were subjected to individual and sequential liquid hot water (LHW), alkaline (AP) and dilute acid pretreatments (DAP). Among the single pretreatments, LHW demonstrated the highest cellulose recovery of 98.1%, DAP resulted in the highest hemicellulose solubilization of 56.0%, and AP of the highest lignin removal of 49.6%. Employing two-step pretreatment on hazelnut shells, in general, demonstrated an enhanced action of the second pretreatment; therefore, the sequence of the pretreatment methods had a significant impact on both substrate characteristics and enzymatic hydrolysis efficiency of biomass. In terms of delignification, AP-LHW achieved 60.7% lignin removal, while LHW-DAP showed the highest hemicellulose removal of 93.8% and DAP-LHW resulted in the highest cellulose recovery of 94.0%. Structural properties of raw and pretreated hazelnut shells were observed by FTIR. The maximum glucose recovery of 54.9% was observed in DAP-LHW pretreated samples. For this pretreatment combination, almost 1.8 MJ total energy was required to recover 10.2 g glucose. The findings indicated that complete removal of the physical barrier of lignin and hemicellulose might not be essential; partial relocation of lignin and alteration of cellulose structure may also be efficient in increasing the sugar recovery from the lignocellulosic biomass. [ABSTRACT FROM AUTHOR]

Mature coconut husk (MCH) and young coconut husk (YCH) are abundantly generated as a by-product from coconut-based industry, which eventually lead to environmental pollution. However, the lignocellulose content in both types of coconut husk has the potential to be exploited as feedstock by way of biochemical processes through the concept of biorefinery. In this study, the MCH and YCH were subjected to alkaline pretreatment by sodium hydroxide (NaOH). Subsequently, enzymatic hydrolysis using Accellerase® 1500 was conducted to convert the lignocellulosic materials into fermentable sugars. The changes in surface morphology of MCH and YCH throughout the process were also observed. Alkaline pretreatment successfully removed 20.15 and 31.17% of lignin content in MCH and YCH, respectively. The increase in cellulose content after alkaline pretreatment was detected around 17% for MCH and 20% for YCH. For optimisation of enzymatic hydrolysis, 10% enzyme loading for 24 h showed significantly higher (p < 0.05) reducing sugar content in MCH and YCH hydrolysates of 19.17 g/L and 24.33 g/L, respectively. The efficiency of the hydrolysis process was proven by high sugar recovery of 71.23% for MCH and 89.49% for YCH. Concurrently, the morphological analysis showed the effect of the treatments on the surface of MCH and YCH, where the structure became swollen and collapsed as the majority of lignocellulosic materials were digested. Therefore, the study pointed out the potential of reutilising MCH and YCH as alternative resources for the future biochemical process feedstock. [ABSTRACT FROM AUTHOR]

Beyond the conventional consideration of pretreatment severity (PS) responsible for biomass disruption, the influence of reagent properties on biomass (LCB) disruption is often overlooked. To investigate the LCB disruption as a function of reagent properties, reagents with distinct cations (NaOH and KOH) and significantly higher delignification potential were chosen. NaOH solution (3 % w/v) with a measured pH of 13.05 ± 0.01 is considered the reference, against which a KOH solution (pH = 13.05 ± 0.01) was prepared for LCB pretreatment under the same PS. Despite comparable lignin content, varying glucose yield of NaOH (68.76 %) and KOH (46.88 %) pretreated residues indicated the presence of heterogeneously disrupted substrate. Holocellulose extracted from raw poplar (ASC, control) and alkaline pretreated residues (C-NaOH and C-KOH) were analyzed using HPLC, XRD, SEM, TGA/DTG, XPS, and 13CP MAS NMR to investigate the pretreatment-induced structural modification. Results revealed that, despite the same pretreatment severity, better disruption in C-NaOH (higher accessible fibril surface and less-ordered region) leading to higher digestibility than C-KOH, likely due to the smaller ionic radius of Na+, facilitates better penetration into dense LCB matrix. This study elucidates the importance of considering the reagent properties during LCB pretreatment, eventually enhancing consciousness while selecting reagents for efficient LCB utilization. [Display omitted] • Emphasized considering the inherent properties of reagents for biomass pretreatment • Different reagents disrupted biomass heterogeneously under the same pretreatment severity (PS) • Under the same PS, NaOH transformed substrate in favor of enzymatic hydrolysis than KOH • The small ionic radius of Na+ facilitated penetration into the biomass matrix • Extracted holocellulose from NaOH-pretreated residue exhibited more amorphous region than KOH [ABSTRACT FROM AUTHOR]

