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Despite the high demand for curdlan (Curd), its industrial implementation has not reached a mature stage due to the high cost of simple sugar feed stocks. Herein, Musa sapientum peels hydrolysate (MPH) was proposed for the first time as a sustainable medium for Curd generation and as an ameliorated functional biomaterial for quercetin (Quer) sustained release. In this study, banana peels have been hydrolysed by 3 % NaOH catalyst/ 60 °C, yielding high concentration of glucose 20.5 ± 0.04 and 24.3 ± 0.11 g/L and reducing sugar amount, respectively. Meanwhile, a novel local Rahnella variigena ICRI91 strain was isolated from soil, that was useful for Curd production and identified by 16S rRNA analysis. Furthermore, three-batch fermentation models were carried out using MPH for obtaining a sufficient yield of Curd. R. variigena ICRI91 accumulated a satisfactory Curd concentration; 10.3 ± 0.25 g/L; using 60 g/L MPH. On the other hand, the strain produced an impressive Curd yield; 21.5 ± 0.13 g/L with an attained productivity of 0.179 ± 0.01 g/L/h and a sugar consumption of 68 ± 0.25 % as the MPH content increased to 100 g/L. For the first time, Curd hydrogel was modified by different amount of Xylitol (Xyl), reaching good mechanical performance; 3.1 MPa and 75 % for tensile strength (TS) and elongation at break (EB), respectively. Curd/Xyl (3/5) hydrogel was then integrated with nanometer-sized quercetin nanocrystals (Quer NCs, 83 ± 0.12 nm) with high colloidal stability of −23 ± 0.05 mV. The interconnected H- bonding between Xyl and Curd was confirmed by FTIR and SEM. The generated biomaterial was tailored to exhibit a sustained Quer release over 72 h. It also has improved antibacterial efficacy against four bacterial pathogens compared to that of a free drug. In recognition of these merits, an edible polymeric nanomaterial has been proposed for the functional food and biomedicine sectors. [Display omitted] • Banana peels hydrolysate saccharification represents a sustainable feedstock for curdlan production. • New Rahnella variigena ICRI91 produced a satisfactory 21.5 g/L curdlan using 100 g/L peels hydrolysate. • Xylitol strengthened the curdlan edible gel network by increasing H- bondings. • Curd/Xyl/Quer NCs gel had promising mechanical properties compared to native curdlan. • Hydrogel exhibited a sustained release of Quercetin NCs and potent antibacterial efficacy. [ABSTRACT FROM AUTHOR]

Lignocellulosic biorefinery faces challenges associated with high energy input during pretreatment and high enzyme cost for enzymatic hydrolysis of cellulose, as well as the intricate valorization of lignin and hemicellulose. This study applied KOH-urea pretreatment to obtain maximum lignin removal of 68.93 % from rice straw at 80 °C for 60 min. The pretreatment consumed only 10.49 % of the total energy input. Five-time dilution of neutral black liquor can optimally stimulate the plant growth. Enzymatic conversion of KOH-urea-treated rice straw attained 92.02 % at 20 % solid concentration with 10 FPU cellulase/g substrate. The ethanol concentration achieved 37.02 g/L at a yield of 75.89 %. The solid residue after fermentation contained 42.40 % dietary fiber and 16.70 % protein, which is suitable as animal feed. This study developed a simple bio-circular way to concurrently produce liquid fertilizer, bioethanol, and animal feed from rice straw. [Display omitted] • KOH-urea pretreatment shared only 10.49 % of total energy consumption. • Enzymatic conversion of rice straw reached 92.02 % at 20 % solid concentration. • Black liquor can be prepared as fertilizer after pH adjustment and proper dilution. • Solid residues after fermentation are suitable as animal feed. • A feasible bio-circular way of lignocellulosic biorefinery is constructed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Alkali, thermal and combined treatments prior to digestion affect PET MPs' quality. • Alkali-thermal combined pretreatment improves methane production from sludge by 22%. • PET MPs improve methane production in anaerobic digestion at 3 mg MP/g TS sludge. • Sludge pretreatment overwhelms the effect of PET MPs on methane generation. • Microbial action and physicochemical treatment affect PET structure differently. Plastics are resilient, hard to degrade materials that can persist in nature for centuries. Microplastics (MPs) exhibit similar tough character and hold the potential to harm marine and terrestrial ecosystems upon their release into the environment. Most modern wastewater treatment plants remove MPs from wastewater with over 90% efficiency but unfortunately concentrate them in sludge. Recent studies have reported MPs' impact on the performance of sludge treatment systems, including anaerobic digesters. Despite its resilience, polyethylene terephthalate (PET) has inherent weaknesses against alkaline and thermal conditions and becomes more prone to further degradation if exposed to such stress conditions. Sludge pretreatment practices aiming to increase biogas production by disrupting floc structure show great similarity with the stress factors mentioned. Thus, this study aims to integrate pretreatment with anaerobic digestion and investigate the fate and effects of PET MPs during these processes. For this purpose, waste activated sludge samples spiked with different doses of PET (0, 1, 3, 6 mg/g TS) in sizes of 250–500 µm were pretreated by 0.5 M alkali for two days and then thermally hydrolyzed at 127 °C for 120 min. Pretreated and unpretreated sludges were digested in a 60-day biochemical methane potential test. The results showed that the spiking of PET MPs into sludge posed a positive impact on the methane yield of unpretreated reactors at statistically significant levels. Integrating pretreatment increased the methane yield by 22.0% and made the impact of MPs on digester efficiency no longer observable. Also, PET exposed to pretreatment and 60-day digestion experienced remarkable changes in surface morphology, crystallinity and carbonyl index, which can further impact their fate and effects on the environment. [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]

