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The present study evaluates the potential of green coconut fiber in the production of cellulosic butanol by ABE (acetone-butanol-ethanol) fermentation, using Clostridium beijerinckii ATCC 10132. Batch fermentation tests were carried out to investigate the influence of some nutrients (sources of nitrogen and mineral medium) in the supplementation of the enzymatic hydrolyzate of pretreated green coconut husks, as well as the effects of the initial concentration of sugars and the initial concentration of inoculum on the production of butanol among other fermentation products. The mode of conducting the process in a fed-batch was carried out to improve the yield and productivity of butanol. Using the enzymatic hydrolyzate obtained with 9 g/L of sugars (glucose + xylose), the ABE fermentation reached a yield of 0.53 g/g after 96 h, in which 3.4 g/L of butanol was obtained. The absence or insufficiency of some nutrients (minerals and phosphate buffer) resulted in low yields of ABE products, indicating the importance of adapting supplements to the chosen fermentation medium and the type of microorganism used. Fed-batch increased productivity in ABE fermentation (0.08 g/L.h for butanol). The results indicate that green coconut residues have energy potential and are low-cost raw materials for the biotechnological production of butanol, as an alternative and renewable product. [ABSTRACT FROM AUTHOR]

The unwashed alkali-treated lignocellulose can be directly enzymatically hydrolyzed and fermented via pH adjustment with acids. The use of acids would give a burden on production cost. Furfural residue (FR) which is the acidic solid waste from lignocellulose-derived furfural production process was employed in this study as a pH regulator. The corn cob-derived FR was used to adjust the pH value of alkali-treated corn stover (PCS) to 4.8 for enzymatic hydrolysis and ethanol fermentation. The unwashed PCS adjusted by FR got higher enzymatic hydrolysis efficiency (EHE) than the washed PCS samples. Meanwhile, the mixing of PCS and FR had a synergistic effect on the EHE of PCS. The fermentation of enzymatic hydrolysate from unwashed PCS-FR mixture at 20% solid concentration could attain ethanol production of 26.54 ± 0.02 mg/mL with a yield of 89.53 ± 0.08%. This work created a novel recycling way of FR as a pH regulator for improving the bioconversion of alkali-treated lignocellulose. It also provided a novel clue for the valuable valorization of wastes from corn production. [ABSTRACT FROM AUTHOR]

Xylooligosaccharides (XOS) are potential prebiotic ingredients for food industries, mainly obtained after xylan hydrolysis by endoxylanases. Enzyme immobilization offers opportunities for recovery and reuse, while also enhancing its physical and chemical characteristics, such as stability and catalytic efficiency. This work aimed to immobilize the SM2 xylanase derived from the xynA gene from Orpinomyces sp. PC-2 and to evaluate its potential for XOS production. For this, SM2 xylanase was immobilized using the cross-linking methodology. The free and immobilized enzymes were characterized regarding the effect of pH, temperature, and thermostability. The cross-linked enzyme aggregate was evaluated for reuse and storage conditions and used for xylooligosaccharide production. Both free and immobilized SM2 xylanase showed maximal activity at 60 °C. The immobilized enzyme was more active at acidic and neutral conditions, and the free enzyme showed greater activity at basic conditions. The half-life of the free and immobilized xylanase was 30 and 216 h, respectively. In reuse tests, enzymatic activity increased with each cycle, and there was no statistical difference in the activity of SM2 xylanase aggregate stored at 4 and 25 °C. After saccharification, xylobiose (0.895 g/L), xylotriose (0.489 g/L), and xylohexose (0.809 g/L) were detected. As a result, immobilization enhanced thermostability, shifted the pH of maximum activity to 5, facilitated reuse, and eliminated the need for refrigerated packaging. Finally, the xylooligosaccharides produced by the SM2 xylanase are known for their prebiotic role, providing potential application of the immobilized enzyme in the food industry. [ABSTRACT FROM AUTHOR]

Biomass pretreatment for the production of second-generation (2G) ethanol and biochemical products is a challenging process. The present study investigated the synergistic efficiency of purified carboxymethyl cellulase (CMCase), β-glucosidase, and xylanase from Aspergillus fumigatus JCM 10253 in the hydrolysis of alkaline-pretreated sugarcane bagasse (SCB). The saccharification of pretreated SCB was optimised using a combination of CMCase and β-glucosidase (C + β; 1:1) and addition of xylanase (C + β + xyl; 1:1:1). Independent and dependent variables influencing enzymatic hydrolysis were investigated using response surface methodology (RSM). Hydrolysis using purified CMCase and β-glucosidase achieved yields of 18.72 mg/mL glucose and 6.98 mg/mL xylose. Incorporation of xylanase in saccharification increased the titres of glucose (22.83 mg/mL) and xylose (9.54 mg/mL). Furthermore, characterisation of SCB biomass by scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy respectively confirmed efficient structural disintegration and revealed the degree of crystallinity and spectral characteristics. Therefore, depolymerisation of lignin to produce high-value chemicals is essential for sustainable and competitive biorefinery development. [ABSTRACT FROM AUTHOR]