• Increasing textile waste generation has risen European Union to implement regulations and strategies. • Chemo-enzymatic treatment of blended textiles enabled selective hydrolysis and removal of cellulose allowing polyester recovery. • Precise condition adjustment is crucial to avoid polyester damage and ensure complete cellulose removal. • Optimized conditions can transform the textile industry from linear to circular, reducing the amount of textile waste. • Industrial implementation realises a sustainable textile biorefinery concept. The study demonstrates the potential of enzymatic hydrolysis and alkaline pretreatment for sustainable blended textile recycling. The target is complete cellulose removal while preserving the polyester integrity for recovery. Interactions of sodium hydroxide concentration (10 %–30 %), urea concentration (0 %–12 %), and temperature (-20 °C–50 °C) were investigated during pretreatment using a design of experiments. Analysis revealed a bimodal pattern in polyester mass loss, with one peak at lower concentrations and temperatures, and a more prominent peak at higher concentrations and temperatures. Cellulose hydrolysis also occurred under high NaOH concentrations and elevated temperatures (50 °C, 30 % NaOH, 0 % urea). Optimal conditions, preserving polyester integrity while achieving complete cellulose elimination, were identified at temperatures between 6.2 °C and 13.3 °C, with NaOH concentrations of 20.7 %–26.6 % (0 % urea) or 13.9 % NaOH and 12 % urea. These findings pave the way for a greener, more efficient textile recycling, advancing the circularity for textiles. [Display omitted] [ABSTRACT FROM AUTHOR]

The biomass of agricultural wastes as a source of fermentable sugars for biofuels production will address the food security and environmental preservation issues. These wastes are rich in lignocellulosic materials which can be hydrolyzed into fermentable sugars. However, low sugar yield and high energy consumption are some of the challenges faced in the process of hydrolization. This study investigated the low-cost corncob substrate for glucose production by dilute sulphuric acid hydrolysis in the presence of ZnCl2 at temperatures below 100°C after pretreatment with 10% NaOH.Time dependent hydrolysis data were analyzed by Saeman model, and thermodynamic parameters were obtained using Erying and Arrhenius equations while Box-Behnken model (Design Expert 6.0 version) was used for experimental design. As the substrate concentration increased from 50 mg/L to 150 mg/L, glucose yield increased from 10.4 mg/g to 14.6 mg/g for pretreated corncob while an increase from 3.4 mg/g to 8.6 mg/g was noted for untreated corncob. The hydrolysis rate constant was two orders of magnitude higher than the degradation rate constant. Thermodynamic parameters revealed endothermic process with positive Gibb’s free energy of hydrolysis having average values of 84.76 kJ/mol and 79.87 kJ/mol for pretreated and untreated samples respectively. The optimum yield from the model was found to be 177.44 mg/g with 3.94% H2SO4 and 0.43 mol/L ZnCl2 for 200 g/L compared with optimum yield of 46.37 mg/g obtainable without ZnCl2. The results of this study showed that the alkaline pretreatment of corncob increased the accessibility of cellulose from the solid fraction and increased glucose production.

The perennial rhizomatous grass giant reed (Arundo donax L.) can be exploited to produce hydrogen by dark fermentation. This implies a high availability of simple sugars, like glucose and xylose, and, thus, a pre-treatment is necessary to remove lignin and expose the holocellulose to enzymatic attack. This study aimed at evaluating the hydrogen production from giant reed hydrolysates. Giant reed dry meal was pre-treated with diluted NaOH (1.2% weight/weight), then the solid fraction was separated from the alkaline black liquor by filtration, enzymatically hydrolyzed with a cellulase blend (Cellic CTec2), and fermented in mesophilic batch conditions with a microbial consortium derived from pig slurry. The impact on hydrogen yield of initial pH was evaluated by comparing the hydrogen production from hydrolysates with not adjusted (5.3) or adjusted initial pH (8.7) using NaOH or alkaline black liquor. The highest hydrogen yield, 2.0 mol/mol of hexoses, was obtained with alkaline initial pH 8.7, regardless of how the pH adjustment was managed. The yield was 39% higher than that obtained in reactors with initial pH 5.3. In conclusion, thermo-alkaline pre-treatment followed by enzymatic saccharification and initial pH adjustment at 8.7 with the black liquor remaining after pre-treatment is a promising strategy to produce hydrogen from giant reeds in dark fermentation.