This research aims to assess the effect of alkaline pretreatments on the antioxidant potential of β-carotene-rich extracts from the microalga Dunaliella salina and the cumulative biomethane production from its spent biomass, within the framework of a circular economy approach using four biorefineries. A solvent screening was performed, with ethyl acetate achieving the maximum β-carotene extraction yield (5.3% ± 0.03%). Alkaline pretreatments were applied to the initial biomass (direct) and extracts after a extraction with ethyl acetate (indirect), using two matrices: water (W) and a mixture water:ethanol (WE). Direct alkaline pretreatments (D) offered extracts with higher potential than indirect pretreatments (I) in terms of: i) antioxidant capacity, as measured by ABTS•+ assay (0.69±0.1 and 0.61±0.1 mmolTE/gDW for W-D and WE-D, respectively, and 0.55±0.1 and 0.53±0.1 mmolTE/gDW for W-I and WE-I, respectively) and •OH scavenging activity (1.89±0.2 and 2.05±0.5 mmolTE/gDW for W-D and WE-D, respectively, and 0.48±0 and 1.2±0.3 mmolTE/gDW for W-I and WE-I, respectively), ii) biomethane production from their spent biomass (301±14 mLCH 4 /gVS and 289±9.0 mLCH 4 /gVS for W-D and WE-D, respectively, compared to 235±57 mLCH 4 /gVS without alkaline pretreatment), and iii) sustainability analysis, which includes the assessment of the biomass exploitation for β-carotene extraction and biomethane production. The most sustainable biorefinery was W-D as it achieved the highest biomass exploitation (33.8%), compared to WE-D (29.1%), W-I (33.1%) or WE-I (32.8%). This underscores the novelty and effectiveness of direct alkaline pretreatments for enhancing both antioxidant potential and energy recovery from D. salina biomass in a biorefinery context. [Display omitted] • Establishing a sustainable strategy to harness the full potential of D. salina. • Alkaline direct treatment of D. salina in aqueous media is the most effective option. • Enhanced antioxidant properties of β-carotene extracts and biomethane production. • Efficient biomass exploitation for both β-carotene extraction and methane production. [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]

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]

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]

[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]

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]

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]

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]

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]

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]