AbstractThe aim of this work is to investigate the influence of an alkaline pretreatment of the Mediterranean plant Carpobrotus edulis on the adsorption capacity toward the dye methylene blue and to estimate the content of soluble organic matter that can be released into the aqueous solution by this biomaterial. The biomaterial used was characterized by SEM-EDX, SS, FT-IR, pHZ, COD and BOD5. Removal of methylene blue (MB) dye by this biomaterial was carried out and the effects of physicochemical factors such as initial pollutant concentration, adsorbent dose, contact time, pH and temperature were investigated. After adsorbent treatment, the soluble organic matter was reduced by 97%, 96%, and 96% for biological oxygen demand, chemical oxygen demand, and organic matter, respectively. Kinetics and equilibrium studies of MB adsorption on the bioadsorbents were fitted with a pseudo-second order kinetic model and a Langmuir model, respectively. The maximum adsorption amount of the modified C. edulis plant was 153.9 mg/g at 298°K. The thermodynamic parameters show that the adsorption process was possible and spontaneous in nature. The adsorption mechanism of MB on the surface of biomaterials was attributed to the electrostatic interaction and H-bonding. The prepared biomaterial (0.016 U$ per gram) was easily regenerated with aqueous HNO3 solution, with a slight decrease in adsorption capacity up to five cycles. The results of Taguchi experimental design and analysis of variance showed that contact time, adsorbent mass and initial concentration are the most important factors affecting the removal efficiency with a contribution of 43.91%, 32.68%, and 22.95%, respectively. The maximum removal capacity of MB dye in optimal operating conditions was 99.39%, which was obtained at the optimum conditions of m = 1 g, pH 4, T = 35 °C, Ci = 1000 mg/L, tc = 5 min. These results confirm previous results obtained with the batch system and show that this absorbent is also promising for the removal of cationic dyes from wastewater. [ABSTRACT FROM AUTHOR]

In this paper, the effects of an ultrasonic power and the intensity of mechanical agitation for pulp on alkaline pretreatment of gold-bearing arsenopyrite were investigated. The effect of pulp temperature on leaching efficiency in alkaline pretreatment of arsenopyrite was investigated under ultrasound and non-ultrasound conditions. Pre-treatment was followed by gold leaching tests with a cyanide solution. Compared with the nonultrasound condition at the temperature of 60 ○C, arsenic extraction and gold extraction was increased 20 %, 14.4 %, respectively, in the presence of ultrasound at ambient temperature. The characteristics of the ultrasonic power level as a function of the intensity of mechanical agitation were evaluated by a numerical simulation with CFD software – Ansys Fluent. The simulation results demonstrated that the stronger intensity of mechanical agitation, the lower ultrasonic power level. These results were proved through leaching experiments at different rotation speeds of impeller and ultrasonic powers. The study results demonstrate that the ultrasound is an effective factor for pretreatment of gold bearing arsenopyrite and gold extraction is related to an ultrasonic power and the intensity of mechanical agitation. [ABSTRACT FROM AUTHOR]

The present work studied the effects of alkali pretreatment on the cellulosic biomass of rice straw. The improvement in the cellulose content and reduction in the lignin and hemicellulose percentage was observed with alkali pretreatment. Fourier transformation infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM) analysis confirm the modification in the surface structure of alkali rice straw. Further, the study investigated the potential of different types of seed sludge as inoculum sources for dark fermentative biohydrogen production. In comparison to other sludge samples (beverage industry, food industry, and sewage treatment plant sludge), the mixed culture of sewage treatment plant sludge had the highest cumulative volume of biohydrogen (90.52 mL), as well as the highest hydrogen production yield (0.75 moleH2/mole) with the substrate utilization of 86.72%. The results provide information on the best sludge source for enhancing biohydrogen production in the dark fermentation method. [ABSTRACT FROM AUTHOR]

Banana (Musa acuminata) cultivation and trade are widespread across various regions and countries globally. Nonetheless, substantial quantities of waste, primarily comprising leaves and stems of the banana plant, are annually disposed of into the environment post-harvest. This study aims to highlight this issue and propose an alternative solution in response to the escalating demand for raw materials. To this end, alkaline pretreatment was administered to particles derived from banana waste leaves and stems using NaOH solutions at concentrations of 1%, 3%, and 5%, followed by board production. Results indicate that water absorption (WA) and thickness swelling (TS) values of the produced boards increased with alkaline treatment. However, the mechanical properties stipulated in the TS-EN 312 (2012) standard were satisfactorily achieved with 1% NaOH treatment, while higher concentrations adversely affected internal bond strength (IB), modulus of elasticity (MOE), and modulus of rupture (MOR). In the surface properties tests of the boards, increasing the alkali concentration decreased values of the surface roughness and the contact angle. Overall, the findings suggest the viability of utilizing banana waste as an alternative resource.