Summary: The objective of this study is to explore the feasibility of sequential hydrothermal and alkaline pretreatment in improving enzymatic hydrolysis and sugar production of coconut pulp residue for bioethanol production. Hydrothermal pretreatment with the different heating duration of 20, 40, 60 minutes yielded 32.27, 27.51, and 26.72 g/L of total sugar, respectively. After posttreatment with 1%, 2%, and 3% alkaline treatment, the further increment of almost 90% on sugar production was observed. Compared to the single pretreatment, the combination of hydrothermal and alkaline pretreatment significantly affected the enzymatic hydrolysis. The optimum condition for efficient hydrolysis was 40 minutes hydrothermal pretreatment, followed by 1% NaOH posttreatment. At these conditions, the total and reducing sugar was 257.14 ± 0.92 and 102.86 ± 0.82 g/L and the maximum ethanol achieved was 27.19 g/L on the 48 hours of fermentation with efficiency and ethanol productivity of 51.83% and 0.57 g/L/h, respectively. [ABSTRACT FROM AUTHOR]

In this study, the effect of thermo‐alkaline pretreatment and recycling of the liquid fraction (black liquor) for successive pretreatment steps on chemical composition and methane yields from horse manure was investigated. At first, horse manure was subjected to alkaline pretreatment at 70 °C for 1 h (8.6 g NaOH/100 g total solids). Pretreated biomass was then separated into solid and liquid fractions (black liquor). In the subsequent stages, black liquor was mixed with 20% (v/v) of fresh NaOH and was reused to pretreat subsequent batches of horse manure (cycles 1–4). Chemical analyses showed that thermo‐alkaline pretreatment was effective in the delignification and solubilization of organic matter and thereby increased the holocellulose (cellulose and hemicelluloses) content in the solid fraction of horse manure. On comparison with untreated horse manure methane yields (225 ± 1 L CH4 kg−1 VSadded), thermo‐alkaline pretreatment improved the methane yields of horse manure by 39% (313 ± 16 L CH4 kg−1 VSadded). However, the effectiveness of black liquor recycling on methane production decreased (from 39 to 12%) with an increase in the number of recycling steps (from 1 to 4). Nevertheless, recycling of black liquor reduced the consumption of NaOH (40%) and water use (60%). Thus, thermo‐alkaline pretreatment with liquor recycling was found to be an effective pretreatment with an economic gain of 2.4 to 10.4 compared to pretreatment without recycling. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

Anaerobic digestion (AD) of walnut shells (WS) results in only a limited biomethane yield because of their high fibre content, which ultimately represents an essentially nonbiodegradable lignocellulosic biomass. In the present study, thermal (i.e. 50–250 °C), alkaline (i.e. 1–5% w/w NaOH) and combined alkaline-thermal (i.e. 4% w/w NaOH + 150 °C thermal) pretreatment methods have been applied to increase the anaerobic biodegradation of WS. The highest biomethane yields of 159.9 ± 6.8 mL CH4.g VS–1 and 169.8 ± 6.8 mL CH4.g VS-1 were achieved after pretreatment at both 250 °C and with 4% NaOH. After combined NaOH-thermal pretreatments, the AD process showed the largest total VFA concentration (i.e. 1280.1 mg Hac L–1) but a relatively high lag phase (i.e. 3.90 days) compared to thermal and NaOH pretreatments alone, from which the highest biomethane yield (i.e. 192.4 ± 8.2 mL CH4.g VS-1) was achieved at the end of the AD process. The highest biomethane yield from the combined NaOH-thermal pretreated WS was corroborated by the corresponding highest SCOD/TCOD ratio (i.e. 0.37 ± 0.02) and the highest lignocellulosic fibre removal (i.e. 41.1 ± 2.7% cellulose, 35.6 ± 1.8% hemicellulose, and 58.7 ± 3.2% lignin). The cumulative biomethane yields were further simulated via a modified Gompertz model. This study provides a promising strategy in the sense that the biomethane yield of WS containing large amounts of lignin can be significantly increased via thermal, NaOH, and combined NaOH-thermal pretreatment methods. [ABSTRACT FROM AUTHOR]

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]