Graphical abstract Highlights • Fractionation of sugarcane bagasse under mild alkaline conditions. • Identification of five main pools of molecules in the alkaline extract. • Purification by chromatography on strong acid cation resins with water as eluent. • Separation of sugar oligomers and lignin oligomers from the other molecules. • Separation of phenolic monomers from each other according to their structure. Abstract Sugarcane bagasse (SCB) was treated under mild alkaline conditions (solid:liquid ratio of 1:20 (w/v), 1.5% NaOH (w/v), 60 °C, 6 h) to fractionate the lignocellulose in order to produce a typical mild alkaline extract from a lignocellulosic biomass. The solid residue was enriched in cellulose, while the SCB alkaline extract contained lignin and hemicelluloses, but also inorganic salts, five phenolic monomers and acetic acid. After concentration of the alkaline extract by evaporation, low pressure chromatography with water as eluent was performed to produce purified fractions. Two different strong acid cation (SAC) exchange resins were tested: one gel-type resin and one macroporous-type resin. The lignin and hemicelluloses were separated from the inorganic salts by the gel-type SAC exchange resin. On this resin, the phenolic monomers were partitioned regarding the presence or absence in their structure of a carboxyl group. On the macroporous-type SAC exchange resin, the largest sugar oligomers and lignin oligomers were obtained in a fraction free of inorganic salts, phenolic monomers and acetic acid. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cyanide leaching of a Ag-containing polymetallic sulfide is inefficient (40% extraction) • An alkaline pretreatment increases the efficiency of cyanide leaching (80% extraction) • XRD and XPS allow, respectively, for analysis of bulk and surface layers. • Pretreatment removes elemental sulfur and exposes clean sulfide layers. • Other elements such as Fe, Mn, Pb, As and Sb do not seem to affect leaching efficiency. Polymetallic sulfide ores are often not amenable to cyanide leaching due to the presence of several elements and minerals capable of interfering with this process. Thus, various strategies, such as chemical pretreatments, are often studied to improve the efficiency of cyanidation. Beyond the results of such strategies, it is important to understand the changes occurring on the mineral samples during these pretreatments. Herein, an alkaline pretreatment was applied to a silver concentrate (∼8 kg Ag/t) composed of polymetallic sulfides (Fe-Pb-Mn), which increased the silver extraction during subsequent cyanidation from 40% to 80% and decreased the cyanide consumption in half (from approximately 60 to 30 kg NaCN/t). X-ray diffraction (XRD) and ICP-MS indicated that the pretreatment could remove significant amounts of elemental sulfur, which is a known cyanicidal agent. The dissolution of significant amounts of sulfur was confirmed by chemical analysis, which also demonstrated that the dissolution of iron, lead, manganese, and silver were negligible during pretreatment. At surface level, X-ray photoelectron spectroscopy (XPS) demonstrated that the pretreatment exposes fresh sulfide surfaces (e. g. pyrite). In addition, the XPS spectra indicated that the pretreatment facilitated the exposure of clean mineral surfaces. The presence of cleaner surfaces suggested a more uniform and less hindered diffusion of leaching agents through the mineral. Indeed, fitting the extraction data to the shrinking core model showed that pretreated samples featured a nearly ideal diffusion-controlled process, while in the case of untreated samples this fitting was less adequate. During cyanidation of both untreated and pretreated samples, lead build-up was detected on the surface (readsorption), which suggested that this phenomenon does not affect the efficiency of a leaching process. This study highlights the importance of combining bulk analytical methods with surface-sensitive techniques to obtain a more complete understanding of leaching processes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Alkaline pretreatment of LCB was essential to achieve open one-pot production of PHB. • Open one-pot fermentation significantly promoted enzymatic hydrolysis of LCB. • Multi-objective optimization maximized the value of one-pot production of PHB. • Developed an open dual one-pot fermentation for whole LCB components conversion. • The open dual one-pot-fed-batch fermentation produced 20.88 g/L of PHB. The high cost associated with polyhydroxybutyrate (PHB) production demands immediate attention to advance its commercial viability. Herein, we innovatively construct highly efficient production of PHB from low-cost lignocellulosic biomass (LCB) using an open one-pot fermentation by the alkali-halophilic Halomonas alkalicola M2 developed in our previous work. We first develop alkaline pretreatment of LCB to achieve open one-pot fermentation and efficient conversion. Multi-objective optimization of fermentation conditions produces 103.421 mg/L of PHB with a content of 14.437 % and effectively promotes saccharification with cellulose and xylan enzymatic efficiencies of 82.948 % and 73.710 %, respectively. We then develop an open dual one-pot fermentation process, involving the conversion of lignin- and lignin-derived compounds-enriched slurry in the first pot and subsequent polysaccharide conversion in the second pot, to achieve efficient whole LCB components conversion, yielding a record 9.57 g/L of PHB. More importantly, we extend an open dual one-pot-fed-batch fermentation, producing 0.80 g/L of PHB with 27.69 % content in the first pot and 20.08 g/L of PHB with 61.86 % content in the second pot, showing significantly higher than many reported strains. Overall, this work demonstrates the effectiveness of utilizing cheap LCB in a newly designed fermentation process to produce PHB efficiently, representing a significant advancement in this field. [ABSTRACT FROM AUTHOR]

Highlights • Rice husk (RH) varieties in Uganda were characterized, and alkaline pretreated. • Char yield from the pyrolysis of RH varieties ranged from 32–47%db. • NaOH-pretreatment (2–4%w/v) reduced the ash content of RH varieties by 74–93%. • NaOH-pretreatment enhanced RHs' surface area, volatile matter and carbon contents. • Properties varied among RH varieties, suiting them for different applications. Abstract In this study, 13 rice husk (RH) varieties from 4 agro-ecological zones in Uganda were characterized, NaOH-pretreated, and evaluated for their potential utilization as precursors for production of bio-oil, ash, char, and activated carbon for selected applications. RH varieties were characterized through particle size analysis, bulk density, proximate and ultimate analyses, specific surface area, pore volume, as well as lignocellulosic and inorganic compositions. Selected RH varieties were subsequently pretreated at NaOH concentrations of 1–4%w/v, using pretreatment ratios of 5 g RH: 40 mL NaOH. Properties varied among RH varieties, suiting them as feedstocks for different applications. Upland rice husk varieties are more suited precursors for production of bio-oil, and activated carbon due to their relatively lower ash content, higher specific surface area, as well as higher volatile matter and fixed carbon contents. Upland rice husks could as well be employed in the preparation of electrodes for electrochemical devices, due to their relatively higher specific surface area. A high ash content (21–32% dry basis) of lowland rice husks presents good prospects for their calcination, since larger amounts of rice husk ash could be obtained, and employed in different applications. Lowland rice husk varieties could also be more suited precursors for production of char for soil amendment, due to their relatively higher ash content, which subsequently increases their char yields. However, alkaline pretreatment of rice husks using 2–4%w/v NaOH can reduce the ash content by as much as 74–93%, depending on the rice husk variety, which paves way for utilizing rice husks with a high ash content in different applications. Aside from ash reduction, the enhanced specific surface area (1.2–1.7 m2 g−1), volatile matter (68–79%db) and fixed carbon (19–24%db) contents of NaOH-pretreated rice husks suggests they are more suited feedstocks than when employed in their raw form, for production of bio-oil, as well as activated carbon. [ABSTRACT FROM AUTHOR]