Spent mushroom compost is one of the main potentials for biogas production. In recent years, several studies employed adding nanoparticles and alkaline pretreatment for improving biogas production. The present study is one of the pioneer studies that employ hybrid alkaline pretreatment (0, 5, and 15 mg of NaOH) and zero-valent iron nanoparticles (0, 10, 20, 30, and 40 mg) for improving the co-digestion of spent mushroom compost and rice straw. According to the results, retention time (RT) and nanoparticle (NP) concentrations have the most significant impact on biomethane production (significant at 1% probability level), while the NaOH concentration has the lowest impact on biomethane production (significant at 5% probability level) in comparison with RT and NP concentration. Also, the maximum biomethane production is related to NP40Na15 (about 200% higher than the control). The minimum cumulative biomethane production is related to NP0Na15 (about 30% lower than the control). The lowest relative environmental midpoint impact is related to NP40Na15, which was on average about 60% lower than the control. Adding NPs at high concentrations of NaOH reduces the midpoint impacts. The results of the study could lead to new, ecologically friendly biomethane production methods that make better use of agricultural and organic wastes.

Alkaline pretreatment stands out as a valuable strategy in biomass conversion to overcome the recalcitrance of biomass by removing lignin and a part of hemicellulose. This enhances enzyme accessibility and promotes saccharification. However, increasing the alkaline concentration to enhance the delignification and improve glucose yield together presents inherent limitations. In this experiment the amount of delignification and glucose yield resulting from surfactant associated with sonication during mild alkaline pretreatment of Eucalyptus pellita was investigated. Also, the effect of various factors (sonication temperature and surfactant immersion time) on delignification and glucose yield were examined. The results demonstrated that surfactant associated with sonication pretreatment could overcome the limitation of alkaline pretreatment and could increase the amount of delignification alongside enzymatic hydrolysis glucose yield of Eucalyptus pellita wood by around 90%. The findings indicated that surfactant-assisted with sonication during mild alkaline pretreatment of Eucalyptus pellita (i.e., hardwood) could be recommended as a supporting pretreatment method for the production of monomeric sugars. [ABSTRACT FROM AUTHOR]

This review paper examines acid and alkaline pretreatments on perennial grasses for second-generation (2G) bioethanol production, a relatively unexplored area in this field. It compares the efficiency of these pretreatments in producing fermentable sugar and bioethanol yield. This study finds that alkaline pretreatment is more effective than acidic pretreatment in removing lignin and increasing sugar yield, leading to higher ethanol yields. However, it is costlier and requires longer reaction times than acidic pretreatment, while acidic pretreatment often leads to the formation of inhibitory compounds at higher temperatures, which is undesirable. The economic and environmental impacts of lignocellulosic biomass (LCB) are also assessed. It is revealed that LCB has a lower carbon but higher water footprint and significant costs due to pretreatment compared to first-generation biofuels. This review further explores artificial intelligence (AI) and advanced technologies in optimizing bioethanol production and identified the gap in literature regarding their application to pretreatment of perennial grasses. This review concludes that although perennial grasses hold promise for 2G bioethanol, the high costs and environmental challenges associated with LCB necessitate further research. This research should focus on integrating AI to optimize the pretreatment of LCB, thereby improving efficiency and sustainability in 2G biofuel production. [ABSTRACT FROM AUTHOR]

In order to improve the biogas production from sweet sorghum bagasse (SSB) pretreated with alkaline hydrogen peroxide and reveal the influence of zeolite dosage and TE on the anaerobic digestion performance, as well as the synergistic effect of zeolite dosage and TE, three dosages of zeolite and trace elements (TE) were used as additives for batched biogas production from pretreated sweet sorghum bagasse slurry (PSSBS). The results showed that the maximum methane production of 274.5 mL/g volatile solid (VS) from the group of PSSBS + 5 g/L zeolite + 1 mL TE could be obtained and 58.4% higher than that of untreated sweet sorghum bagasse. Modified Gompertz model estimation demonstrated that the PSSBS + 5 g/L zeolite + 1 mL TE group caused the highest methane production rate to improve by up to 41.6% from SSB and by at least 39.9% from PSSBS. Moreover, with the zeolite and TE addition, activities of cellulase and dehydrogenase of the digestate analysis indicated a positive influence on biogas production and the high alkalinity maintained the stability of the system. This work will provide experimental reference for biogas production from sweet sorghum bagasse. [ABSTRACT FROM AUTHOR]

Alkaline pretreatment stands out as a valuable strategy in biomass conversion to overcome the recalcitrance of biomass by removing lignin and a part of hemicellulose. This enhances enzyme accessibility and promotes saccharification. However, increasing the alkaline concentration to enhance the delignification and improve glucose yield together presents inherent limitations. In this experiment the amount of delignification and glucose yield resulting from surfactant associated with sonication during mild alkaline pretreatment of Eucalyptus pellita was investigated. Also, the effect of various factors (sonication temperature and surfactant immersion time) on delignification and glucose yield were examined. The results demonstrated that surfactant associated with sonication pretreatment could overcome the limitation of alkaline pretreatment and could increase the amount of delignification alongside enzymatic hydrolysis glucose yield of Eucalyptus pellita wood by around 90%. The findings indicated that surfactant-assisted with sonication during mild alkaline pretreatment of Eucalyptus pellita (i.e., hardwood) could be recommended as a supporting pretreatment method for the production of monomeric sugars.