Lignin can negatively impose on the enzymatic hydrolysis of pretreated lignocellulose through non-productive enzyme adsorption and/or steric hindrance. The effect of the residual lignin on enzymatic hydrolysis was evaluated with sugarcane bagasse (SCB) samples containing different lignin contents and their milled and enzymolytic lignins (MELs) retaining the intact protolignins. The results showed that the improvement of enzymatic hydrolysis of SCB would become insignificant when the lignin removal achieved above 64.0%, and the changes in chemical groups of lignin had slight impact on adsorbing enzymes. When the lignin retention in the pretreated SCB was less than 36.0%, the residual lignin would not significantly influence the enzymatic hydrolysis via enzyme adsorption and steric hindrance. The contributions of the residual lignins in pretreated SCB samples to the total enzyme adsorptions of pretreated SCB samples were only in the range of 9.6% to 15.5%, which were not predominant for the total enzyme adsorptions. [ABSTRACT FROM AUTHOR]

In this study, organosolv pre-extraction of wheat straw (WS) was conducted to extract lignin for understanding the effect of silica on enzymatic hydrolysis of carbohydrates. The results showed that the presence of silica in the WS substrate was associated with a decreased conversion of carbohydrates into monomeric sugars during enzymatic hydrolysis. Then, a sequential two-stage pretreatment process comprising ethanol pre-extraction and alkaline pretreatment was investigated to convert WS carbohydrates into bioethanol and recover lignin and silica. The results demonstrated that the pre-extraction with ethanol at 160 °C for 50 min followed by alkaline treatment with 11% sodium carbonate (Na 2 CO 3 ) was sufficient to generate a highly digestible substrate. 85.7% of the original sugars in the raw feedstock was recovered by two-stage pretreatment followed by enzymatic hydrolysis with an enzyme loading of 12 FPU/g glucan. Fermentation with Saccharomyces cerevisiae SR8 u strain consumed 97.8% sugars in the hydrolysate to reach 6.5% w/v ethanol titer. With this proposed process, about 89.1% silica and 62.5% lignin were recovered at high levels of purity. [ABSTRACT FROM AUTHOR]

Material balance and preliminary technical analyses of pilot scale sugarcane bagasse alkaline pretreatment, using sodium hydroxide with and without anthraquinone (AQ) addition were analyzed and compared to elucidate the carbohydrates and phenolic components flux in the streams. The lowest carbohydrates solubilization rates (9% wt for cellulose and 41% wt for hemicelluloses) were reached for the condition at 130 °C with AQ addition, however the highest lignin solubilization (87% wt) was accomplished for the condition using 170 °C with AQ addition. Preliminary technical analysis was carried out to evaluate the performance of the best pretreatment condition when integrated to a first and second generation ethanol plant, in a biorefinery concept, showing that 83.03 m 3 /h of ethanol can be produced by this process. Ethanol production (in L/ton biomass) for proposed process is 8.1% lower than the expected for short terms technologies concluding that upgrades on the process, as higher solids concentrations and lignin energy use or, principally, lignin valorization must be performed to allow viability of the process. [ABSTRACT FROM AUTHOR]

Abstract The concentration range of sodium hydroxide solution (0.0–7.0% w/w) was used to determine the impact of chemical pretreatment in bioethanol production from Japanese bamboo by using the white rot fungus Phlebia sp. MG-60. A pretreatment of sodium hydroxide at 120 °C for 1 h demonstrated a significant effect on the removal of lignin and xylan components, leading to an increase in glucan composition for the pretreated bamboo. The saccharification rate was improved from 41.0% in the initial sample to 89.5% in the 7.0% NaOH pretreated sample. This first report on consolidated bioprocessing of Japanese bamboo points out that the highest ethanol yield was 12.8% in 7.0% NaOH pretreated samples, equivalent to 28.5% of polysaccharide volume converted to ethanol, while the conversion proportion in the initial bamboo sample was negligible. Bioethanol production by applying semi-simultaneous saccharification and fermentation showed the highest conversion rate: 58.9% in 7.0% NaOH pretreated samples. However, after considering the weight loss of bamboo samples during pretreatment, the 1.0% NaOH pretreated sample was indicated as the highest ethanol-producing efficiency with 38.1% conversion rate. These results show that sodium hydroxide is an effective pretreatment in combination with Phlebia sp. MG-60 in bioethanol production from Japanese bamboo, with or without commercial hydrolytic enzymes. Highlights • Sodium hydroxide pretreatment have shown the removal of lignin and xylan. • The saccharification rate of bamboo was increased by the alkaline pretreatment effects. • The first report in consolidated bioprocessing from bamboo was pointed out. • Successful semi-simultaneous saccharification and fermentation using Phlebia sp. MG-60 is introduced. [ABSTRACT FROM AUTHOR]

In the present work, xylan from arecanut husk was extracted using 2 stage alkaline pretreatment process. In first step, biomass was incubated in alkali at different temperatures (25 °C, 50 °C and 65 °C), alkali concentrations (5%, 10%, 15% and 20% w/v), and incubation periods (8 h, 16 h and 24 h) and evaluated for xylan recovery. It was observed that 40–52% of available xylan could be recovered using 10% alkali when incubated for 8–24 h at 65 °C. Subsequently, the alkali pretreatment operating conditions which provided good xylan recovery were processed further using hydrothermal treatment to extract more xylan. For maximum xylan recovery (>90%), best operating conditions were identified when biomass was treated under hydrothermal treatment (1, 1.5 and 2 h) with varying incubation periods (8, 16, 24 h) and alkali concentrations (5%, 10%) using full factorial design. Incubating arecanut husk with 10% w/v NaOH, at 65 °C for a period of 8 h, followed by hydrothermal treatment at 121 °C for 1 h helped recover >94% xylan. In the next step, enzymatic hydrolysis process was optimized to recover maximum XOS (Optimized condition: 50 °C, pH 4 and 10 U enzyme dose). The hydrolysate comprised of xylobiose: 25.0 ± 1.2 g/100 g xylan (∼71% of XOS), xylotriose: 9.2 ± 0.65 g/100 g xylan (26.2% of XOS) and xylotetrose: 0.9 ± 0.04 g/100 g xylan (2% of XOS). The developed process enables to reduce alkali consumption for high recovery of xylan from biomass with relatively higher lignin content for its valorisation into a potential prebiotic oligosaccharide. [ABSTRACT FROM AUTHOR]

Among lignocellulosic residues, peach tree prunings are widely abundant in Italy, due to an extensive production and a high yield of prunings per cultivated hectare; thus, it represents an interesting feedstock for no food derived ethanol. In the whole production process, the pretreatment is the most critical step from technical and economic point of view. In this work peach tree residues were submitted to alkaline pretreatment, in order to maximize the fermentable sugar recovery and thus to maximize the theoretical etOH yield evaluating the best operative conditions in terms of NaOH concentration, temperature, and reaction time. The analysis is carried out by means of Response Surface Methodology approach, in order to optimize the pretreatment step. The optimal predicted conditions to perform the process were NaOH concentration = 0.200 mol dm -3 , temperature = 125 °C and reaction time = 35 min, that allowed to obtain a theoretical ethanol yield of 223 L t -1 of dry peach tree pruning. This theoretical yield can be judged satisfactory in the context of forest and pruning biomass and it could be further increased by a future scale up from laboratory to pilot scale. [ABSTRACT FROM AUTHOR]

Lignocellulosic biomasses such as banana pseudostem are attractive cellulose sources for bioenergy production, and for the use in biorefinery processes. However, pretreatment of lignocellulosic material is required to remove hemicellulose and lignin, while increasing cellulose accessibility to enzymatic hydrolysis (i.e., decreasing biomass recalcitrance). The effect of different concentrations of acid (H 2 SO 4 ), alkaline (NaOH) and peroxide (H 2 O 2 ) pretreatments on the chemical composition, cellulose accessibility, and enzymatic digestibility of banana pseudostem were studied. The water insoluble solids (WIS) recovery was low (∼30%) for the severe pretreatment conditions applied, indicating high material solubilization. Acid pretreatment completely removed the hemicellulose content, whereas alkaline and peroxide pretreatments reduced its amount to 4.38 and 8.68%, respectively. In contrast, the lignin content increased (from 17.26 to 39.99%) after severe acid pretreatment, while alkaline and peroxide pretreatments reduced the lignin content to 7.65% and 7.17%, respectively. In line with hemicellulose and lignin removal, the cellulose content increased from 60.84 to 75.48 and 74.37%, respectively for alkaline and peroxide pretreatments, with no alteration for acid. Dye adsorption assays showed that alkaline and acid pretreatments resulted in high internal and external specific surface areas – indicative of high cellulose accessibility – when compared with peroxide pretreatments. Overall, alkaline and acid pretreatments resulted in the highest glucose yields from enzymatic hydrolysis of banana pseudostem, compared with peroxide pretreatment. In conclusion, concentrations of each pretreatment that led to the highest glucose yields was identified, confirming that the banana pseudostem is a great source of fermentable sugars, with high potential for biofuel production. [ABSTRACT FROM AUTHOR]

Hydrodynamic cavitation (HC) was adopted to assist alkaline-hydrogen peroxide pretreatment of sugarcane bagasse (SCB). In the following condition: 0.29 M of NaOH, 0.78% (v/v) of H 2 O 2 , 9.95 min of process time and 3 bar of inlet pressure, 95.4% of digestibility of cellulosic fraction was achieved. To take the best use of the pretreated biomass, the overall process was intensified by way of employing a packed bed flow-through column reactor and thus enabling to handle a high solid loading of 20%, thereby leading to cellulose and hemicellulose conversions to 74.7% and 75%, respectively. In the fermentation step, a bubble column reactor was introduced to maximize ethanol production from the pretreated SCB by Scheffersomyces stipitis NRRL-Y7124, resulting in 31.50 g/L of ethanol, 0.49 g/g of ethanol yield and 0.68 g/L.h of productivity. All this showed that our HC-assisted NaOH-H 2 O 2 pretreatment strategy along with the process intensification approach might offer an option for SCB-based biorefineries. [ABSTRACT FROM AUTHOR]