The Vietnamese food industry produces a lot of coffee pulp, which is a valuable and abundant source of agricultural by-products. It contains a lot of cellulose, which can be converted into bioethanol. However, coffee pulp needs an extensive pretreatment to reduce the amount of lignin and hemicellulose while retaining the initial cellulose composition. This study compared several pre-hydrolysis and pre-fermentation pretreatment methods which involved H2 SO4 , NaOH, microwaves, and white rot fungus Phanerochaete chrysosporium. The hemicellulose dropped by 43.8% after the acidic pretreatment, by 47.1% after the alkaline pretreatment, and by 12.8% after the microbial pretreatment. The lignin contents dropped by 4.2, 76.6, and 50.2% after acidic, alkaline, and microbial pretreatment, respectively. The removal of hemicellulose and lignin in the coffee pulp was much more efficient when two or three of the pretreatment methods were combined. The microwave-assisted acid and alkaline pretreatment was the most efficient method: it removed 71.3% of hemicellulose and 79.2% of lignin. The combined method also had the highest amount of reducing sugars and glucose in hydrolysate. Additionally, concentrations of such yeast inhibitors as 5-hydroxymethyl-2-furaldehyde (HMF) and furfural were 2.11 and 3.37 g/L, respectively. The acid pretreatment was effective only in removing hemicellulose while the alkaline pretreatment was effective in lignin removal; the fungal pretreatment had low results for both hemicellulose and lignin removals. Therefore, the combined pretreatment method was found optimal for coffee pulp.

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A facile and highly efficient method was proposed for the separation and regeneration of LiFePO4 (LFP) cathode materials from spent lithium‐ion batteries (LIBs). The optimal separation conditions involved immersing the spent LFP materials in NaOH (0.5 mol/L) solutions at a temperature of 90 °C, with a solid‐liquid ratio of 30 g/L under stirring of 500 rpm. The high separation effect can be attributed to the synergistic action of several factors at the interface. Furthermore, the structure, composition, morphology, and electrochemical performance of the regenerated LFP (D‐LFP) materials at different temperatures were systematically investigated. Notably, the D‐LFP material generated through calcination at 650 °C for 10 h exhibited a initial discharge capacity of 154.4 mAh g−1 at 0.5 C and the capacity retention rate of 97.3 % after 100 cycles. Moreover, a detailed investigation of the kinetics of the separation and regeneration processes was carried out, along with an exploration of the underlying electrochemical mechanism. This idea not only mitigates the harmful impact of waste on both human health and the environment but also realizes the transformation of waste into valuable resource treasure, promoting a greener and more sustainable development of society. [ABSTRACT FROM AUTHOR]

Second-generation (2G) ethanol is obtained from the processing of lignocellulosic biomasses, such as sugarcane bagasse. However, several obstacles need to be overcome to make the industrial fermentation of the sugarcane bagasse hydrolysates viable, such as the time and capital expense of the process when compared with first-generation (1G) ethanol (produced by sugary and starchy raw materials), the inhibitors generated, and the process scaling-up. The intrinsic release of inhibitor compounds during the deconstruction of lignocellulosic material into sugars is one of the biggest challenges in the fermentation step. Cell immobilization can be used as a strategy to protect microorganisms from these inhibitory compounds. Immobilization can add costs to the process; therefore, the use of materials already available in the ethanol production is interesting from an economic point of view. In this sense, the objective of this study was to evaluate the immobilization of Spathaspora passalidarum in raw, alkaline, and acid-pretreated sugarcane bagasse. In addition, the fermentation of hemicellulosic hydrolysate (HH) from acid pretreatment of sugarcane bagasse was evaluated by immobilized and the free cells. Fermentation by S. passalidarum immobilized on sugarcane bagasse obtained growth and product yield factor of YP/S (0.35 g/g) and YX/S (0.43 g/g), respectively, against YP/S (0.27 g/g) and YX/S (0.086 g/g) for the cell-free assay. After 24 h of fermentation, it was possible to reach a productivity of 0.153 g/(L·h) and a yield of 68.37% with immobilized cells, which were also superior to the fermentation with free cells (0.148 g/(L·h) and 54%). Based on the results, it was possible to verify that sugarcane bagasse can be used not only as an effective source of carbon for the production of 2G ethanol, but also as a support for cell immobilization, increasing the productivity of the process. [ABSTRACT FROM AUTHOR]

The main goal of this work was to study alkaline pretreatment of hazelnut shells (HSs) by utilization of NaOH and Ca(OH)2 with or without glycerol. The highest lignin recovery was obtained for NaOH-glycerol-pretreated HSs. This research also determined the efficiency of enzymatic hydrolysis where xylanase and cellulase were added to the pretreated residue. The highest amount of lignin of 63.2% was achieved when NaOH was used with glycerol in the pretreatment process. These findings revealed that the NaOH-catalyzed glycerol pretreatment applied in this study has great capability to be used in industrial applications. [ABSTRACT FROM AUTHOR]