Alkaline pretreatment with NaOH was used to improve methane yield from Pennisetum Hybrid . The pretreatments were carried out with different NaOH solutions (2–8% w/w) at three temperatures (35, 55 and 121 °C) for different periods of time (24, 24 and 1 h). All treated and untreated Pennisetum Hybrid were digested under mesophilic conditions (37 °C) to biogas, significant effects of the pretreatments on the yield of methane were observed. Results showed the modified Gompertz equation was reliable (determination coefficients (R 2 ) greater than 0.96) to describe the kinetic behavior of anaerobic digestion of Pennisetum Hybrid . The best result, obtained by the treatment at 35 °C 2% NaOH for 24 h, resulted in the methane yield of 301.7 mL/g VS, corresponding to 21.0% improvement in the methane yield. Compositional, SEM, XRD and FTIR analysis confirmed that lignin removal, structural modification and cellulose crystalline variation were responsible for the improvement. [ABSTRACT FROM AUTHOR]

This work investigated the effect of three different chemical pretreatment methods on the biogas production from the anaerobic digestion of wheat straw. The lignocellulosic material was separately pretreated using i) the organic solvent N-methylmorpholine N-oxide (NMMO) at 120 °C for 3 h, ii) the organosolv method, employing ethanol as the organic solvent at 180 °C for 1 h and iii) using an alkaline pretreatment with NaOH at 30 °C for 24 h. All the pretreatments were effective in increasing the biomethane production yield of wheat straw. In particular, the cumulative biomethane production yield of 274 mL CH 4 /g VS obtained with the untreated feedstock was enhanced by 11% by the NMMO pretreatment and by 15% by both the organosolv and alkaline pretreatment. The three pretreatment methods had a different impact on the chemical composition of the straw. NMMO hardly changed the amount of carbohydrates and lignin present in the original feedstock. Organosolv had a major impact on dissolving the hemicellulose component, whereas the alkaline pretreatment was the most effective in removing the lignin fraction. In addition to the increased biogas yields, the applied pretreatments enhanced the kinetics of biomethane production. [ABSTRACT FROM AUTHOR]

The effect of trace elements (TEs) addition and NaOH pretreatment on the anaerobic digestion of rice straw was investigated in batch tests. Co, Ni and Se were added to the raw rice straw at different dosages. The NaOH pretreatment was applied to the rice straw both alone and in combination with the addition of TEs, in order to evaluate potential synergistic effects of the pretreatment and the TEs supplementation on the biogas production yields. The results obtained showed that the alkaline pretreatment was more effective than the TEs addition in increasing the cumulative biogas production, causing a 21.4% enhancement of the final biomethane yield, whereas the increase due to TEs dosing was not statistically significant. The analysis of volatile fatty acids (VFAs) confirmed that the NaOH pretreatment resulted in a higher production of VFAs, indicating an increased hydrolysis, while TEs addition did not cause significant changes in the VFA concentrations. [ABSTRACT FROM AUTHOR]

A sequential two-stage pretreatment process comprising alkaline pre-extraction and alkaline hydrogen peroxide pretreatment (AHP) was investigated to convert bamboo carbohydrates into bioethanol. The results showed that mild alkaline pre-extraction using 8% (w/w) sodium hydroxide (NaOH) at 100 °C for 180 min followed by AHP pretreatment with 4% (w/w) hydrogen peroxide (H 2 O 2 ) was sufficient to generate a substrate that could be efficiently digested with low enzyme loadings. Moreover, alkali pre-extraction enabled the use of lower H 2 O 2 charges in AHP treatment. Two-stage pretreatment followed by enzymatic hydrolysis with only 9 FPU/g cellulose led to the recovery of 87% of the original sugars in the raw feedstock. The use of the pentose-hexose fermenting Saccharomyces cerevisiae SR8u strain enabled the utilization of 95.7% sugars in the hydrolysate to reach 4.6% w/v ethanol titer. The overall process also enabled the recovery of 62.9% lignin and 93.8% silica at high levels of purity. [ABSTRACT FROM AUTHOR]

The specific characteristics of biomass structure and differences in chemical composition of soybean hull (SBH) and soybean straw (SBS) may result in different behavior of pretreatment and enzymatic hydrolysis. In this work, dilute sulfuric acid (DA) pretreatment and alkaline sodium hydroxide (AL) pretreatment in a range of pretreatment temperatures and durations were investigated to improve the enzymatic digestibility of SBH and SBS. Satisfactory enzymatic digestibility was observed in the hydrolysis of both pretreated soybean fractions, but SBH showed higher digestibility than that of SBS, no matter which pretreatment technology was applied. Furthermore, DA pretreatment was more effective than AL pretreatment in conversion of soybean fractions into fermentable sugars, if both pretreatment and enzymatic hydrolysis stages were considered. The highest total sugar yield of SBH and SBS using DA pretreatment and subsequently hydrolyzed with 30 FPU/g-DM cellulase were 86.9% and 70.3%, respectively. [ABSTRACT FROM AUTHOR]

This study evaluated the synergistic efficiency of crude enzymatic extracts (CEE) produced by fungal strains Aspergillus fumigatus SCBM6 (AFE) and Aspergillus niger SCBM1 (ANE) in the hydrolysis of alkali pretreated sugarcane bagasse (2% NaOH (w v −1 ), ∼100 °C, 4 h and liquid-to-solid ratio of 25 (v w −1 )). CEEs were produced by solid-state fermentation (SSF) and presented high concentration of β-glucosidase (AFE = 78.4 U g −1 and ANE = 43.02 U g −1 ), β-xylosidase (ANE = 78.0 U g −1 ) and xylanase (AFE = 1774.5 U g −1 and ANE = 3289.6 U g −1 ). A 2 4 full design of experiments was used to optimize the hydrolysis of pretreated bagasse as a function of time, temperature, amount of pretreated bagasse and AFE-to-ANE ratio. After hydrolysis optimization, the maximum concentration of total reducing sugars (TRS) was 21.68 g L −1 . It was also noticed a significant production of xylose (135.59 mg) and arabinose (58.10 mg) per gram of hemicelluloses and a slight production of glucose (20.18 mg) per gram of cellulose. As fungi consortium were excellent producers of hemicellulases, it is suggested that they could be used for pentoses saccharification and production of ethanol via C-5 fermentation, xylitol, biopolymers, among other bioproducts. [ABSTRACT FROM AUTHOR]

Complete cycle of ethylene production from oat hulls as widespread agricultural waste was studied on a pilot scale. The cycle involved mechano-chemical, biotechnological and catalytic units. The oat hulls were pretreated with a 2%(w/w) sodium hydroxide solution in a setup consisting of a rotary-pulsating apparatus and a 100-L vessel to produce a pulp containing 90.3% of hydrolyzables. Simultaneous saccharification and fermentation of oat hull pulp with delayed inoculation (dSSF) into ethanol using commercial enzymes CelloLux-A and BrewZyme-BGX and non-GMO yeast Saccharomyces cerevisiae was carried out in 63-L reactor . At a solid loading of 33.3 g/L, the yield of reducing sugars was 97.9% on overall hydrolyzables basis. The ethanol yield during dSSF at a solid loading of 60 g/L was as high as 95 g ethanol/kg oat hulls. The produced raw-ethanol sample contained low impurities of methanol, propanol and alkali metals. The rectified ethanol samples were used for dehydration to ethylene with the overall production index as high as 38–51 g ethylene/kg oats hulls. A negative impact of the propanol and alkali metals impurities in the rectified ethanol on conversion and selectivity to ethylene were observed. Being purified from organic impurities, ethanol was dehydrated with higher conversion and selectivity to ethylene. When the ethanol samples that contain less than 0.02 g/L organic and no sodium impurities were used in ethanol dehydration process, the yield of ethylene was as high as 56 g ethylene/kg oats hulls. In this work, 12 kg of oat hulls was converted to 1.21 kg 94%(w/w) ethanol, which was then converted to 0.62 kg 99.5% ethylene; this is the first experimental study devoted to the production of ethylene from oat hulls on a pilot scale. [ABSTRACT FROM AUTHOR]

Biotechnologically produced itaconic acid is an important building block for the chemical industry and still based on pure carbon sources, detoxified molasses or starch hydrolysates. Changing these first generation feedstocks to alternative renewable resources of a second generation implies new challenges for the cultivation process of the industrial itaconic acid producer Aspergillus terreus , which is known to be very sensitive towards impurities. To select a suitable pretreatment method of a second generation feedstock, the influences of different hydrolysate components, like monosaccharides and sugar degradation products, were tested. Particular the impact of those components on itaconic acid yield, productivity, titer and morphology was investigated in detail. Wheat chaff was used as lignocellulosic biomass, which is an agricultural residue. An alkaline pretreatment method with sodium hydroxide at room temperature and a subsequent enzymatic saccharification at pH 4.8 at 50 °C with 10 FPU/g Biomass Biogazyme 2x proved to be very suitable for a subsequent biotechnological production of itaconic acid. A purification by a cation exchanger of the wheat chaff hydrolysate resulted in a final titer of 27.7 g/L itaconic acid with a yield of 0.41 g/g total sugar . [ABSTRACT FROM AUTHOR]