Bioethanol is obtained by hydrolysis of sugarcane bagasse by cellulases. Commercial cellulases are expensive and have a low concentration of β-glucosidase (EC 3.2.1.21), which decrease hydrolysis efficiency. The present work aims to produce supernatant rich in β-glucosidase (BGL) using the yeast Rhodotorula oryzicola and apply it in the hydrolysis of delignified sugarcane bagasse. Yeast fermented in a modified YPD (Yeast Peptone Dextrose) medium with 0.5% (w/v) cellobiose and 1.0% (w/v) glucose produced BGL with a specific activity of 1.44 ± 0.013 U/mg. Partial purification of BGL by acetone showed a specific activity of 3.48 U/mg. The optimum pH and temperature were 6.02 and 65 °C, respectively. BGL partially purified (BGLppR.oryzicola) by acetone showed tolerance to glucose, with a relative activity of 82.89 ± 0.11%. The activity increased with the addition of iron sulfate and zinc sulfate and decreased with manganese sulfate. BGL partially purified was thermal stable, with a relative activity of 85.59% after 60 min at 90 °C. BGL partially purified applied in the hydrolysis of sugarcane bagasse delignified with 3% (w/w) NaOH + 6% (w/w) Na2SO3 showed a conversion rate of 72.46 ± 1.60%. The results showed that BGL partially purified is a glucose tolerant cellulase of low-cost, promising the application of bioethanol production. [ABSTRACT FROM AUTHOR]

The effects of alkaline pretreatment of walnut shells (WS) utilizing NaOH, Ca(OH)2, or KOH were studied. The highest lignin recovery was obtained from WS pretreated with NaOH‐glycerol. The optimum lignin recovery after pretreatment could be achieved when the NaOH/solid value was 20:1 (mL g−1). CaCl2 loading could enhance lignin flocculation, which improved the lignin recovery. Also, the efficiency of enzymatic hydrolysis was determined when xylanase and cellulase were added to the pretreated residue. WS pretreated in NaOH‐water and NaOH‐glycerol solutions were found to result in the highest xylose and glucose concentrations. This study indicates the broad application prospects of alkaline pretreatment of lignocellulosic biomass in agriculture and industry. [ABSTRACT FROM AUTHOR]

Papyrus (Cyperus papyrus L.) is a lignocellulosic plant suitable for many applications when properly pretreated. This study explores the potential of a two-stage pretreatment (combining hydrothermal and chemical methods) on the characteristics of cellulose fibers derived from papyrus. One-stage and two-stage pretreatments were compared, utilizing sodium hydroxide (NaOH) and ferric chloride (FeCl3) chemical solutions at a 3% (w/v) concentration. Chemical pretreatment was employed for one-stage processing, while hydrothermal pretreatment was introduced prior to chemical pretreatment. As the liquid hot-water process intensified, significant changes in chemical composition and morphology occurred. Hydrothermal pretreatment partially eliminates hemicelluloses and lignin, while increasing the cellulose content and enhancing fiber crystallinity. Following the pulping and bleaching stages, it was determined that the FeCl3-based two-stage pretreatment exhibited the greatest potential for cellulose recovery and hemicelluloses and lignin removal, yielding the highest crystallinity index. [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. [ABSTRACT FROM AUTHOR]

When forests are extensively cleared for infrastructure and agricultural purposes, over half of the wood generated is regarded as waste. To minimize the negative consequences and successfully use renewable energy sources, further applications must be investigated. Biomass has the potential to be converted into biofuels using a process known as hydrothermal liquefaction (HTL). The conversion of wood residue under continuous flow, subcritical HTL, under both untreated and alkaline pretreated conditions was examined in this study. According to the results, pretreatment with 4% NaOH sped up recovery times compared to using raw wood and increased glucose production by 1.8 times (equivalent to 90 g/L) in comparison to using raw wood. Additionally, the fluid's pH was raised from 6.1 to 3.5 due to the alkaline pretreatment, which also switched the hydrolysis of arabinose and cellobiose to rhamnose at 0.2 MPa. The average Net Energy Ratio (NER) for glucose during liquefaction reached values as high as 63%, while the energy output from glucose during the pretreatment reached 246 kJ. The move to green energy transition toward net zero will be aided by these findings, which will usher in new waste conversion techniques to produce sustainable biofuels using continuous flow HTL. [ABSTRACT FROM AUTHOR]

The objective of this study is to synthesize and extensively characterize carboxymethylcellulose from sugarcane bagasse cellulose (CMC-SC) to evaluate its potential use in blend films. A single step of alkaline hydrogen peroxide pretreatment at a low temperature was used to extract cellulose from sugarcane bagasse. The CMC-SC was extensively characterized with respect to its structure, crystallinity, degree of substitution (DS), average molecular weight (Mw), degree of polymerization (DP), viscosity, thermal property, antioxidant property and morphological structure as compared to a commercial CMC (CMC-COM). CMC-SC displays a DS, average Mw and DP of 0.7, 2×106 and 9,204, respectively. The Rapid Visco Analyzer method revealed a relatively low viscosity (65.7 cP) for 4% (w/v) CMCSC solution at 45 °C. A melting temperature (Tm) close to 250 °C was measured, as was a glass transition temperature (Tg ) of 102.4 °C. The DPPH assay indicated that CMC-SC exhibited higher antioxidation activity than CMC-COM. The characterization of the blend films between CMC-SC and polyvinyl alcohol (CMC-SC/PVA) with varying glycerol concentrations showed they had better properties with greater elongation at break than CMC-COM films with or without copolymer blending. [ABSTRACT FROM AUTHOR]

The present research focuses on the experimental study of the effect of alkaline pretreatment with NaOH on biogas production. Different concentrations of NaOH, i.e. 1, 2.5 and 5% (w/w), were tested on the lagoon station's sludge (dry basis) at room temperature for 24 h. The results obtained after 60 days of digestion, through the cumulative volume of biogas recorded, clearly indicate a positive effect of the chemical alkaline pretreatment on the anaerobic digestion since the amount of biogas produced increased by 42.6% when the NaOH concentration was close to 2.5%. This concentration is considered optimal under the chosen conditions. Indeed, inhibition of the methanogenic activity and a blockage of the digestion process are observed beyond this concentration. These results suggest that the alkaline pretreatment can improve the energy efficiency of the obtained biogas (CH4 content) and reduce the residence time. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Torrefaction is known to reduce the logistical costs of biomass. Torrefied biomass’ prospects as feedstock for fermentation to liquid biofuel are largely unknown. This study investigated the interactions of torrefaction and alkaline pretreatment of wheat straw on glucose yields from enzymatic hydrolysis, including treatment order and the potential for pH to play a role in the process. Across a range of torrefaction severities with temperatures of 200 °C, 220 °C, and 240 °C and durations of 20, 40, and 60 min, torrefaction had a negative impact on glucose yield of wheat straw with or without alkaline pretreatment and regardless of the order of alkaline pretreatment. Alkaline pretreatment after torrefaction results in higher glucose yield than alkaline pretreatment before torrefaction, or by torrefaction alone. Hence, there is the prospect for adding logistical benefits of torrefaction to the bioethanol system if alkaline pretreatment is coupled with torrefaction. Decreasing trend in pH with increase in torrefaction severities was observed for trials without buffer, indicating chemical changes causing the decrease in pH might be associated with the reduction in yield.

Studies were carried out on anaerobic digestion of tannery wastewater obtained from leather processing. Degassed activated sludge biomass collected from a wastewater treatment plant was used as source of microorganisms. The study was carried out to examine the impact of alkaline pretreatment on a real tannery wastewater prior anaerobic digestion process. Bio-methane potential tests were conducted at 35±2°C on tannery wastewater pretreated by adding different volumes of 2N NaOH solution up to set pH values at 9, 10, 11, and 12, respectively. NaOH solution addition resulted in a partial removal of total Cr showing efficiency from 16.84 to 95.72% as well as in an increase of the soluble chemical oxygen demand concentration from 8.53 to 29.02%. The effects of this pretreatment affected significantly the results obtained with bio-methane potential tests that showed methane production from all the pretreated tannery wastewater samples much higher than from that unpretreated. Finally, the lag phase duration and the maximum specific methane production rate of the anaerobic digestion process were evaluated by fitting the experimental results from bio-methane potential tests with the following three models: (i) the modified Gompertz model, (ii) the Logistic function, and (iii) the Richards model. All the previous models showed a high level of accordance with the experimental data, even though Richards model resulted in being the most accurate. [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. [ABSTRACT FROM AUTHOR]

Lignocellulosic crop residues have a high energy potential through anaerobic co-digestion (AcoD), due to their carbon content. The lignin content makes them recalcitrant to digestion thus pretreatment is essential. Biological pretreatment (application of enzymes) is of growing interest due to its environmental friendly process. A few studies have been conducted on the direct addition of enzymes. Hence, this study has evaluated the impacts of addition of laccase and lipase- followed by alkaline pretreatment- in the AcoD of highly lignocellulosic substrate- sugarcane bagasse (SB) and readily degradable co-substrate- fruit vegetable waste (FVW). Batch digesters were set-up for digestion at same initial conditions and mesophilic temperature range for both enzymes. Till the end of 81-days long process, lipase produced 1093.6 ml/g-VS cumulative biogas and 80.8% VS reduction. In comparison, laccase produced 988.6 ml/g-VS cumulative biogas (11% less than lipase) and 72.6% VS reduction. The application of lipase enzyme was, therefore, more effective for the stated substrate, as compared to laccase enzyme. Lipase remained more effective, because the concentration of VFA produced in laccase digester was higher, causing lower pH, and hence, process inhabitation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This review paper examines acid and alkaline pretreatments on perennial grasses for second-generation (2G) bioethanol production, a relatively unexplored area in this field. It compares the efficiency of these pretreatments in producing fermentable sugar and bioethanol yield. This study finds that alkaline pretreatment is more effective than acidic pretreatment in removing lignin and increasing sugar yield, leading to higher ethanol yields. However, it is costlier and requires longer reaction times than acidic pretreatment, while acidic pretreatment often leads to the formation of inhibitory compounds at higher temperatures, which is undesirable. The economic and environmental impacts of lignocellulosic biomass (LCB) are also assessed. It is revealed that LCB has a lower carbon but higher water footprint and significant costs due to pretreatment compared to first-generation biofuels. This review further explores artificial intelligence (AI) and advanced technologies in optimizing bioethanol production and identified the gap in literature regarding their application to pretreatment of perennial grasses. This review concludes that although perennial grasses hold promise for 2G bioethanol, the high costs and environmental challenges associated with LCB necessitate further research. This research should focus on integrating AI to optimize the pretreatment of LCB, thereby improving efficiency and sustainability in 2G biofuel production.