[Display omitted] • Pretreatment with SL and NaOH increased enzymatic hydrolysis efficiency of WS. • Increment of xylan and lignin removal of WS was 6.5% and 26.8% by SL. • Synergy between SL and NaOH enhanced efficiency of hydrothermal pretreatment. Surfactant-assisted pretreatment has been widely reported to improve the enzymatic hydrolysis of lignocellulose by promoting removal of xylan and lignin. Hence, this work innovatively proposed the use of sodium lignosulfonate (SL) as an additive of alkaline pretreatment (AP), and evaluated its influence on the cellulosic digestibility of wheat straw (WS). The results displayed that the maximum of 72-h cellulosic digestibility could reach 83.5% as 15 g/L SL was introduced to the AP process (SAP), while the cellulosic digestibility of hydrothermal and alkaline pretreated WS was only 63.6% and 70.2%, respectively. These increments were subsequently attributed to the improvement of 6.5% xylan and 26.8% lignin accelerated by SAP, resulting in positive changes in structural characteristics such as accessibility, specific surface area, and cellulosic crystalline structure. The utilization of lignin-based surfactants in pretreatment has realized the economic feasibility of lignocellulosic biorefining and broadened the application prospect of surfactants. [ABSTRACT FROM AUTHOR]

[Display omitted] • Torrefaction with alkali addition for wheat straw pretreatment was investigated. • A 41 % increase in methane yield was obtained at the optimal conditions. • Alkali addition enhanced the humification of the digestates. • Most of the N (84.5 %) and K (93.4 %) were recovered in the digestates. • Solar powered alkali/torrefaction system could further improve economic benefits. Low-temperature torrefaction assisted with solid-state KOH/urea applied onto wheat straw was proposed to break down the lignocellulosic material to enhance biomethane production in anaerobic digestion (AD). The optimization of key parameters applying the Box-Behnken design and response surface methodology showed that an addition of 0.1 g/g straw KOH/urea at 180 °C while torrefying for 30 min was the optimal condition for producing biomethane. Results indicate that co-applying KOH and urea in torrefaction synergistically enhanced the biodegradability of straw by effectively removing lignin and largely retaining cellulose, giving rise to a 41 % increase in the cumulative methane production compared to untreated straw (213 mL/g-volatile solids (VS raw)) from batch AD. Additionally, the nitrogen- and potassium-rich digestates helped to improve soil fertility, thus achieving a zero-waste discharge. This study demonstrated the feasibility of using solid-state KOH/urea assisted low-temperature torrefaction as an effective pretreatment method to promote methane production during AD. [ABSTRACT FROM AUTHOR]

The presence of lignin in lignocellulosic biomass leads to a protective barrier that prevents plant cell destruction by fungi and bacteria for conversion to bio-methane gas. Therefore, the aim of this study was to evaluate the effects of upgraded seawater with NaOH, NaCO 2 and palm kernel ash (PKA) to produce the best alkaline solution in order to convert lignin and increase the fermentable sugars content in oil palm empty fruit bunch (OPEFB). In this study, alkaline pretreatment of EFB is carried out at room temperature using different concentration of alkaline solution which are 5%, 10%, 15% and 20% w/v of chemical (NaOH, Na 2 CO 3 and PKA) and seawater for 48 hours. OPEFB in a size of 0.5 – 1.0 mm was soaked into the NaOH and Na 2 CO 3 solution for 48 hours at room temperature. The surface morphology analysis of lignocellulosic biomass after pre-treatment were done by using scanning electron microscopic (SEM). Analysis of delignification using Kappa Number showed that the highest percentage of delignification were 86.6%, 69.8% and 58.8% by using concentration of 5% NaOH, 15% Na 2 CO 3 and 20% PKSA, respectively. Morphological change on OPEFB was found when silica was cracks and creating a pore during pre-treatment. This significant increase in reducing sugar yields due to removal of silica and lignin. The results of FTIR showed lignocellulose were removed effectively from EFB fiber. This observation also supported FTIR and SEM analysis that showed significant changes in lignin structure throughout the pre-treatment process. Interestingly, with respect to all factors, upgraded seawater with NaOH demonstrated the highest delignification and fermentable sugar production. [ABSTRACT FROM AUTHOR]

Alkaline pretreatment for lignocellulosic biomass is beneficial for enhancing the anaerobic digestibility, but the rise of pretreatment cost and the dilution of substrate by the addition of a neutralizing agent and an alkaline solution are significant drawbacks. To solve these problems, utilization of acidified food waste as a co-substrate during anaerobic digestion of alkali-pretreated submerged macrophytes was attempted under various macrophyte to food waste (MF) ratio, and the biochemical interactions between the co-substrates were investigated. The addition of acidified food waste dropped the pH of alkali-pretreated Potamogeton maackianus , which reduced the dosage of neutralizing agent by 50% at MF 1:1. In co-digestion experiment, more CH 4 was produced as the dosage of food waste increased. Volatile-solid-based and wet-weight-based CH 4 yields for MF 1:1 were 37% and 118% higher than those for the alkali-pretreated macrophyte, respectively, because of the high degradability and organic matter content of the food waste. Comparison between the measured and theoretical COD balance of the co-digestion revealed that there is no positive synergistic effect in the CH 4 recovery. Instead, the hydrolysis of the co-substrates is inhibited possibly due to the existence of dissolved lignin. Overall, the study demonstrates that anaerobic co-digestion of alkali-pretreated macrophytes and acidified food waste could be a feasible option for reducing the neutralizing agent cost and enhancing the volumetric CH 4 yield. [ABSTRACT FROM AUTHOR]