Ferulic acid (FA) and p-coumaric acid (pCA) in bagasse, wheat straw, corn straw, and corncob were extracted by alkaline hydrolysis and characterized by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). It was found that the FA and most of the pCA in gramineous biomass could be dissociated and released after being treated with 1 M NaOH at 100°C for 4 h. The yields of pCA/FA in bagasse, wheat straw, corn straw, and corncob determined by GC-FID are 39.8/11.5, 13.7/11.0, 28.0/11.0, and 35.1/14.5 mg/g, respectively. The raw materials and the treated solid residues were characterized by gel-state 2D Heteronuclear Single Quantum Coherence Nuclear Magnetic Resonance (2D HSQC NMR). It was found that only a small amount of lignin was detected in the residue after alkali treatment, indicating that the alkali treatment conditions can effectively cleave the FA and pCA. Additionally, the lignin in the alkali solution was recovered and characterized by 2D HSQC NMR. The FA was not able to be detected by NMR, whereas a small amount of pCA remained in the alkali lignin. This study reveals the structural change of residual lignins during the quantitative isolation of FA and pCA, which is essential for the selective isolation of pCA/FA and valorization of residual alkali lignin. [ABSTRACT FROM AUTHOR]

The pretreatment of lignocellulosic material performed to improve substrate's susceptibility to enzymatic hydrolysis is usually accompanied by reactions leading to the synthesis of compounds that inhibit the metabolic activity of microorganisms. Their toxicity is the main obstacle to the successful bioconversion of lignocellulosic hydrolysates. The identification of these inhibitors and the choice of the optimal detoxication method are crucial for the improving the efficiency of fermentation processes. Material rinsing with water after processing is a common detoxication practice. However, it generates material losses, thus affecting contents of saccharides in the fermentation medium, which may in turn trigger higher costs of lignocellulose conversion to ethanol and other products with a higher added value. A study was undertaken to determine the effect of selected methods for the detoxication of an enzymatic hydrolysate from Miscanthus giganteus on the fermentation efficiency of saccharide derivatives. The experiment conducted with Mucor rouxii DSM 1191 demonstrated the usability of the detoxication method based on the activated carbon. After 96-h fermentation of Miscanthus hydrolysates, the alcohol content in the post-reaction medium was higher by 14% than in the control experiment wherein the material was rinsed with water after pretreatment. The experiment carried out with Saccharomyces cerevisiae 7, NRRL 978 showed no positive impact of the alternative detoxication methods replacing material rinsing on the efficiency of ethanol synthesis. The highest concentration of this metabolite (2.04% (v/v)) was obtained in the experimental variant in which the mentioned operation was coupled with detoxication of hydrolysates using calcium hydroxide. [ABSTRACT FROM AUTHOR]

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]

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. [ABSTRACT FROM AUTHOR]

Torrefaction is known to reduce the logistical costs of biomass. Torrefied biomass' prospects as feedstock for fermentation to liquid biofuel are largely unknown. This study investigated the interactions of torrefaction and alkaline pretreatment of wheat straw on glucose yields from enzymatic hydrolysis, including treatment order and the potential for pH to play a role in the process. Across a range of torrefaction severities with temperatures of 200 °C, 220 °C, and 240 °C and durations of 20, 40, and 60 min, torrefaction had a negative impact on glucose yield of wheat straw with or without alkaline pretreatment and regardless of the order of alkaline pretreatment. Alkaline pretreatment after torrefaction results in higher glucose yield than alkaline pretreatment before torrefaction, or by torrefaction alone. Hence, there is the prospect for adding logistical benefits of torrefaction to the bioethanol system if alkaline pretreatment is coupled with torrefaction. Decreasing trend in pH with increase in torrefaction severities was observed for trials without buffer, indicating chemical changes causing the decrease in pH might be associated with the reduction in yield. [ABSTRACT FROM AUTHOR]

The arousal of environmental concerns due to spike in environmental degradation has necessitated proper waste management and disposal. Arsenic, a potentially toxic element in cassava wastewater, requires treatment prior to the wastewater disposal to minimize environmental pollution and associated health implications. The present study thus addressed the treatment of As5+ heavy metal in cassava wastewater using an efficient biosorbent from chemically pretreated unshelled Moringa oleifera seeds. The effect of various factors influencing the biosorption process for arsenate removal was studied including pH, contact time, biosorbent dosage, and biosorbent pretreatment concentration. The results of Fourier transform infrared spectroscopy clearly suggested that additional functional groups attributed to esters were formed in the pretreated biosorbent, which is responsible for improvement in biosorption. It was found that contact time, biosorbent dosage, and biosorbent pretreatment concentration had statistically significant effect (p values < 0.05) on arsenate removal. A maximum percentage removal of 99.9% was achieved in the synthetic solution at pH 4.0, contact time of 30 min, and dosage of 2 g for biosorbent pretreated with 1 M of chemical solution. Furthermore, through isotherm and kinetics studies, it was discovered that the biosorption process for untreated biosorbent is by ion exchange, while that for treated biosorbents indicated a multifarious adsorption mechanism. Moreover, the biosorption process was exothermic and spontaneous. Also, it is noted that the sorption capability of the biosorbent increases with pretreatment concentration. A statistical model has been developed with prediction R2 of 0.898, which incorporates the effect of treatment concentration on the percentage removal of As5+ from cassava wastewater. [ABSTRACT FROM AUTHOR]

Alkaline pretreatment can improve the methane yields and dewatering performance of anaerobically digested sludge, but it still needs to be coupled with other conditioning methods in the practical dewatering process. This study utilized four different flocculants and a skeleton builder for conditioning of alkaline pretreatment-anaerobically digested sludge. Chitosan was found to be the most effective in dewatering the sludge. Chitosan coupled with rice husk powder further improved the dewatering performance, which reduced normalized capillary suction time, specific resistance to filtration, and moisture content by 98.7%, 82.0%, and 12.1%. For land use of biogas slurry as a fertilizer, chitosan conditioning promoted the growth of corn seedlings, while the other three flocculants diminished the growth of corn seedlings. Chitosan coupled with rice husk powder further promoted the growth of corn seedlings by 103.5%, 65.0%, and 53.7% in fresh weight, dry weight, and root length, respectively. Overall, chitosan coupled with rice husk powder not only enhanced the dewaterability of alkaline pretreatment-anaerobically digested sludge but also realized the resource utilization of agricultural waste. [Display omitted] • Alkaline pretreatment increased methane yield by 35.2%. • Alkaline pretreatment enhanced the dewaterability of anaerobically digested sludge. • The conditioning effect of chitosan was better than that of other flocculants. • The addition of rice husk powder can further improve the conditioning effect. • Both chitosan and rice husk powder promoted the growth of corn seedlings. [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]

The impact of torrefaction, alkaline pretreatment, and their combination on enzymatic hydrolysis was explored in terms of their effect on glucose yield from wheat straw. Samples were ground and torrefied at varying degrees of process severity, subjected to enzymatic hydrolysis, and analyzed for glucose yield. While glucose yield from raw biomass averaged 190.1 mg per g of dry raw biomass, the yield from torrefied samples was lower, ranging from 0.0 to 63.8 mg g-1, depending on the duration and temperature of the torrefaction process. Alkaline pretreatment increased the glucose yield of raw biomass to an average of 354.9 mg g-1. The highest glucose yield of 359.1 mg glucose g-1 was achieved for samples that were pretreated with a 1% NaOH solution. Alkaline pretreatment after torrefaction but prior to hydrolysis results in glucose yields ranging from 1.2 to 318.2 mg g-1, which are higher than the yields from torrefied-only samples but lower than those of raw, alkaline pretreated samples. When measured on a “per torrefied g” basis, yields of torrefied, alkaline pretreated samples approach those of raw biomass. These results indicate that there may be potential to use torrefaction and hydrolysis together when combined with an alkaline solution pretreatment. [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. [ABSTRACT FROM AUTHOR]

Cassava rhizome is an attractive agricultural residue from cassava-processing industry. With its lignocellulosic structure, cassava rhizome can be converted to simple sugars such as glucose, which is a precursor for succinic acid production. In this study, ozonation and alkaline pretreatments were chosen to enhance liberation of fermentable sugars from cassava rhizomes. Lignin removal and cellulose content were used as the criteria for the pretreatment performance. The maximum lignin removal of 56.47% ww−1 was obtained from alkaline pretreatment under the condition using 2% NaOH at 120 °C and 30 min reaction time, while ozonation pretreatment for 60 min reaction time achieved 18.7% ww−1 lignin removal. The extended reaction time for ozonation did not increase the lignin degradation while the cellulose content slightly increased. Higher concentration of NaOH resulted in decreases on the net weight of cassava rhizome after the pretreatment process. Fermentation of the enzymatic hydrolysate of alkaline-pretreated cassava rhizome led to the maximum succinic acid concentration (11.25 gL−1) and glucose utilization (99.53% ww−1). This study provided an alternative option to convert cassava rhizomes to biochemical products in biorefineries. [ABSTRACT FROM AUTHOR]

The dependency on non-renewable fossil fuels as an energy source has drastically increased global temperatures. Their continuous use poses a great threat to the existing energy reserves. Therefore, the energy sector has taken a turn toward developing eco-friendly, sustainable energy generation by using sustainable lignocellulosic wastes, such as rice straw (RS). For lignocellulosic waste to be utilized as an efficient energy source, it needs to be broken down into less complex forms by pretreatment processes, such as alkaline pretreatment using NaOH. Varied NaOH concentrations (0.5%,1.0%,1.5%,2%) for alkaline pretreatment of RS were used for the holocellulose generation. Amongst the four NaOH concentrations tested, RS-1.5% exhibited higher holocellulose generation of 80.1%, whereas 0.5%, 1 5 and 2% pointed 71.9%, 73.8%, and 78.5% holocellulose generation, respectively. Further, microbial fuel cells (MFCs) were tested for voltage generation by utilizing holocellulose generated from untreated (RS-0%) and mildly alkaline pretreated RS (RS-1.5%) as a feedstock. The MFC voltage and maximum power generation using RS-0% were 194 mV and 167 mW/m2, respectively. With RS-1.5%, the voltage and maximum power generation were 556 mV and 583 mW/m2, respectively. The power density of RS-1.5% was three-fold higher than that of RS-0%. The increase in MFC power generation suggests that alkaline pretreatment plays a crucial role in enhancing the overall performance. [ABSTRACT FROM AUTHOR]

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.